Baby Weight Percentile Calculator
Where your baby's weight sits.
Enter your values
Enter the age in months.
Enter the weight in kg.
Choose one of: Boy, Girl.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Estimated percentile
- 37.1%
- Median weight for age
- 7.9 kg
- Z score
- -0.33
- Difference from median
- -0.3 kg
- Interpretation
- Within typical range
Quick answer
A weight percentile shows the share of babies of the same age and sex who weigh less than yours.
At a glance
| What it does | Where your baby's weight sits. |
|---|---|
| Category | Health |
| Inputs needed | Age, Weight, Sex |
| Main output | Estimated percentile |
| Cost | Free — no sign-up, no download |
How to use the Baby Weight Percentile Calculator
- 1Enter your baby's age in whole months (0–12).
- 2Enter weight in kilograms.
- 3Select boy or girl.
Inputs explained
- Age(months)
- Enter the age in months.
- Weight(kg)
- Enter the weight in kg.
- Sex
- Choose one of: Boy, Girl.
Worked example
Using the values the calculator loads with:
Inputs
- Age6 months
- Weight7.6 kg
- SexBoy
Results
- Estimated percentile37.1%
- Median weight for age7.9 kg
- Z score-0.33
- Difference from median-0.3 kg
- InterpretationWithin typical range
Frequently asked questions
Is a low percentile a problem?
Not on its own — steady growth along a curve matters more than the number.
Is this a medical tool?
No, it is an estimate; your paediatrician uses the full WHO tables.
What do I need to enter into the Baby Weight Percentile Calculator?
Just 3 values: age, weight, sex. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Baby Weight Percentile Calculator work out the answer?
A weight percentile shows the share of babies of the same age and sex who weigh less than yours. The working is shown step by step so you can verify the result by hand.
Is the Baby Weight Percentile Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.