What is the average weight for a 1 year old girl?

At 12 months, the WHO median weight for girls is about 9.0 kg, or about 19.8 lb. Many healthy girls naturally sit below or above the median. The more useful question is whether her 12 month old weight percentile matches her length percentile and stays on a steady path over time.

How much should a 1 year old weigh in pounds?

A 1 year old boy is around 21 lb at the WHO median, while a 1 year old girl is around 20 lb. The broader healthy range is much wider than those averages. Percentile position, length, feeding history, and repeated measurements give better context than one pounds-only comparison.

Is my 1 year old underweight?

A low weight percentile does not automatically mean a 1 year old is underweight. Some babies are naturally small and keep a stable curve. Concern rises when weight keeps crossing downward across percentile channels, no longer fits length, or comes with feeding problems, illness, low energy, or fewer wet diapers.

How much weight should a baby gain between 6 and 12 months?

Weight gain usually slows in the second half of the first year. Many babies gain roughly 1.5 to 2.5 kg between 6 and 12 months, but the exact amount varies with birth size, feeding, activity, illness, and genetics. A steady percentile trend matters more than matching a single monthly gain target.

Average Weight for a 1 Year Old

At 12 months, the average weight is about 9.6 kg for boys and 9.0 kg for girls on WHO charts. Use the calculator below to see where a baby's weight sits by percentile, then read it together with length and head circumference.

✓ WHO reference table for 9-15 months
✓ 12 month default calculator
✓ No sign-up — results stay in your browser

Average Weight for a 1 Year Old Calculator

This embedded calculator uses the same infant setup as the baby growth chart calculator: WHO standards, a 0 to 24 month age range, and fields for length, weight, and head circumference. The default age is set to 12 months for a quick 1 year old weight percentile check.

Percentile results

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Interactive charts

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Average Weight for a 1 Year Old Boy and Girl — Reference Table

These WHO weight-for-age rows focus on the months around the first birthday. They are useful for a quick 12 month old weight percentile orientation, but they should not replace the calculator or a pediatric visit because exact percentiles depend on age in days, sex, and repeated measurements over time.

Boys Weight-for-Age WHO

P3 / P50 / P97 reference rows in kg

WHO boys weight-for-age reference values for 9 to 15 months, shown in kilograms.
Age	P3	P50	P97
9 months	7.1	9.2	11.9
10 months	7.4	9.5	12.3
11 months	7.6	9.7	12.6
12 months	7.7	9.6	12.0
13 months	7.9	9.9	12.3
14 months	8.1	10.1	12.6
15 months	8.3	10.3	12.8

Girls Weight-for-Age WHO

P3 / P50 / P97 reference rows in kg

WHO girls weight-for-age reference values for 9 to 15 months, shown in kilograms.
Age	P3	P50	P97
9 months	6.5	8.5	11.0
10 months	6.7	8.7	11.3
11 months	6.9	8.9	11.5
12 months	7.0	9.0	11.8
13 months	7.2	9.2	12.0
14 months	7.4	9.4	12.3
15 months	7.6	9.6	12.5

What Is a Normal Weight for a 1 Year Old?

A normal weight for 1 year old children is better understood as a range than a single target. On WHO charts, the 12 month median is about 9.6 kg for boys and 9.0 kg for girls, while values from roughly P3 to P97 can still be normal. A 12 month old weight percentile becomes more meaningful when it follows a steady path and fits the baby's length, feeding pattern, and overall health.

Why Weight Percentile Matters More Than a Single Number

A 1 year old weight percentile describes relative position, not a score. A baby near the 10th percentile simply weighs more than about 10% of the reference group and less than about 90%. When asking how much should a 1 year old weigh, compare weight with length percentile and the previous curve. A small but steady baby can be just as reassuring as one near the median.

How Weight Changes in the First Year

Baby weight gain first year patterns are usually fastest early on. Many babies double birth weight by around 5 months and are near triple birth weight by 12 months, although birth size and feeding history change the exact path. Growth naturally slows in the second half of the year. A 1 year old weight chart helps show that slower gain can be expected rather than automatically concerning.

When to Talk to Your Pediatrician About Weight

When to worry about 1 year old weight depends on pattern and context. Talk with your pediatrician if weight repeatedly crosses two percentile channels, drops away from length percentile, rises unusually fast, or changes with poor feeding, illness, low energy, or fewer wet diapers. This calculator is an educational screening tool only. It does not replace medical advice, diagnosis, or individualized growth review from a clinician.

Medical disclaimer

Growth chart results are educational and depend on measurement quality, age, sex, and reference standard. Ask a pediatric clinician about persistent percentile changes or any concern about feeding, development, hydration, or illness.

Frequently Asked Questions

These answers cover common parent questions about average 1 year old weight, pounds conversions, underweight concerns, and expected weight gain before the first birthday.

At 12 months, the WHO median weight for boys is about 9.6 kg, or about 21.2 lb. That is the 50th percentile, not a target every child needs to hit. A boy can be healthy below or above that point if his length, feeding, development, and weight trend stay clinically reassuring.

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Average Weight for a 1 Year Old

Average Weight for a 1 Year Old Calculator

Average Weight for a 1 Year Old Boy and Girl — Reference Table

Boys Weight-for-Age WHO

Girls Weight-for-Age WHO

What Is a Normal Weight for a 1 Year Old?

Why Weight Percentile Matters More Than a Single Number

How Weight Changes in the First Year

When to Talk to Your Pediatrician About Weight

Frequently Asked Questions

What is the average weight for a 1 year old boy?−

What is the average weight for a 1 year old girl?+

How much should a 1 year old weigh in pounds?+

Is my 1 year old underweight?+

How much weight should a baby gain between 6 and 12 months?+

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