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Baby Weight Tracker

Plot your baby's weight over time and see whether their weight gain is on track. Your data stays in your browser - and you can download it to keep, then re-upload it any time.

A gentle note. This is a guide, not a medical assessment. Health visitors track growth using the centile charts in your baby's red book. Speak to your health visitor, midwife, GP or a feeding consultant if you're ever worried. It's completely normal for babies to lose a little weight in the first days (most lose around 5-7%)[1] and regain their birth weight by about 3 weeks[2]. A loss of more than 10% of birth weight in the early days should be checked by your midwife or health visitor[3] - so add your baby's birth weight below and we'll flag it for you.

Your baby

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Weight-for-age (WHO centiles)

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The curved lines are the WHO weight-for-age centiles used in the UK red book (2nd, 9th, 25th, 50th, 75th, 91st, 98th). It's very common - and often completely normal - for a baby to change the centile they're tracking on as they settle into their own pattern. This tool doesn't offer guidance on what your baby's weight means - if you're ever concerned about their weight or feeding, please check with your health visitor, midwife, GP or a feeding consultant.

Weigh-ins

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weight-for-age vs the WHO standard
Colour guide: ● On track - gaining at least the expected amount for their age (see the table in the FAQ); ● Below expected - gaining less than that, worth checking with your health visitor. The first 2 weeks aren't colour-judged (early dips are normal) - instead we mark the weigh-in where your baby gets ★ back to their birth weight, and flag if they keep losing after the first few days. A loss of more than 10% of birth weight shows red in the table and in a banner at the top (enter the birth weight above so we can check this).

FAQ

Centile or z-score - what's the difference?

A centile (percentile) tells you how many babies out of 100 weigh less: the 50th is the median (middle), the 9th means about 9 in 100 weigh less. A z-score (or SD score) measures how many standard deviations your baby is from the median: 0 is right on the median, +1 and -1 are roughly the 84th and 16th centiles, and +2/-2 are about the 98th and 2nd. Z-scores are handy at the extremes, where centiles bunch up. You can toggle between modes.

Where do these lines come from?

They're the WHO Child Growth Standards. These are international standards from the WHO Multicentre Growth Reference Study, which followed around 8,500 healthy children growing in optimal conditions across six countries: Brazil, Ghana, India, Norway, Oman and the USA. Because the study chose healthy, well-fed children, the charts describe how children should grow (a standard). The UK red book uses these WHO charts from 2 weeks of age. WHO weight-for-age.

Do breastfed and formula fed babies grow differently?

The WHO charts consider breastfeeding as the norm. In the study used to derive the centiles, children were predominantly breastfed for at least 4 months and still breastfeeding at a year. Breastfed babies typically gain more slowly than formula-fed babies, then after about 3 months; formula-fed babies tend to gain faster. On these charts a formula-fed baby may track a higher centile. What matters most is that your baby keeps roughly following their own curve. More (CDC).

How much should my baby gain a day?

It changes according to age and your baby's current weight. When breastfeeding, once your milk is in (typically around day 3-5), newborns often gain about 20-35 g a day, and roughly 140-245 g a week for the first 3 months, then it slows through the year. More (LLL Canada).

How are the colour flags calculated?

The colours compare your baby's daily weight gain since the last weigh-in with a typical minimum for their age. It's a rough guide - your baby keeping to their own centile line (above) is a better indicator over time.

Age"On track" fromTypical gain
0-3 months~20 g/day20-35 g/day (140-245 g/week)
3-6 months~14 g/day~100-150 g/week
6-12 months~10 g/day~70-90 g/week
12-24 months~5 g/day~40-65 g/week

On track = gaining at least the "on track from" figure for their age; Below expected = gaining less than that - worth checking with your health visitor. The first two weeks aren't colour-judged (early dips are normal); instead we mark with a ★ star the weigh-in where your baby regains their birth weight, and show a red flag if they lose more than 10% of birth weight, or keep losing after the first few days.

Ranges from the WHO growth standards (as used by the NHS) and La Leche League Canada. Individual babies vary widely, and gain depends on your baby's own curve as well as their age.

About the guidance. Typical gains used here: 0-3 months ~150-200g/week, 3-6 months ~100-150g/week, 6-12 months ~70-90g/week (WHO growth standards, as used by the NHS). Individual babies vary widely.

References

  1. North Bristol NHS Trust. Weight loss - typical newborn weight loss is around 5-7% of birth weight.
  2. NICE. Faltering growth: evidence review - weight loss in the early days of life - birth weight usually regained within ~2 weeks; 3 weeks allowed as good practice.
  3. NICE. Faltering growth (NG75) - a loss of more than 10% of birth weight needs a feeding assessment and management plan.

Disclaimer. General information, not medical advice. If you're concerned about your baby's weight or feeding, always check with your health visitor, midwife, GP or a feeding consultant.

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