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Baby & Parenting Calculators

Baby Weight Gain Calculator

Weight gain per day, week and month between two weigh-ins, and the percentage change from birth weight.

Enter values

Results update as you type.

Result

Gain per day

31.7 g

Per week
222 g
Total gain
1,900 g
Increase from birth weight
57.6%

Educational estimate only — not medical advice. Talk to a healthcare professional about your individual situation. Growth is assessed on centile charts by your health visitor or paediatrician.

About the Baby Weight Gain Calculator

Weight gain per day, week and month between two weigh-ins, and the percentage change from birth weight.

Also known as: baby growth calculator, infant weight gain, baby growth percentage.

How to use this calculator

  1. Enter birth weight (g), current weight (g), days since birth.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

Gain per day = (current − birth weight) ÷ days

Worked example

Using the values pre-filled in the calculator above:

  • Birth weight (g) = 3,300
  • Current weight (g) = 5,200
  • Days since birth = 60

the calculator returns:

  • Gain per day: 31.7 g
  • Per week: 222 g
  • Total gain: 1,900 g
  • Increase from birth weight: 57.6%