Calculators
Child Age and Milestone Checkpoint Calculator
Calculate a child's age in months, corrected age for prematurity and the next standard developmental milestone checkpoint.
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- Nothing uploaded
The tool
Enter your numbers below. Results update as you type, and nothing leaves your browser.
Everything you enter stays on your own machine. Nothing is sent to us or to anyone else, which you can confirm in your browser network tab.
What people use it for
- Tracking developmental checkpoints
- Parents of premature babies
- Childcare record keeping
- Health visitor and nursery planning
About this tool
What the Child Age and Milestone Checkpoint Calculator does
Developmental milestones are checked at set ages, and for babies born early, corrected age (chronological age minus weeks born early) is generally used until about age two. This calculator works out both ages and the next common checkpoint age used in CDC milestone checklists.
It also works as a child development milestone calculator or a corrected age calculator.
Formula
- Age in months = days since birth ÷ 30.44
- Corrected age = age − weeks born early
- Corrected age is commonly used until about 24 months
Worked example
Using the starting values in the calculator above:
| Input | Value |
|---|---|
| Date of birth | 2025-08-10 |
| Weeks born before 40 weeks | 0 |
| Result | Value |
|---|---|
| Age in months | 14.2 |
| Corrected age in months | 14.2 |
| Next milestone checkpoint | 15 months |
| Age used for milestones | Chronological age |
How to read the result
Milestone checklists describe what most children can do by an age; children develop at different rates.
If a child loses skills they once had, or you have concerns, speak to a health professional rather than waiting for the next checkpoint.
General information only. Discuss any concerns about development with a paediatrician or health visitor.
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Questions
Questions about this tool
The things clients actually want to know — costs, timelines, ownership and what happens after launch.
A premature baby's age adjusted for how early they were born, used for development until about two years.
Commonly at well-child visits such as 2, 4, 6, 9, 12, 15, 18, 24 and 30 months, and yearly after.
Public health bodies such as the CDC publish free checklists by age.
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