How much weight should you gain in pregnancy?
About this calculator
How much weight should you gain in pregnancy? It depends on your pre-pregnancy BMI, not a single number for everyone. The Institute of Medicine (IOM) guidelines used by obstetricians worldwide set different total gain ranges for underweight, normal, overweight, and obese mothers-to-be.
Enter your pre-pregnancy weight, height, and current gestational week. The calculator computes your pre-pregnancy BMI, assigns an IOM category, and shows how much gain is typical by this point in pregnancy. It also gives your full-pregnancy target (for example, 11.5–16 kg if you started at a normal BMI) and the recommended weekly rate after week 13.
First trimester gain is usually modest — about 0.5–2 kg total. Most gain happens in the second and third trimesters. Weigh yourself once a week on the same scale, at the same time of day. Sudden swelling, rapid gain, or loss needs a call to your doctor.
Pair this with the [[pregnancy]] calculator for due date and week tracking, the [[bmi]] calculator for pre-pregnancy BMI context, and the [[calorie]] or [[tdee]] calculator for trimester calorie needs. The [[ideal-weight]] calculator helps set postpartum targets.
Common uses
- Checking if 8 kg gained at week 24 fits IOM guidance for a normal-BMI pregnancy
- Planning weight goals after starting pregnancy overweight at BMI 28
- Understanding weekly gain targets in the third trimester
- Comparing twin vs singleton guidance with your obstetrician (this tool uses singleton IOM ranges)
- Tracking gain after IVF or late first-trimester confirmation when LMP dating differs
Frequently asked questions
How much weight should I gain if my pre-pregnancy BMI is 22?
A normal BMI (18.5–24.9) maps to 11.5–16 kg total gain. First trimester: about 0.5–2 kg. After week 13, aim for roughly 0.42 kg per week through delivery if you stay on track.
What if I gain more than the IOM range?
One high week is not a crisis. Patterns over several weeks matter more. Talk to your obstetrician before restricting calories — pregnancy needs steady nutrition for fetal growth and your health.
Do I need to gain less if I am overweight before pregnancy?
Yes. Overweight (BMI 25–29.9) targets 7–11.5 kg total; obese (BMI 30+) targets 5–9 kg. You still need to gain — zero gain is not recommended — but the range is lower to reduce gestational diabetes and hypertension risk.
How is gestational week different from months pregnant?
Doctors count pregnancy from the first day of your last period (LMP), so week 1 starts before conception. Month 5 is roughly weeks 18–22. Use the same week count your clinic uses for consistency.
Does this calculator replace my doctor's advice?
No. IOM ranges are population guidelines. Your doctor may adjust targets for twins, short stature, prior preterm birth, or medical conditions. Always follow your obstetrician