Kids foot growth and shoe change tracker
Works out the foot growth rate from your own measurements, then predicts when the current shoe runs out of room.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter first measurement date, first foot length, second measurement date, second foot length, current shoe insole length and minimum room.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Monthly growth = (second − first measurement) ÷ (days ÷ 30.436875). Months left = (insole − minimum room − second measurement) ÷ monthly growth.
Example
Inputs: First measurement date = 2026-01-01, First foot length = 14 cm, Second measurement date = 2026-07-02, Second foot length = 15 cm, Current shoe insole length = 17 cm. Result: Growth per month: 1.67 mm; Months left in the current shoe: 6; Expected shoe change date: Thursday, December 31, 2026 (2026-12-31).
Limits and caveats
- It assumes growth continues at the same pace, while children grow in spurts.
- A 1 mm measuring error moves the result a lot over short gaps, so leave at least two months between measurements.
Questions about this tool
How often should I measure?
Every two or three months is enough to track growth; measure more often for very young children.
Why 30.436875 days per month?
It is the average Gregorian month (365.2425 ÷ 12), which gives an even monthly rate.
What if it shows 0 months?
The shoe already has less than the minimum room, so it is time for a bigger size.