Height Calculator
For a boy with a 180 cm father and 165 cm mother, the mid-parental formula (Tanner et al. 1970) predicts an adult height likely between 170.5 cm and 187.5 cm (5'7"–6'2"), midpoint 179 cm. We always show the full ±8.5 cm range — never a single number, unlike some competing calculators. The tool below also converts feet/inches to cm exactly.
170.5 cm–187.5 cm likely adult height (5'7 1/4"–6'1 3/4")
Based on the mid-parental height formula (Tanner et al. 1970), the midpoint estimate is 179 cm (5'10 1/2"), but the method carries a documented spread of ±8.5 cm — so the honest answer is a range: likely between 170.5 cm and 187.5 cm (5'7 1/4"–6'1 3/4").
How this was calculated
| sum = mother's height + father's height = 165 + 180 = 345 | |
| sum + 13 = 345 + 13 = 358 | |
| predicted height = 358 / 2 = 179 cm | |
| Range (±8.5 cm, 2 SD) | 170.5 cm–187.5 cm (5'7 1/4"–6'1 3/4") |
Estimate from parental heights only — genetics, nutrition and health all matter. Speak to your GP or health visitor if you have concerns about a child's growth. Not medical advice.
Child height prediction uses the mid-parental height formula (Tanner et al. 1970), always shown as a ±8.5 cm range, never a single number. An estimate, not a diagnosis or medical advice. How we calculate →
The mid-parental height formula (Tanner, 1970)
The child height predictor above uses the mid-parental height formula, published by James Tanner, Harvey Goldstein and Robert Whitehouse in 1970 (Archives of Disease in Childhood, 45(244):755-762) and still the standard reference method used by clinicians and growth-chart tools today.
For a boy: add the mother's and father's height in cm, add 13, then divide by 2. For a girl: add the two heights, subtract 13, then divide by 2. The 13 cm adjustment accounts for the average height difference between adult men and women in the reference population.
Crucially, the formula was never meant to give a single number. Tanner's own analysis showed the estimate carries a spread of ±8.5 cm — about two standard deviations, or roughly the 3rd-to-97th percentile band of outcomes for children with those parents. We show that full range every time, not just the midpoint, because a bare number implies a precision the formula doesn't have.
Why we show a range, not a single number
Several calculators for this exact search — including the top-ranking one — display one bare centimetre figure and stop there. That's misleading: the underlying statistics were never that precise, and treating a midpoint as a forecast sets parents up for false alarm or false reassurance.
We show the full ±8.5 cm band on every result, alongside the midpoint, and explain what that range means statistically. It's the same honesty standard used by the more clinically framed calculators in this space (which tend to be aimed at professionals) — we've just made it the default for everyone.
The honest limits of this estimate
Two limitations are worth stating plainly, both documented in the peer-reviewed literature on Tanner's formula. First, a 2025 review (Ciancia et al.) found the formula tends to underestimate adult height in children of very short parents — the further the parents are from average, the less reliable the point estimate.
Second, that same review notes that in practice a deviation as large as the full ±8.5 cm only occurs in around 3% of cases for typical families — meaning the classic band, while the standard citable figure, is on the wide/conservative side for most children. We report the standard ±8.5 cm because it's the sourced, peer-reviewed figure, but it's worth knowing which direction the uncertainty tends to run.
More broadly: this formula uses only parental height. It says nothing about a specific child's nutrition, health conditions, puberty timing or growth trajectory — all of which can shift an individual child's actual adult height away from the parental estimate.
Khamis-Roche: a more detailed method we don't (yet) implement
Some calculators also offer the Khamis-Roche method (Khamis & Roche, 1994, Pediatrics), which adds the child's current height, current weight and age (4.0-17.5 years) to the parental-height inputs, using a lookup table of regression coefficients specific to each sex and age. Published sources report it as more precise than mid-parental — roughly ±5.6 cm for boys and ±4.3 cm for girls, versus ±8.5 cm here.
We chose not to build it into this tool yet. The formula's error margins are well documented secondhand, but the full coefficient table (56 rows across sex and age) comes from a paywalled 1994 journal article, and we could only find scattered, unsourced fragments of it on other sites — not a citable primary source we could verify to the standard we hold ourselves to. Rather than copy figures we can't independently confirm into a tool that touches a child's growth, we've shipped the fully sourced mid-parental method for now and will add Khamis-Roche once we can verify the coefficient table against the original paper or another clearly licensed source.
Converting between feet/inches and centimetres
The unit converter tab uses the exact, internationally defined conversion: 1 inch = 2.54 cm exactly (from the 1959 international yard and pound agreement), so 1 foot = 30.48 cm. This is a fixed constant, not an estimate — unlike the height prediction above, there's no error margin to report.
A quick reference: 5'0" = 152.4 cm, 5'4" = 162.56 cm, 5'6" = 167.64 cm, 5'9" = 175.26 cm, 5'11" = 180.34 cm, 6'0" = 182.88 cm, 6'2" = 187.96 cm. The converter above handles any combination and shows the exact figure alongside a value rounded to the nearest quarter-inch for everyday use.
Frequently asked questions
How do I calculate my child's future height?
The most common method is the mid-parental height formula (Tanner, 1970): for a boy, add both parents' heights in cm, add 13, then divide by 2; for a girl, subtract 13 instead of adding it. Enter both parents' heights above and the calculator does this automatically — always shown as a range (±8.5 cm), not a single number.
How accurate are height predictor calculators?
The mid-parental formula has a documented spread of about ±8.5 cm (two standard deviations) around its midpoint, and research shows it tends to underestimate the adult height of children with very short parents. Treat any prediction — from this tool or any other — as a wide statistical range, not a forecast for one specific child.
What is mid-parental height?
Mid-parental height is the average of both parents' heights, adjusted by ±13 cm for the child's sex (added for boys, subtracted for girls) to account for the typical height difference between adult men and women. It's the basis of the standard Tanner (1970) child-height prediction formula used above.
How do you convert feet and inches to cm?
Multiply the total inches (feet × 12 + inches) by 2.54, the exact international conversion factor. For example, 5'9" = 69 inches × 2.54 = 175.26 cm. Use the converter tab above for instant, exact conversions in both directions.
Is height genetic?
Largely, yes — twin and family studies put the heritability of adult height at roughly 80%, which is why parental height is a reasonably useful predictor. But the remaining share comes from nutrition, overall childhood health, and individual variation, which is exactly why any parental-height-based estimate needs a wide error range rather than a single number.
Why is there a range instead of one number for my child's predicted height?
Because that's what the underlying statistics actually support. The Tanner formula's midpoint carries a documented ±8.5 cm spread; showing only the midpoint (as some calculators do) implies far more precision than the method has. We show the full range every time.
Researched & verified by the Calcuris Data & Research Team. How we build and check our tools →