Find how much weight you should gain in pregnancy based on your pre-pregnancy BMI, the IOM recommended total range, and whether you are on track at your current week.
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Enter your pre-pregnancy weight, height, current week and current weight. See your pre-pregnancy BMI, the recommended total gain and whether you are on track.
=Recommended total gain
11.5–16kg
Normal · BMI 22
Recommended by this week2.9–5.5 kg
Gained so far6 kg
StatusOn track
Based on the Institute of Medicine (IOM 2009) guidelines for a single pregnancy. These are general ranges, not medical advice — your doctor or midwife may recommend a different target.
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Indicative estimate, not medical advice. This calculator uses the Institute of Medicine (IOM 2009) weight-gain ranges based on your pre-pregnancy BMI. Every pregnancy is different — consult your doctor or midwife. Instant in-browser calculation, no account.
✚ Results are for informational purposes and do not replace medical advice. For health decisions, consult a doctor.
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iHow it is calculated
The Institute of Medicine (IOM 2009) sets how much weight to gain in pregnancy from your pre-pregnancy BMI — weight before pregnancy divided by height squared. That BMI falls into one of four categories, each with its own recommended total gain for a single baby, plus a weekly rate for the second and third trimesters:
pre-pregnancy BMI = weight (kg) ÷ height² (m) → IOM gain range
For 60 kg and 1.65 m: BMI = 60 ÷ (1.65 × 1.65) ≈ 22.0 — normal weight, so the IOM recommends a total gain of 11.5–16 kg over the pregnancy, with about 0.35–0.50 kg per week in the second and third trimesters.
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?Frequently asked questions
How much weight should I gain during pregnancy?
It depends on your pre-pregnancy BMI. The IOM (2009) recommends a total gain of 12.5–18 kg if you were underweight, 11.5–16 kg if normal weight, 7–11.5 kg if overweight and 5–9 kg if obese. This calculator picks the right range from the pre-pregnancy weight and height you enter.
How is the recommended gain calculated?
First your pre-pregnancy BMI is computed as weight divided by height in metres squared. That BMI places you in one of four categories — underweight, normal, overweight or obese — and each category has its own IOM total-gain range for a single baby. For example, 60 kg at 1.65 m gives a BMI of 22 (normal), so the target is 11.5–16 kg.
How much weight should I gain each week?
Most gain happens in the second and third trimesters. The IOM suggests about 0.44–0.58 kg/week if underweight, 0.35–0.50 kg/week if normal weight, 0.23–0.33 kg/week if overweight and 0.17–0.27 kg/week if obese, after a small 0.5–2 kg gain over the whole first trimester. The calculator uses these rates to show what you should weigh by your current week.
Am I on track for my week?
Enter your current week and current weight and the calculator compares your actual gain with the IOM range expected by that point, flagging it as on track, below target or above target. Being slightly outside the band in a single week is normal — the trend over several weeks matters more than one reading.
How much weight should I gain with twins?
Twin pregnancies need more. The IOM provisional ranges for twins are 17–25 kg for a normal pre-pregnancy BMI, 14–23 kg if overweight and 11–19 kg if obese; there is not enough evidence to set an underweight range. This calculator is for a single baby, so ask your doctor for a twin target.
What if I gain too much or too little?
Gaining well above the range raises the risk of gestational diabetes, high blood pressure and a large baby, while gaining too little is linked to low birth weight and prematurity. The IOM figures are population guidance, not a strict rule — your midwife or doctor may set a different goal for your situation.
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