Health

Healthy Weight Calculator for Children by Age and Sex

Q: How much should a 3-year-old weigh?

The average weight (50th percentile) for a 3-year-old is **14.3 kg** (boys) or **13.9 kg** (girls). The healthy range is about **12.5 to 16.5 kg**.

Q: How do I know if my child is overweight?

If your child is above the **85th percentile** on the weight-for-height or BMI-for-age chart, they're at **risk of overweight**. Above the 97th percentile is **obesity**. Talk to your pediatrician.

Q: My child seems underweight—should I worry?

If they're below the **15th percentile** but **have always been there** and are growing normally, it may be constitutional. If they've dropped percentiles or aren't gaining weight, check with your doctor to rule out nutritional or health issues.

Q: Are WHO growth charts used worldwide?

WHO growth charts are **international standards**, based on healthy children from 6 countries. They're the official reference in the US, Argentina, and most countries.

Q: Does weight depend only on diet?

No. It depends on **genetics** (parents' height), **nutrition**, **physical activity**, **overall health**, and **sleep**. An active, well-fed child tends to maintain a healthy weight.

Q: How often should I weigh my child?

At **regular pediatric checkups**: monthly the first year, every 3–6 months until age 3, then annually after. You don't need to weigh your child frequently at home.

Q: Is children's weight gain always linear?

No, growth isn't linear. There are periods of **rapid growth** (height spurts) where kids may look thin, and periods of more weight gain before growth spurts. This is normal and called **adiposity rebound** (around ages 5–6).

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Was this calculator helpful?

Reference values in health come from population studies (NHANES, WHO). They give you a framework to interpret your results, but your personal context matters most. Use this children's weight calculator: enter your child's age and sex to find the healthy weight range based on WHO tables for ages 0–10. Values are updated to 2026 and reviewed regularly to keep you current.

Last reviewed: May 12, 2026 Verified by Hacé Cuentas Team Source: WHO — Reference Values in Health, Mayo Clinic — Trustworthy Medical Information, CDC — Centers for Disease Control and Prevention 100% private

When to use this calculator

You want to know if your child weighs what they should for their age.
Your pediatrician discussed your child's weight and you want to understand the ranges.
You want to compare against official WHO charts.
You're worried your child is above or below healthy weight.
You want a reference for expected weight by age.

Example: 5-year-old boy

Age: 5 years, boy.
Weight (50th percentile): 18.3 kg.
Healthy range (15th–85th percentile): 16–21 kg.

Result: A 5-year-old boy weighs an average of 18.3 kg. The healthy range is 16 to 21 kg (15th to 85th percentile).

How it works

1 min read

Normal health values come from large population studies (NHANES, WHO, CDC). They vary by age, sex, ethnicity, and region. They're guideline-based; your personal medical history always takes precedence.

How It's Calculated

This children's weight calculator uses WHO growth data: enter your child's age and sex to find the healthy weight range for ages 0–10.

The calculator applies the formula with the values you enter, checking typical ranges and alerting you to values outside the normal bounds.

Normal Reference Values

Parameter	Normal Adult Range
Blood pressure	<120/80 mmHg
Heart rate at rest	60–100 bpm
Temperature	36.1–37.2°C
SpO2	95–100%
Fasting blood glucose	70–100 mg/dL
HbA1c	<5.7%
Total cholesterol	<200 mg/dL
LDL	<100 mg/dL
HDL	>40 (M) / >50 (F)

Final Notes

This calculation is a guideline only. For critical decisions (financial, medical, legal), consult a specialist. Values are updated to 2026 and reviewed regularly.

Frequently asked questions

How much should a 3-year-old weigh?

The average weight (50th percentile) for a 3-year-old is 14.3 kg (boys) or 13.9 kg (girls). The healthy range is about 12.5 to 16.5 kg.

How do I know if my child is overweight?

If your child is above the 85th percentile on the weight-for-height or BMI-for-age chart, they're at risk of overweight. Above the 97th percentile is obesity. Talk to your pediatrician.

My child seems underweight—should I worry?

If they're below the 15th percentile but have always been there and are growing normally, it may be constitutional. If they've dropped percentiles or aren't gaining weight, check with your doctor to rule out nutritional or health issues.

Are WHO growth charts used worldwide?

WHO growth charts are international standards, based on healthy children from 6 countries. They're the official reference in the US, Argentina, and most countries.

Does weight depend only on diet?

No. It depends on genetics (parents' height), nutrition, physical activity, overall health, and sleep. An active, well-fed child tends to maintain a healthy weight.

How often should I weigh my child?

At regular pediatric checkups: monthly the first year, every 3–6 months until age 3, then annually after. You don't need to weigh your child frequently at home.

Is children's weight gain always linear?

No, growth isn't linear. There are periods of rapid growth (height spurts) where kids may look thin, and periods of more weight gain before growth spurts. This is normal and called adiposity rebound (around ages 5–6).

Is this calculator free?

Yes, all our calculators are free and don't require registration.