What height range does this family suggest?

The formula, so you can check it

midpoint = (parent A + parent B ± 13 cm) ÷ 2
              (+13 for the male reference, −13 for the female reference)

range    = midpoint − 8.5 cm  to  midpoint + 8.5 cm

Adding 13 cm to the sum before halving is the same as adding 6.5 cm to the average — it is written this way here because that is exactly how the app computes it. Parent heights must be between 100 cm and 230 cm or the calculation is refused rather than guessed.

The ±8.5 cm width is not our invention. It comes from Tanner's parent-adjusted growth standards (Tanner, Goldstein & Whitehouse, Arch Dis Child 1970) and is conventionally described as about two standard deviations — roughly the 3rd to 97th centile, or about 95 children in 100.

A 2024 study argues this width is too narrow and proposes roughly ±9 cm for girls and ±10 cm for boys; we show the conventional figure, so treat this range as the optimistic end.

Nothing here is sent to us or stored

This calculator runs entirely in your browser. The heights you type are never transmitted to us, never written to your device, and are gone the moment you close the page. There is no account, no cookie, no analytics and no tracker on this page.

You can verify that: open your browser's developer tools, look at the network tab, and press the button. Nothing leaves. Our privacy notice says the same thing in full.

What the app adds

For ages 13 to 17½, the Centile app also gives a personal estimate using the Khamis–Roche method, which takes the child's own current height and weight into account rather than only their parents. It comes with its own stated margin of error and a full list of what it cannot tell you.

Read exactly how both calculations work before you decide whether to trust either of them.