Calculators that show their working.
Free, interactive tools for the US, UK, Canada and Australia. Each one is a complete engine — charts, export and cited sources — not a single number and a wall of ads.
Available now
- Mortgage calculator
Full PITI payment, PMI, amortization schedule and extra-payment savings.
United States - Compound interest calculator
Growth chart, regular contributions, compounding frequency and inflation-adjusted real value.
United States - Income tax calculator
2026 federal brackets with a per-bracket breakdown, marginal vs effective rate and filing-status comparison.
United States - Paycheck calculator
Salary or hourly take-home pay after federal, FICA and state tax, with a full per-paycheck breakdown.
United States - Auto loan calculator
Per-state sales-tax engine, trade-in tax credit, negative equity and 2026 rates by credit score.
United States - Sales tax calculator
Auto-fills the 2026 rate by state, reverses tax from a total, and splits state vs local.
United States - Percentage calculator
Five modes on one page with the working shown for your exact numbers — no Calculate button.
United States - BMI calculator
Visual WHO gauge, your healthy weight range in lb and kg, and how far you are from it.
United States - Loan calculator
Payment, total interest, amortization with CSV export, and an extra-payment payoff savings mode.
United States - TDEE calculator
BMR and daily calories via Mifflin-St Jeor, goal-based targets and a macro breakdown.
United States - Age calculator
Exact years, months and days, age in every unit, birth weekday and next-birthday countdown.
United States - GPA calculator
Weighted and unweighted GPA side by side on the 4.0 scale, with unlimited courses.
United States - Hours calculator
Weekly time card with break deduction, overnight shifts, automatic overtime and pay.
United States - Tip calculator
Preset percentages, per-person bill splitting and round-up, with US tipping norms.
United States - 401(k) retirement calculator
Employer-match modeling, today's-dollars projection, growth chart and 2026 IRS limits.
United States - Body fat calculator
US Navy method with ACE category gauge, plus fat and lean mass in lb and kg.
United States - Fraction calculator
Add, subtract, multiply or divide fractions with the steps shown and the answer simplified.
United States - Square footage calculator
Room-by-room builder that totals any shapes, with waste factor, material cost and ft²/yd²/m²/acres.
United States - Ideal weight calculator
Devine, Robinson, Miller and Hamwi in lb and kg, the Peterson equation, and your healthy BMI range.
United States - Inflation calculator
Official CPI-U series 1913–2026: equivalent dollar value, cumulative and annualized inflation, chart.
United States - Property tax calculator
Average effective rate by state for 2026, homestead exemptions, monthly escrow and your state's median bill.
United States - Concrete calculator
Slabs, footings, walls and columns in cubic yards, 40/60/80 lb bag counts, 10% overage and cost — multi-element total.
United States - Savings calculator
Project savings to a future value, or set a goal and find the monthly amount needed, with a growth chart.
United States - Grade calculator
Weighted course grade and letter, plus the exact grade you need on the final to reach your target.
United States - Days between dates calculator
Days, weeks, months and years between two dates at once, with true business days and an exact breakdown.
United States - Investment calculator
Lump sum plus monthly or yearly contributions, inflation-adjusted real value, two-scenario compare and a downloadable schedule.
United States - Gold calculator
Melt value of gold, silver and platinum by weight, karat and editable spot price, with dealer payout % and price per gram by karat.
United States - Date calculator
Add or subtract years, months, weeks and days — or business days — from a date, with the result weekday, 30/60/90 presets and .ics export.
United States - Roofing calculator
Footprint and pitch to true roof area, roofing squares and shingle bundles, with live slope factor, waste, material cost and a roof diagram.
United States - Cubic feet calculator
Volume in cubic feet from any mix of inches, feet, yards, cm and metres — boxes, cylinders and area×height, multi-item totals, cost and exact cu yd/m³/litre/gallon conversions.
United States - Rounding calculator
Round to any place from millions to millionths, significant figures or the nearest 0.25 — 9 rounding modes explained, exact decimal maths (0.145 rounds to 0.15) and a number line.
United States - Surface area calculator
Total, lateral and base surface area for 11 shapes — sphere, cylinder, cone, pyramid, prism and more — with the working shown, open/closed variants and honest error bounds.
United States - Average calculator
Mean, median, mode, range, geometric mean and standard deviation from any pasted list — with the working shown for every statistic, plus a weighted average mode.
United States - Steps to miles calculator
Steps to miles and km — personalised from your height and pace (Barreira 2010, ACSM), or an honest range across the three common conventions, plus what research actually says about 10,000 steps.
United States - One rep max calculator
Your 1RM as an honest range across all 7 published formulas (Epley, Brzycki and more, per LeSuer 1997), with the NSCA %1RM training-load table in lb and kg.
United States - Dividend calculator
Income snapshot, a year-by-year DRIP reinvestment projection, and real 2026 qualified dividend tax brackets plus the 3.8% NIIT by filing status.
United States - Stamp duty calculator
SDLT, LBTT and LTT on one page — England & NI, Scotland and Wales compared side by side, with first-time buyer relief, the additional-property surcharges and the non-resident 2%.
United Kingdom - Zakat calculator
Zakat at 2.5% on your zakatable wealth, checked against both the gold and silver nisab (dated UK charity values, editable), with deductible debts handled correctly.
United Kingdom - Height calculator
Predict a child's adult height as an honest range from both parents' heights (Tanner mid-parental method, ±8.5 cm), plus an exact ft/in ↔ cm converter.
United Kingdom - Square meter calculator
Room-by-room floor area in m² from any mix of mm, cm, m, feet and inches — with wastage, packs-needed rounding, cost per m² and exact m²-to-sq-ft conversions.
United Kingdom - BTU calculator
Radiator size for any room as an honest BTU range — room type, glazing, walls and aspect — with watts, the Delta-T50 rule for reading radiator listings, and when you need a proper heat-loss survey.
United Kingdom - Child maintenance calculator
The statutory CMS formula (April 2026) with every step shown — rate band, other children in your household, shared-care nights compared side by side, and the £3,000/week cap.
United Kingdom - Annuity calculator
Estimate the yearly income a pension pot could buy, from dated UK benchmark rates by age and product type — with the 25% tax-free lump sum and a level vs escalating breakeven.
United Kingdom - Mortgage overpayment calculator
Interest saved and years knocked off your term from regular and one-off overpayments, with a 10% allowance check and a balance chart.
United Kingdom - Pro rata calculator
Full-time salary to pro-rata pay by hours or days — annual, monthly, weekly, hourly and daily — plus pro-rata holiday and term-time support.
United Kingdom - Annual leave calculator
UK statutory holiday entitlement (5.6 weeks, 28-day cap) in days and hours, pro-rata for part-time and part-year, plus the 12.07% irregular-hours method. AU page covers the NES 4-week accrual.
United Kingdom - Buy-to-let mortgage calculator
Maximum borrowing from the ICR stress test, interest-only vs repayment, gross and net rental yield, the 5% stamp duty surcharge and cash-on-cash ROI — all in one.
United Kingdom - Dividend tax calculator
Your UK dividend tax for 2026/27 band by band, the £500 allowance, your effective rate, and how much extra the April 2026 rate rise costs vs 2025/26.
United Kingdom - Take-home pay calculator
2026/27 UK net pay from salary or hourly rate: rUK vs Scottish tax bands, National Insurance, student loans, pension salary sacrifice and the £100k Personal Allowance taper.
United Kingdom - Hourly wage calculator
Hourly rate to annual, monthly and weekly salary (and back), checked against the April 2026 National Living Wage and Real Living Wage, with an optional 2026/27 take-home estimate.
United Kingdom - Sales tax calculator (GST/HST/PST)
GST, HST, PST and QST by province for 2026, with a federal-vs-provincial breakdown. Add or remove tax from any amount.
Canada - Income tax calculator
2026 take-home pay by province: federal and provincial tax, CPP/QPP and EI/QPIP, a per-bracket breakdown and a province-by-province comparison.
Canada - CRS calculator
Your Express Entry score from the full IRCC grid (June 2026) with every section shown — core factors, spouse trade-off, skill transferability caps, the +600 PNP — checked against recent draw cutoffs.
Canada - CPP calculator
What your CPP pension pays at any start age from 60 to 70 — the exact −0.6%/+0.7% monthly adjustments, 2026 maximum and average amounts, and an interactive breakeven-age chart.
Canada - TFSA calculator
Your 2026 TFSA contribution room from the full CRA limit table ($109,000 lifetime), with withdrawal re-add rules done right, plus a tax-free vs taxable growth projection.
Canada - GST calculator
Add or remove Australia's 10% GST (the ÷11 rule), with a pre-GST and GST breakdown and the GST-free list.
Australia - Stamp duty calculator
Transfer/land transfer/conveyance duty by state for 2025-26, with first-home concessions, the foreign-buyer surcharge and a state-by-state comparison.
Australia - Income tax calculator
2026-27 take-home pay: the new 15% bracket, the 2% Medicare levy, LITO, the reformed marginal HELP/HECS repayment and 12% super, with a per-bracket breakdown.
Australia - Term deposit calculator
Term deposit interest the way Australian banks actually pay it (simple, at maturity) — plus the after-tax return at your 2026-27 marginal rate that no bank calculator shows.
Australia - Child support calculator
The statutory Formula 1 assessment (2026 rates) with all 8 steps shown — both parents' incomes, the Costs of the Children table, care and cost percentages, and who pays whom.
Australia - Capital gains tax calculator
The extra tax a gain actually costs you at your real 2026-27 marginal rate + Medicare levy, with the 50% discount, loss offsets applied in the correct ATO order, and a per-bracket breakdown.
Australia - Super calculator
Project your super balance to retirement in today's dollars: 12% SG, 2026-27 contribution caps, salary sacrifice and after-tax top-ups, with adjustable fees and returns.
Australia - Novated lease calculator
Vendor-neutral novated lease savings with the FBT, ECM and GST maths shown in full — including the electric-car FBT exemption under the $91,661 cap and the RFBA catch.
Australia - Gravel calculator
Cubic yards and tons of gravel, crushed stone, pea gravel or sand from area and depth, with cost estimate.
United States - Flooring calculator
Square footage across multiple rooms, waste factor by install pattern, boxes needed and total cost.
United States - Volume calculator
Volume of cubes, prisms, cylinders, spheres, cones, pyramids and capsules in metric or imperial units.
United States - Triangle calculator
Solve any triangle from SSS, SAS, ASA, AAS or SSA — sides, angles, area, perimeter and heights, ambiguous case included.
United States - Stair calculator
Riser height, tread depth, step count and stringer length from total rise, checked against NBC residential limits.
Canada - Discount calculator
Sale price from percent off or amount off, stacked discounts done right, and optional sales tax.
United States - Margin calculator
Gross margin, markup and the difference between them — solve for price, cost or margin in any direction.
United States - Z-score calculator
Standard score from x, mean and SD, converted to percentiles and left/right/between probabilities.
United States - Confidence interval calculator
CI for a mean or proportion at 90/95/99 percent, using z or Student t for small samples.
United States - Standard deviation calculator
Population and sample standard deviation, variance and mean with the full step-by-step formula.
United States - Shoe size converter
US, UK, EU and CM (Mondopoint) shoe sizes for men, women and kids, including youth-to-women conversion.
United States - Bra size calculator
Band and bust measurements to US and UK bra sizes, with sister sizes and the UK cup divergence beyond D explained.
United States - Ring size calculator
Circumference or diameter in mm to US, UK letter and EU (ISO 8653) ring sizes, with a string-and-ruler method.
United States - Jeans size converter
Waist measurements to US women's jeans sizes (00-24), EU sizes and the reality of vanity sizing.
United States - Watts to amps calculator
DC, single-phase and three-phase AC conversions with power factor and common US voltages.
United States - Voltage drop calculator
NEC-based drop for copper or aluminum by AWG size, with the 3 percent branch-circuit recommendation check.
United States - kWh calculator
Wattage and hours of use to kWh and monthly cost, preloaded with the latest EIA average residential rate.
United States - Due date calculator
Estimated due date from LMP (Naegele rule), conception date or IVF transfer, with trimester milestones.
United States - Dog pregnancy calculator
A 63-day canine gestation timeline from mating or ovulation, week by week.
United States - Dog age calculator
Human-age equivalent using the 2020 epigenetic formula and size-adjusted veterinary tables, versus the old times-7 rule.
United States - Protein calculator
Daily protein needs in g/kg by goal and activity level, in kg, pounds or stones.
United Kingdom - Pace calculator
Pace, speed and finish time across 5K to marathon, a Riegel race predictor and a full pace chart.
United States - Period calculator
Next-period and estimated fertile-window dates from your cycle length — a date tool, not a contraceptive method.
United Kingdom - Credit card interest calculator
Months to payoff and total interest at your APR, including the minimum-payment trap and extra-payment scenarios.
United States - Salary to hourly calculator
Annual, monthly, weekly and hourly pay converted both ways, with unpaid-vacation adjustments.
United States - Slope calculator
Rise over run to percent grade, degrees and ratio, two-point slope with the line equation, and ADA ramp checks.
United States - Time duration calculator
Exact duration between two times or datetimes, decimal hours, overnight spans and duration math.
United States - GPA converter
Convert between 4.0, 4.3, 5.0 weighted scales, percentages and letter grades.
United States - Roth IRA calculator
Tax-free growth with 2026 IRS contribution limits and MAGI phase-outs, versus a taxable account.
United States - Car tax calculator
UK VED for 2026/27 — first-year rate by CO2, standard rate and the expensive-car supplement, EVs included.
United Kingdom - Self-employed tax calculator
Income tax and Class 4 National Insurance on your profits for 2026/27, with payments on account explained.
United Kingdom - Maternity pay calculator
Statutory Maternity Pay week by week — 90 percent for 6 weeks then the 2026/27 flat rate, with eligibility checks.
United Kingdom - Redundancy calculator
Statutory redundancy pay from your age, service and weekly pay, with the 2026/27 caps applied year by year.
United Kingdom - UCAS points calculator
Official UCAS Tariff points for A-levels, BTECs, T-levels, Scottish Highers and IB.
United Kingdom - Long division calculator
Quotient and remainder with the full long-division layout worked digit by digit — bring down, multiply, subtract at every step, decimals optional.
United States - Ratio calculator
Simplify ratios with Euclid's GCD shown step by step, solve A:B = C:x proportions, scale to a total, and convert ratio to fraction and percent.
United States - Significant figures calculator
Counts sig figs citing the exact rule applied to each zero, rounds to n significant figures digit-exact, and applies the multiplication and addition rules.
United States - Quadratic formula calculator
Roots of ax²+bx+c with the discriminant, simplified radicals, complex roots as a±bi, vertex and factored form — every algebra step written out.
United States - Factoring calculator
Integer factors, prime factorisation, GCF and LCM, plus trinomial factoring by the AC method with difference-of-squares and perfect-square detection.
United States - Pythagorean theorem calculator
Hypotenuse or missing leg in exact simplified-radical and decimal form, Pythagorean-triple check, and the triangle's area and perimeter.
United States - Matrix calculator
Add, multiply, transpose and invert matrices up to 4×4, with cofactor-expansion determinants and Gauss-Jordan steps shown row by row.
United States - Eigenvalue calculator
Eigenvalues and eigenvectors for 2×2 and 3×3 matrices with the characteristic polynomial derived step by step and trace/determinant checks.
United States - Binomial distribution calculator
P(X=k), cumulative and range probabilities with the formula substituted in full, a distribution table, and the normal approximation when valid — exact to n=1000.
United States - Derivative calculator
Symbolic derivatives of elementary single-variable functions to third order, naming the rule applied at every node — power, product, quotient, chain, trig, exp and log.
United States - Trigonometry calculator
Solves right triangles from any two known values with SOH-CAH-TOA steps, degrees and radians, and exact unit-circle values for the special angles.
United Kingdom - Balancing chemical equations calculator
Balances chemical equations by exact-fraction Gaussian elimination on the stoichiometric matrix, with per-element atom counts and a final verification.
United States - CMHC insurance calculator
Mortgage default insurance premium from the CMHC schedule — LTV band, 30-year surcharge, provincial premium tax and the true loan-plus-premium total.
Canada - 407 ETR toll calculator
Trip cost on Highway 407 ETR from the 2026 light-vehicle rate chart — 12 zones, entry-time bands, direction, trip and camera charges, off-peak comparison.
Canada - Mortgage penalty calculator
Estimates a Canadian prepayment penalty three ways — three months' interest, simple IRD and big-bank posted-rate IRD — using the FCAC rules.
Canada - Land transfer tax calculator
Land transfer tax or registration fees in 12 Canadian jurisdictions with first-time-buyer rebates, non-resident surtaxes and a cross-country comparison.
Canada - GST/HST credit (CGEB) calculator
Your Canada Groceries and Essentials Benefit — the renamed GST/HST credit, +25% since July 2026 — from family status, children and adjusted net income.
Canada - Fuel tax credit calculator
ATO fuel tax credits for the current period across six fuel types and both business uses, with the BAS-ready amount and the temporary excise cut applied.
Australia - Tyre size calculator
Compares two tyre sizes — diameter, sidewall, circumference, speedo error at 100 km/h and revs per km — and flags differences beyond the ±3% workshop convention.
Australia - Mortgage offset calculator
Interest saved and years cut from an Australian home loan by an offset account balance, with a with/without schedule and a sensitivity table.
Australia - Child Care Subsidy calculator
Your CCS percentage and out-of-pocket gap fee from family income, care type and hourly fee — including the higher rate for second and younger children aged 5 or under.
Australia - Family Tax Benefit calculator
FTB Part A and Part B per fortnight and per year from the Services Australia rates and both income tests, with the end-of-year supplements listed separately.
Australia - Postage calculator
Australia Post domestic letter and Parcel Post flat-rate prices effective 1 July 2026, satchel versus postage-only, with the Express Post comparison.
Australia - Rent affordability calculator
Maximum sustainable weekly rent from your income at the 30% housing-stress benchmark, mapped against June 2026 median rents in all eight capitals.
Australia - Cubic yard calculator
Cubic yards for rectangular, circular and triangular areas, with truckloads, bag counts and material weight from real density tables.
United States - University grade calculator
Credit-weighted module averages, year weightings and UK degree classification (First, 2:1, 2:2, Third) — plus the mark you need on remaining credits.
United Kingdom - Typing test
15 to 120-second typing test on real sentences: gross and net WPM, accuracy and a consistency score, using the standard 5-character word.
United States - Air fryer conversion
Convert oven temperatures and times to air fryer settings — conventional and fan ovens handled separately — with a per-food UK reference table.
United Kingdom - kJ to calories converter
Instant kilojoule ↔ calorie conversion (1 Cal = 4.184 kJ) with FSANZ-format label examples and the 8,700 kJ daily reference intake.
Australia - Fuel cost calculator
Journey and annual fuel costs from distance, MPG and pence per litre, with return trips, cost per passenger and a petrol vs diesel vs EV comparison.
United Kingdom - Tax refund calculator
ATO 2026-27 refund estimate: PAYG withheld minus your real tax bill (brackets, Medicare levy, LITO and HELP, capped at your remaining balance).
Australia - Mega backdoor Roth calculator
Your 2026 after-tax 401(k) capacity under the $72,000 415(c) limit, with the $8,000 catch-up and the $11,250 super catch-up for ages 60-63.
United States - Pension calculator
Defined-benefit pension from multiplier × service years × final average salary, with early-retirement reductions and a lump sum vs annuity comparison.
United States - Mortgage affordability calculator
Maximum home price from your income and debts under the 28/36 rule, with FHA 31/43 and aggressive presets, PMI and a full PITI breakdown.
United States - Disability tax credit calculator
Retroactive DTC refund estimate up to 10 years, year by year, from real federal and provincial amounts and lowest rates (2016-2026).
Canada - Rent affordability calculator
How much rent you can afford — letting-agent income multiples, the 30% benchmark and the income needed for a target rent.
United Kingdom - Rental yield calculator
Gross and net rental yield with every expense itemized, plus cash-on-cash return if you're buying with a mortgage.
United Kingdom - Prorated rent calculator
Move-in and move-out rent, with the actual-days, 30-day and 365-day methods compared side by side.
United States - Pay stub template
Free Excel and CSV pay stub template with earnings, FICA deductions and net-pay formulas prebuilt.
United States - Land registry fee calculator
Exact HM Land Registry fee from the official Scale 1 and Scale 2 bands, portal vs postal.
United Kingdom - Conveyancing fees calculator
Itemized legal fees and disbursements for buying, selling or remortgaging, with leasehold and new-build supplements.
United Kingdom - Estate agent fees calculator
Commission, VAT and net proceeds — high-street percentage versus online fixed fees, side by side.
United Kingdom - Property tax appeal kit
Texas protest kit: personalized appeal letter, uniform deadlines, evidence checklist and ARB hearing playbook ($49 PDF).
United States
More calculators are shipping each week across all four markets.