Calculate your newborn's weight percentile using WHO growth charts. See where your baby falls compared to age and sex-matched peers from birth to 24 months.
Weight percentiles tell you how your baby's weight compares to other babies of the same age and sex. A baby at the 50th percentile weighs more than 50% of babies and less than 50% — right in the middle. A baby at the 25th or 75th percentile is equally healthy; what matters is consistent growth along their curve.
This calculator uses WHO growth standards (2006), the gold standard for infant growth assessment worldwide. The WHO charts are based on breastfed babies from multiple countries and represent optimal growth. The CDC charts (2000) are sometimes used in the U.S. for comparison.
Pediatricians track percentiles at every well-child visit to identify potential growth concerns early. A single percentile reading is less important than the trend — if your baby consistently tracks along the 30th percentile, that's their normal. Concern arises when a baby crosses two or more major percentile lines (e.g., dropping from 75th to 25th).
Tracking your baby's weight percentile between doctor visits helps you monitor growth patterns and come to appointments informed. This calculator uses the same WHO data your pediatrician uses, giving you reliable results at home. Having a precise figure at your fingertips empowers better planning and more confident decisions. Manual calculations are error-prone and time-consuming; this tool delivers verified results in seconds so you can focus on strategy.
Percentile is calculated using a z-score method: z = (observed weight − median weight for age/sex) / standard deviation WHO LMS method: z = ((weight/M)^L − 1) / (L × S) where M = median, L = power, S = variation coefficient Percentile = normal distribution CDF(z) × 100
Result: 56th percentile — Average range
A 3-month-old girl weighing 10 lbs 4 oz (4.65 kg) falls at approximately the 56th percentile on the WHO weight-for-age chart. This means she weighs more than 56% of 3-month-old girls worldwide. This is well within the average range (25th–75th percentile). If she was at the 50th percentile at birth, tracking to 56th at 3 months shows healthy, stable growth.
Growth charts show percentile curves (3rd, 5th, 10th, 25th, 50th, 75th, 90th, 95th, 97th) that represent the statistical distribution of weight-for-age in a reference population. Your baby's weight is plotted against these curves to determine where they fall relative to peers. The goal is not to be at the 50th percentile — it's to grow consistently along their own curve.
Red flags that warrant discussion with your pediatrician include: weight below the 3rd percentile, weight above the 97th percentile, crossing two or more major percentile lines in either direction, failure to regain birth weight by 2 weeks of age, or weight loss after the initial newborn period. These don't necessarily indicate a problem but deserve professional evaluation.
Breastfed babies typically gain weight more rapidly in the first 3 months but slower from 3–12 months compared to formula-fed babies. This is normal and reflected in WHO charts (which are based on breastfed babies). If your breastfed baby appears to "fall off" the CDC chart at 4–6 months, the WHO chart may show perfectly normal tracking.
Any percentile from 3rd to 97th is considered within the normal range. The 50th percentile is the median (average), not the "ideal." A baby consistently tracking at the 15th or 85th percentile is growing perfectly normally. Concern arises only when a baby's percentile changes dramatically (crossing 2+ major lines) or falls below the 3rd or above the 97th.
WHO growth standards (2006) describe how children SHOULD grow under optimal conditions (breastfed, non-smoking household, standard care), using data from multiple countries. CDC charts (2000) describe how U.S. children DID grow, including formula-fed babies. WHO charts are considered the better standard for 0–2 years; CDC charts are used for 2–20 years in the U.S.
A single percentile line drop (e.g., 60th to 40th) is usually not concerning, especially if it happens gradually over several months. Normal variation, illness recovery, or a growth spurt in length can cause temporary weight percentile changes. However, discuss this with your pediatrician to be safe, especially if the drop continues.
Yes, for growth assessments until age 2. Corrected age = actual age minus weeks premature. A baby born at 32 weeks who is now 4 months old has a corrected age of about 2 months. Use corrected age on growth charts for a fairer comparison, since premature babies need time to "catch up" to full-term peers.
At birth and at each well-child visit (typically 1, 2, 4, 6, 9, 12, 15, 18, and 24 months) is sufficient. Weighing at home every 1–2 weeks is acceptable if it doesn't cause anxiety. Daily weighing is unnecessary and can create stress over normal fluctuations. If you have concerns, your pediatrician can schedule additional weight checks.
Yes, significantly. Two short, slim parents are more likely to have a baby tracking at lower percentiles, while two tall, larger parents are more likely to have a baby at higher percentiles. Birth weight is influenced by maternal factors, but by 6–12 months, the baby's own genetic growth pattern typically asserts itself — which can mean moving to a different percentile line.