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Pregnancy Weight Gain Calculator

Check your recommended pregnancy weight gain range based on your pre-pregnancy BMI and current week.

Result

11.5–16.0 kg
22.0
Normal weight
5.0 kg

How it is calculated

The tool first finds the pre-pregnancy body mass index, BMI = weight (kg) / height (m)2, with height entered in centimetres. The BMI picks a recommended total gain range for the whole pregnancy: under 18.5 is 12.5–18.0 kg, 18.5 to under 25 is 11.5–16.0 kg, 25 to under 30 is 7.0–11.5 kg and 30 or more is 5.0–9.0 kg. The gain "so far" assumes about 2 kg by week 13, then a steady weekly rate towards the middle of the range at week 40. The week must be 0 to 42. It assumes a single baby and is a general guide, not medical advice for your pregnancy.

Worked example

Height 165 cm, pre-pregnancy weight 60 kg, week 20. BMI = 60 / 1.652 = 60 / 2.7225 = 22.0, which is Normal weight, so the range is 11.5–16.0 kg. The midpoint is 13.75 kg. After 13 weeks 2 kg are expected; the weekly rate afterwards is (13.75 − 2) / 27 ≈ 0.44 kg. At week 20: 2 + 7 × 0.44 ≈ 5.0 kg gained so far.

Try this example →

Common mistakes

  • Entering the current weight instead of the weight before pregnancy; the BMI category must come from the starting weight.
  • Entering height in metres or inches while the field expects centimetres.
  • Expecting the gain to be even each week; the pattern here is slow in the first trimester and faster afterwards.
  • Using the numbers for twins or a pregnancy with medical complications, where targets differ.

About this calculator

This calculator estimates a healthy total weight gain range during pregnancy using the Institute of Medicine (IOM) guidelines, which set different recommended ranges depending on your pre-pregnancy BMI category — underweight, normal weight, overweight or obese.

Expecting mothers and the obstetric providers and midwives who monitor them use these ranges as a general guide, since gaining too little or too much has been linked to different pregnancy risks. Enter your height, pre-pregnancy weight and current week to see your BMI category, target range, and roughly how much you should have gained by now.

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