Pregnancy weight gain calculator
Enter your height and weight before pregnancy, get the recommended gain.
How much weight should I gain during pregnancy?
It depends on your BMI before pregnancy. The Institute of Medicine (2009) recommends 28–40 lb if underweight, 25–35 lb at a normal weight, 15–25 lb if overweight and 11–20 lb with obesity, for one baby.
What about twins?
Provisional IOM ranges: 37–54 lb at a normal weight, 31–50 lb if overweight and 25–42 lb with obesity. The IOM had too little data to set a range for underweight women carrying twins.
How fast should I gain?
In the second and third trimesters, about 1 lb a week at normal weight (0.8–1), 1 lb (1–1.3) if underweight, 0.6 lb (0.5–0.7) if overweight and 0.5 lb (0.4–0.6) with obesity. The IOM assumes a gain of 1.1–4.4 lb in the first trimester.
Which BMI do I use?
Your BMI before pregnancy, from your pre-pregnancy weight and height. The calculator works it out.
What if I am outside the range?
Talk with your prenatal care provider — they set goals for your own situation.
Does the recommended range include the baby’s weight?
Yes. The ranges are for total weight gain, which includes the baby, placenta, amniotic fluid, larger breasts and uterus, blood and fluid volume, and body stores. It is measured on the scale against your weight before pregnancy.
How the range is chosen
The recommendation depends on your BMI before pregnancy, which is weight in pounds × 703 ÷ height in inches squared (or kilograms divided by meters squared). The cutoffs are 18.5, 25 and 30. For one baby, the 2009 Institute of Medicine range is 28–40 lb if underweight, 25–35 lb at normal weight, 15–25 lb if overweight and 11–20 lb with obesity. After the first trimester, the guide for weekly gain is about 1.0 lb a week if underweight, 1.0 lb at normal weight, 0.6 lb if overweight and 0.5 lb with obesity.
A worked example
A woman who is 5 ft 5 in (65 inches) and weighed 130 lb before pregnancy has a BMI of 703 × 130 ÷ 65² = 21.6, which is in the normal-weight band (18.5 to 24.9). The range for one baby is 25–35 lb, and from the second trimester about 0.8–1.0 lb a week is on track (1.0 lb a week on average). With twins at the same BMI the provisional range is 37–54 lb.
Common mistakes
Using today’s weight instead of the weight before pregnancy puts you in the wrong category, and the categories change the range by 10 or more pounds. Applying the weekly figure to the first trimester is another error, since the guidelines expect only a small gain then. A third is treating the range as a target to reach: it is a guide for health outcomes, and individual circumstances such as nausea, a multiple pregnancy or a medical condition change the right goal. Your own prenatal provider sets the plan.
Sources: Institute of Medicine and National Research Council, Weight Gain During Pregnancy: Reexamining the Guidelines (2009), Table S-1, as also published by the CDC; BMI categories from the CDC. Related: BMI calculator, pregnancy week calculator, due date calculator and calorie calculator.
For general information only — not medical advice. Talk with your doctor or another health professional about your own health. How we check our calculators.