Pregnancy weight gain calculator

The calculator uses the 2009 Institute of Medicine (IOM, now the National Academy of Medicine) guidelines for a single pregnancy, which ACOG and the CDC also use:

Your pre-pregnancy BMI is calculated from your height and the weight you entered.

In the first trimester, total gain is typically small, about 1.1–4.4 lb (0.5–2 kg). After week 13, the calculator spreads the rest of the recommended total evenly up to week 40. That gives a simple target range for any week.

Example: pre-pregnancy 5 ft 5 in and 135 lb gives a BMI of 22.5 (normal weight). The recommended total is 25–35 lb. At week 24, the suggested range is about 11–17 lb. If you now weigh 148 lb, you've gained 13 lb, which is within the range.

Real weight gain isn't perfectly linear; this is an approximation meant to show whether you're roughly on track.

At full term, a typical gain of around 30 lb is made up of several parts: the baby (about 7–8 lb), the placenta, amniotic fluid, larger uterus and breast tissue, increased blood and fluid volume, and some fat stores for breastfeeding. Only part of the gain is fat, which is why weight usually drops noticeably right after birth.

A single reading outside the range isn't a cause for alarm. Weight shifts with fluids, meals and time of day. Look at the trend over several weeks and discuss it with your OB-GYN or midwife, who will consider your overall health and your baby's growth.

Gaining much more than recommended is linked to a higher risk of gestational diabetes, high blood pressure and a larger baby; gaining too little is linked to lower birth weight. Your provider can help you adjust your diet and activity safely. Pregnancy isn't the time for a weight-loss diet unless your provider advises it.

These ranges apply to a single baby. For twins, the IOM provisional guidelines are higher (for example, 37–54 lb for normal-weight women). If you're pregnant with multiples, have a medical condition or started pregnancy at a very low or very high weight, your provider will give you a personal target.

You can switch between pounds and kilograms with the unit toggle. This calculator is informational only and isn't medical advice. Everything is calculated in your browser, so your information stays private.