Weight Percentile Calculator for Kids
The weight percentile calculator shows how a child's weight compares with others of the same sex and age using the CDC weight-for-age charts (ages 2 to 20). Enter age, sex and weight to see the percentile, z-score, median weight and the 3rd to 97th percentile range. For under-2s use the baby growth tool.
Type the problems from this lesson and check each step.
Show steps
How to use the Weight Percentile Calculator for Kids
- Select boy or girl.
- Enter the child's age in years plus extra months (2 to 20 years).
- Enter the weight and choose kilograms or pounds. Height is optional and only used to show BMI.
- Press Calculate to see the percentile, z-score and the median and range for that age.
Formula and method
The CDC gives L, M and S values for weight-for-age at each half-month of age from 2 to 20 years. The calculator interpolates them to the exact age, then uses z = ((weight / M)L − 1) / (L × S). The percentile is the normal distribution function of z times 100. Weight is skewed to the right (a few children are much heavier than average), which is why L is negative and the formula includes the power term.
Weight by age for boys: 3rd to 97th percentile
Weight at key percentiles from the CDC LMS tables.
| Age | 3rd pct | 25th pct | 50th (median) | 75th pct | 97th pct |
|---|---|---|---|---|---|
| 2 years | 10.4 kg (22.9 lb) | 11.8 kg (26.0 lb) | 12.7 kg (27.9 lb) | 13.6 kg (30.1 lb) | 15.6 kg (34.4 lb) |
| 3 years | 11.8 kg (25.9 lb) | 13.3 kg (29.4 lb) | 14.3 kg (31.6 lb) | 15.5 kg (34.1 lb) | 17.9 kg (39.5 lb) |
| 4 years | 13.2 kg (29.2 lb) | 15.0 kg (33.1 lb) | 16.2 kg (35.8 lb) | 17.6 kg (38.9 lb) | 20.9 kg (46.0 lb) |
| 5 years | 14.8 kg (32.6 lb) | 16.9 kg (37.3 lb) | 18.4 kg (40.5 lb) | 20.2 kg (44.4 lb) | 24.3 kg (53.6 lb) |
| 6 years | 16.4 kg (36.2 lb) | 18.9 kg (41.7 lb) | 20.7 kg (45.6 lb) | 22.8 kg (50.3 lb) | 28.1 kg (62.0 lb) |
| 7 years | 18.2 kg (40.1 lb) | 21.0 kg (46.3 lb) | 23.1 kg (50.8 lb) | 25.6 kg (56.5 lb) | 32.3 kg (71.3 lb) |
| 8 years | 20.0 kg (44.2 lb) | 23.2 kg (51.2 lb) | 25.6 kg (56.5 lb) | 28.7 kg (63.3 lb) | 37.2 kg (82.0 lb) |
| 9 years | 22.0 kg (48.5 lb) | 25.7 kg (56.7 lb) | 28.6 kg (62.9 lb) | 32.2 kg (71.1 lb) | 42.8 kg (94.4 lb) |
| 10 years | 24.1 kg (53.1 lb) | 28.5 kg (62.9 lb) | 31.9 kg (70.4 lb) | 36.4 kg (80.2 lb) | 49.1 kg (108.3 lb) |
| 11 years | 26.5 kg (58.4 lb) | 31.8 kg (70.2 lb) | 35.9 kg (79.1 lb) | 41.2 kg (90.8 lb) | 56.0 kg (123.4 lb) |
| 12 years | 29.3 kg (64.7 lb) | 35.7 kg (78.7 lb) | 40.5 kg (89.2 lb) | 46.6 kg (102.7 lb) | 63.0 kg (138.9 lb) |
| 13 years | 32.8 kg (72.3 lb) | 40.2 kg (88.5 lb) | 45.6 kg (100.5 lb) | 52.4 kg (115.5 lb) | 70.0 kg (154.3 lb) |
| 14 years | 36.9 kg (81.3 lb) | 45.1 kg (99.3 lb) | 51.0 kg (112.4 lb) | 58.3 kg (128.6 lb) | 76.7 kg (169.1 lb) |
| 15 years | 41.3 kg (91.1 lb) | 50.0 kg (110.3 lb) | 56.3 kg (124.1 lb) | 64.0 kg (141.0 lb) | 83.0 kg (183.0 lb) |
| 16 years | 45.6 kg (100.6 lb) | 54.5 kg (120.1 lb) | 60.9 kg (134.3 lb) | 68.8 kg (151.8 lb) | 88.7 kg (195.6 lb) |
| 17 years | 49.2 kg (108.4 lb) | 58.1 kg (128.0 lb) | 64.6 kg (142.4 lb) | 72.7 kg (160.2 lb) | 93.6 kg (206.4 lb) |
| 18 years | 51.6 kg (113.8 lb) | 60.6 kg (133.6 lb) | 67.2 kg (148.1 lb) | 75.5 kg (166.4 lb) | 97.1 kg (214.1 lb) |
| 19 years | 53.2 kg (117.2 lb) | 62.4 kg (137.6 lb) | 69.1 kg (152.4 lb) | 77.5 kg (170.9 lb) | 99.1 kg (218.5 lb) |
| 20 years | 54.0 kg (119.1 lb) | 63.6 kg (140.3 lb) | 70.6 kg (155.6 lb) | 79.2 kg (174.6 lb) | 100.8 kg (222.2 lb) |
Weight by age for girls: 3rd to 97th percentile
The same percentiles for girls.
| Age | 3rd pct | 25th pct | 50th (median) | 75th pct | 97th pct |
|---|---|---|---|---|---|
| 2 years | 10.0 kg (22.0 lb) | 11.2 kg (24.8 lb) | 12.1 kg (26.6 lb) | 13.0 kg (28.6 lb) | 15.0 kg (33.1 lb) |
| 3 years | 11.3 kg (25.0 lb) | 12.8 kg (28.3 lb) | 13.9 kg (30.6 lb) | 15.1 kg (33.2 lb) | 17.9 kg (39.4 lb) |
| 4 years | 12.7 kg (28.0 lb) | 14.5 kg (32.0 lb) | 15.8 kg (34.8 lb) | 17.3 kg (38.2 lb) | 21.1 kg (46.6 lb) |
| 5 years | 14.3 kg (31.5 lb) | 16.4 kg (36.1 lb) | 17.9 kg (39.5 lb) | 19.8 kg (43.7 lb) | 24.8 kg (54.6 lb) |
| 6 years | 15.9 kg (35.1 lb) | 18.4 kg (40.6 lb) | 20.2 kg (44.6 lb) | 22.5 kg (49.7 lb) | 28.7 kg (63.4 lb) |
| 7 years | 17.7 kg (38.9 lb) | 20.6 kg (45.4 lb) | 22.8 kg (50.2 lb) | 25.5 kg (56.3 lb) | 33.2 kg (73.1 lb) |
| 8 years | 19.5 kg (42.9 lb) | 23.0 kg (50.7 lb) | 25.6 kg (56.5 lb) | 29.0 kg (64.0 lb) | 38.3 kg (84.4 lb) |
| 9 years | 21.5 kg (47.4 lb) | 25.8 kg (56.8 lb) | 29.0 kg (63.9 lb) | 33.1 kg (73.0 lb) | 44.3 kg (97.7 lb) |
| 10 years | 23.9 kg (52.7 lb) | 29.0 kg (64.0 lb) | 32.9 kg (72.5 lb) | 37.8 kg (83.4 lb) | 51.1 kg (112.7 lb) |
| 11 years | 26.7 kg (58.8 lb) | 32.7 kg (72.1 lb) | 37.2 kg (82.0 lb) | 43.0 kg (94.7 lb) | 58.4 kg (128.8 lb) |
| 12 years | 29.9 kg (65.9 lb) | 36.6 kg (80.7 lb) | 41.6 kg (91.8 lb) | 48.1 kg (106.1 lb) | 65.6 kg (144.6 lb) |
| 13 years | 33.3 kg (73.3 lb) | 40.4 kg (89.1 lb) | 45.8 kg (101.0 lb) | 52.8 kg (116.4 lb) | 72.1 kg (159.0 lb) |
| 14 years | 36.6 kg (80.6 lb) | 43.8 kg (96.6 lb) | 49.4 kg (108.8 lb) | 56.6 kg (124.8 lb) | 77.5 kg (170.8 lb) |
| 15 years | 39.5 kg (87.0 lb) | 46.6 kg (102.6 lb) | 52.0 kg (114.7 lb) | 59.4 kg (130.9 lb) | 81.5 kg (179.7 lb) |
| 16 years | 41.7 kg (92.0 lb) | 48.6 kg (107.0 lb) | 53.9 kg (118.8 lb) | 61.1 kg (134.7 lb) | 84.3 kg (185.8 lb) |
| 17 years | 43.3 kg (95.4 lb) | 49.9 kg (110.0 lb) | 55.1 kg (121.6 lb) | 62.3 kg (137.3 lb) | 86.1 kg (189.8 lb) |
| 18 years | 44.2 kg (97.5 lb) | 50.9 kg (112.2 lb) | 56.2 kg (123.9 lb) | 63.4 kg (139.8 lb) | 87.4 kg (192.7 lb) |
| 19 years | 44.8 kg (98.7 lb) | 51.8 kg (114.2 lb) | 57.3 kg (126.3 lb) | 64.7 kg (142.7 lb) | 88.4 kg (194.9 lb) |
| 20 years | 45.0 kg (99.3 lb) | 52.5 kg (115.7 lb) | 58.2 kg (128.4 lb) | 65.9 kg (145.2 lb) | 89.0 kg (196.3 lb) |
Weight percentile versus BMI percentile
Weight-for-age only tells you how heavy a child is compared with others of the same age. It cannot tell you if that weight is appropriate for height. A tall 10-year-old can be at the 95th percentile for weight and still have a healthy BMI. BMI-for-age compares weight relative to height and is the CDC screening measure for underweight, healthy weight and obesity in children 2 and older. Use the BMI Percentile Calculator for that question.
What is a normal weight percentile for a child?
Anything between the 3rd and 97th percentile is within the usual range on the weight chart. A child at the 15th percentile is not underweight just because the number is low, and a child at the 80th is not overweight just because it is high. Look at whether the child follows a steady curve and whether height and weight are in proportion.
Why a child's weight percentile can change
Growth is not a straight line. Illness, a growth spurt, a change in activity or appetite, and puberty can all shift a child's weight percentile. A change of one or two percentile lines is common; moving across several lines over a year is worth discussing with a doctor.
Weight gain and loss in children
Children are expected to gain weight steadily as they grow, with larger gains during puberty. Unplanned weight loss, a plateau for many months or fast weight gain are all reasons to see a pediatrician. Parents should avoid putting children on diets without medical advice.
How to weigh a child accurately
Use the same scale each time, ideally in the morning before breakfast and after using the toilet, in light clothes and without shoes. Record the weight to the nearest 0.1 kg (or quarter pound). Digital bathroom scales are accurate enough for home tracking; clinic readings can differ slightly.
Reading the z-score
A z-score of 0 is the median. A z-score of −1 is about the 16th percentile and +1 is about the 84th. Values beyond −2 or +2 (below the 2nd or above the 98th percentile) get closer attention from clinicians.
Frequently asked questions
What is a healthy weight percentile for a child?
Between the 3rd and 97th percentile is the usual range on the weight-for-age chart; weight status for overweight or underweight is judged using BMI-for-age.
Is the 90th percentile for weight too high?
Not by itself. It may reflect a tall child. Check the BMI percentile and growth history with a pediatrician.
What weight is the 50th percentile for an 8-year-old?
It is about 25.6 kg (56.5 lb) for both boys and girls in the CDC data. Use the tables above for other ages.
Can I use this for infants?
No. Use the Baby Growth Percentile Calculator with the WHO standards for ages 0 to 24 months.
How accurate is this calculator?
It uses the published CDC LMS values and reproduces the CDC percentile columns to within a fraction of a percentile point. Measurement error in the weight you enter matters more.
Does weight percentile mean the same for boys and girls?
The calculation is the same but boys and girls use separate reference tables.
Sources
- CDC: Growth chart percentile data files with LMS values
- Kuczmarski RJ et al. 2000 CDC Growth Charts for the United States: methods and development (NCHS Vital and Health Statistics, Series 11, No. 246)
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