How is child height predictor calculated?

The Child Height Predictor substitutes your inputs (Father height (cm), Mother height (cm)) into the standard expression: Boy (cm) = (Father height (cm) + Mother height (cm) + 13) ÷ 2; Girl (cm) = (Father height (cm) + Mother height (cm) − 13) ÷ 2. Every variable is read straight from the fields on this page, and the result is computed the moment you enter the values.

1. 1

   Step 1

   Enter your weight, height, and age as required.

2. 2

   Step 2

   Hit "Calculate" and the result is computed automatically.

3. 3

   Step 3

   Save or share the result as needed.

4. 4

   Step 4

   Review the breakdown: the result repeats the page's own expression (Boy (cm) = (Father height (cm) + Mother height (cm) + 13) ÷ 2; Girl (cm) = (Father height (cm) + Mother height (cm) − 13) ÷ 2) with your values substituted, so each variable stays traceable.

5. 5

   Step 5

   Compare scenarios by varying a single value per run in the child height predictor — that isolates which of the formula's inputs actually drives the result.

• 1

  The Child Height Predictor needs every variable in consistent units — Father height (cm), Mother height (cm) — before the standard formula returns a valid result, so check each field's unit before entering values copied from elsewhere.

• 2

  For repeated what-if work on Child Height Predictor, change one input at a time and note the effect; that isolates which variable actually drives the result instead of moving several values at once and losing the attribution.

• 3

  Read implausible results with suspicion: if the Child Height Predictor output sits orders of magnitude away from your expectation, re-read the inputs — a misplaced decimal or two swapped fields explains most nonsensical answers.

• Father height (cm) and Mother height (cm) must be entered in one consistent unit system: months against years skews the Child Height Predictor result silently. Convert every input to the unit named on its field first.

• Zero and negatives can sit outside the formula's domain: zero mother height (cm) may make the Child Height Predictor undefined, and a negative father height (cm) still returns a number. Check each input is inside the range the quantity allows.