Baby Weight Chart by Month: WHO Weight-for-Age, Birth to 12 Months

Quick answer

The tables below show the World Health Organization’s weight-for-age percentiles for boys and girls from birth to 12 months.¹ They are reference values, not an individual diagnosis or a target weight.

Use the row for the baby’s completed age and the table that matches the sex category used by the WHO standard. The 50th percentile is the median, not the “best” line. A single plotted point cannot explain feeding, body composition, weight change or overall health. A clinician interprets accurate measurements over time together with length or height, medical history and examination.

In India, the Indian Academy of Pediatrics has recommended WHO growth standards for children younger than five years.² That does not create a separate “Indian baby weight” table or make every value between two percentile lines medically normal.

WHO weight-for-age table: boys

Weights are kilograms. Values are the WHO 3rd, 50th and 97th percentiles rounded to one decimal place.¹

Completed age	3rd percentile	50th percentile	97th percentile
Birth	2.5	3.3	4.3
1 month	3.4	4.5	5.7
2 months	4.4	5.6	7.0
3 months	5.1	6.4	7.9
4 months	5.6	7.0	8.6
5 months	6.1	7.5	9.2
6 months	6.4	7.9	9.7
7 months	6.7	8.3	10.2
8 months	7.0	8.6	10.5
9 months	7.2	8.9	10.9
10 months	7.5	9.2	11.2
11 months	7.7	9.4	11.5
12 months	7.8	9.6	11.8

WHO weight-for-age table: girls

Weights are kilograms. Values are the WHO 3rd, 50th and 97th percentiles rounded to one decimal place.¹

Completed age	3rd percentile	50th percentile	97th percentile
Birth	2.4	3.2	4.2
1 month	3.2	4.2	5.4
2 months	4.0	5.1	6.5
3 months	4.6	5.8	7.4
4 months	5.1	6.4	8.1
5 months	5.5	6.9	8.7
6 months	5.8	7.3	9.2
7 months	6.1	7.6	9.6
8 months	6.3	7.9	10.0
9 months	6.6	8.2	10.4
10 months	6.8	8.5	10.7
11 months	7.0	8.7	11.0
12 months	7.1	8.9	11.3

How to read the table without turning it into a verdict

The percentile describes a position in a reference distribution

If a measurement is near the 50th percentile, it is near the reference median for that age and sex. A lower or higher percentile is not a score for the baby or the parent. The chart does not say what a baby “should” weigh next month.

One point is not a growth trend

Growth monitoring uses repeated, accurately measured points. Apparent movement can reflect age entry, scale variation, clothing, rounding, illness, fluid balance or a real change. Do not infer a diagnosis from a household-scale reading or from one online result.

Weight-for-age is only one indicator

Weight-for-age considers weight, age and sex. It does not use length or height, so it cannot by itself distinguish a shorter child from low weight for length, or assess high weight relative to length. WHO uses length/height-for-age, weight-for-length/height and BMI-for-age as separate indicators.³

This is why an upper weight-for-age percentile must not be labelled “overweight,” and a value between the 3rd and 97th percentiles must not be labelled automatically “healthy” or “normal.” WHO advises measuring both weight and length or height when assessing nutritional status in children younger than five.⁴

Use the baby’s exact age

The monthly table is useful for a quick lookup, but a calculator needs more precision. WHO’s under-five computation uses age in days. A baby’s date of birth and the date of measurement are therefore different inputs; using today’s date for an older measurement changes the result.⁵

For a baby born preterm, do not invent a corrected age in the calculator. Ask the neonatal or pediatric team which age and chart they want used, for how long, and how they want the result documented.

The WHO reference has male and female source tables. A public calculator should describe this as the sex category used by the source, not as a judgment about gender identity. If the relevant reference category is uncertain, leave the calculator and ask the child’s clinician rather than guessing.

Measure weight consistently

The number is only as useful as the measurement. For an infant measurement:

• use an appropriate, stable and calibrated scale;
• follow the scale and clinic instructions;
• remove shoes and heavy clothing, and record what remained on;
• record the measurement date and weight without silently rounding the input; and
• use the clinic measurement when it differs from a rough household-scale reading.

Do not weigh a baby repeatedly to chase a percentile. Ask the child’s clinician how often measurement is useful for that baby’s situation.

Attained weight and weight gain are different questions

The tables above show attained weight at an age. They do not show how much weight a baby gained during a particular interval.

WHO publishes separate weight-velocity standards, including one-month increments from birth to 12 months and short intervals by birth-weight group in early infancy.⁶ Those interval standards should not be replaced with a universal “grams per day” rule. Individual increments can vary substantially between consecutive periods, and the appropriate comparison depends on the actual time between measurements.

This article therefore does not prescribe weekly or monthly gain targets or promise that every baby will double or triple birth weight on a fixed date. Weight gained over an interval is interpreted separately from the attained-weight table.

What to bring to a growth conversation

If you want a clinician to interpret a pattern, bring:

• dates and weights from the child’s health record;
• where and how each measurement was taken;
• birth gestation and birth weight;
• recent illness or major feeding changes;
• available length or height measurements; and
• the concern that prompted you to check.

Do not enter names, medical history or a full measurement record into an SEO calculator. The public tool should calculate locally, retain nothing and create no shareable URL containing health information.

When to seek help

This article deliberately does not turn a percentile, a number of crossed chart lines or a fixed period without gain into an automatic urgency level. Those rules depend on age, measurement quality, the full growth pattern and the child’s condition.

Seek clinical advice when you are concerned about growth, feeding or measurement changes. If a baby appears seriously unwell, use local emergency care rather than waiting for an online chart result.

Common questions

What is the average weight of a 6-month-old baby?

The WHO median in the table is 7.9 kg for boys and 7.3 kg for girls. A median is a reference position, not a target or a diagnosis. Use the exact age and repeated clinical measurements for interpretation.

What does the chart show for 2, 4, 8, 9 or 10 months?

Use the matching row in the boys’ or girls’ table above. Separate month-specific pages would repeat the same dataset and split the search journey, so this one canonical should remain the lookup destination.

Is the 50th percentile ideal?

No. It is the reference median. A clinician does not try to move every child to the middle line.

Is anything between the 3rd and 97th percentile normal?

The table shows those percentile positions; it does not create a diagnosis-free zone. A point inside that interval may still need interpretation, and a point outside it is not a complete diagnosis. Measurement quality, pattern, length or height and clinical context matter.

Can weight-for-age show whether a baby is overweight?

Not by itself. Weight relative to length or height and other clinical context are needed. Do not use a high weight-for-age percentile to restrict feeding.

Which chart is used for children under five in India?

The IAP growth-chart committee states that WHO standards are used for Indian children younger than five, while its revised Indian charts address older children.² The final page should name the exact source instead of saying only “WHO/IAP guidance.”

Should I use corrected age after preterm birth?

Ask the baby’s neonatal or pediatric team. This page and the current calculator do not calculate corrected age and should not claim to know which chart or duration applies to an individual child.

Sources

This article provides general information and does not replace individual medical advice.

Footnotes

1. World Health Organization. Weight-for-age standards: charts and tables, birth to 5 years. Accessed 13 September 2026. The tables in this article use the WHO percentile workbooks linked from that page. ↩ ↩² ↩³

2. Khadilkar V, et al. Revised IAP Growth Charts for Height, Weight and Body Mass Index for 5- to 18-year-old Indian Children. Indian Pediatrics. 2015;52:47–55. The article records adoption of WHO standards for children younger than five. ↩ ↩²

3. World Health Organization. Child growth standards. Accessed 13 September 2026. ↩

4. World Health Organization. Assessing and managing children at primary health-care facilities to prevent overweight and obesity. 2017. ↩

5. World Health Organization. Anthro: computation of the WHO Child Growth Standards. Source repository, accessed at commit b776d8a12b1c97369c748b561159fd2ec4f4db58 on 13 September 2026. ↩

6. World Health Organization. Weight-velocity standards. Accessed 13 September 2026. ↩