Pregnancy Weight Gain Calculator

Use your weight from before you were pregnant. Your BMI will go up as your pregnancy goes on, and that is normal, so a BMI worked out from your weight today does not tell you which range applies. If you do not know your weight before pregnancy, use the first weight measured in early pregnancy, for example at your first appointment, and treat the result as approximate.

For twins, the guidelines give these totals: 37 to 54 lb (16.8 to 24.5 kg) at a healthy weight, 31 to 50 lb (14.1 to 22.7 kg) if overweight, and 25 to 42 lb (11.3 to 19.1 kg) if obese. These ranges are provisional. For underweight women with twins the CDC lists 50 to 62 lb (22.7 to 28.1 kg), but that figure is not from the Institute of Medicine. Week-by-week targets for twins are not well established, so this calculator shows the total only. Your provider can set a goal that fits your pregnancy.

In the first trimester most people gain little, about 1.1 to 4.4 lb (0.5 to 2 kg) in total. After that the guidelines expect a steady gain each week: roughly 1 to 1.3 lb (0.44 to 0.58 kg) if underweight, 0.8 to 1 lb (0.35 to 0.5 kg) at a healthy weight, 0.5 to 0.7 lb (0.23 to 0.33 kg) if overweight, and 0.4 to 0.6 lb (0.17 to 0.27 kg) if obese. The week-by-week table on this page is an estimate built from those figures. Real pregnancies are not perfectly steady.

UK guidance does not set weight gain targets. NICE says there are no evidence-based UK guidelines on recommended weight gain ranges, and the RCOG says there is no agreement on the best amount. Your weight and BMI are measured at your booking appointment. After that, practice varies: some units only weigh you again if there is a reason, while some NHS trusts use the US ranges and weigh at each visit. The ranges on this page are the US ones, so treat them as a general guide and follow your midwife's advice.

They come from the 2009 Institute of Medicine guidelines, which the CDC uses. They were developed in the United States and use standard BMI categories. Some countries publish their own ranges, and some, like the UK, do not set targets. The CDC reports that only about 1 in 3 women gain within the recommended range, so being outside it is common. If your provider gives you a different goal, follow your provider's advice.

Small changes, including a little weight loss, are common in the first trimester, especially with nausea. The guide here counts from your weight before pregnancy. Tell your midwife or doctor if you cannot keep food or drink down, or if you keep losing weight.

One reading is not a trend. Scales vary with fluid, time of day and clothes, and babies grow at different rates, so being a little above or below the guide is common. Do not cut back on food by yourself. Bring it up with your midwife or doctor, who can look at the whole picture, including your blood pressure and your baby's growth. If weighing is stressful, you can leave the current weight box empty and just use the range.

Trying to lose weight on purpose during pregnancy is not recommended, even if you started pregnancy above a healthy weight. NICE advises against dieting in pregnancy because it may harm the baby. If you are overweight or obese, the guidelines already suggest a lower total gain, and your provider can help you aim for it safely. Some people lose a little weight naturally, for example from nausea. Mention that to your provider rather than treating it as a goal.

It works out your BMI from your weight before pregnancy and your height, finds your BMI group, and applies the Institute of Medicine range: a small gain in the first trimester, then a steady weekly gain to 40 weeks. It's a guide, not a diagnosis.