Pregnancy Weight Gain Calculator: How Much Should You Gain, Week by Week?

Weight gain is one of the most-checked numbers in pregnancy, and one of the most worried about. The guidelines used in the US come from the Institute of Medicine (now the National Academy of Medicine), published in 2009, and the CDC and ACOG both follow them. They're ranges, not targets, and they're based on one thing: your body mass index (BMI) before pregnancy.

The Recommended Ranges

In the first trimester, ACOG says you may gain only 1 to 5 pounds, or nothing at all, and some people lose a little because of nausea. Most of the gain happens from week 14 onward, which is why the calculator's range climbs slowly at first and faster later.

If You're Expecting Twins

The ranges for twins are higher. These are the figures the CDC lists:

• Underweight: 50 to 62 pounds
• Healthy weight: 37 to 54 pounds
• Overweight: 31 to 50 pounds
• Obesity: 25 to 42 pounds

The underweight twin range is the CDC's own figure, because the Institute of Medicine didn't set one. For triplets or more, there's no standard range, so your provider will set a goal with you. Tick the twins box in the calculator to see the twin range for your BMI.

Why the Range Matters

The CDC calls pregnancy weight gain important both for your pregnancy and for the long-term health of you and your baby. In the research behind the guidelines, gaining well above the range was linked to a larger baby, a higher chance of a cesarean birth and keeping extra weight after birth, while gaining well below it was linked to a baby born small or early. It's also very common to be outside the range: the CDC cites a study in which only about 1 in 3 women gained the recommended amount, 1 in 5 gained less and 1 in 2 gained more.

Those are risks across large groups of people, not predictions for you. A week or two outside the range is common and usually means nothing. What your provider looks at is the overall pattern across your appointments.

How to Read Your Result

• Within the range: keep doing what you're doing.
• A little under: very common in the first trimester and with nausea. If it continues into the second trimester, your provider may suggest adding a snack or two with protein.
• A little over: also common, and fluid retention can add several pounds quickly, especially late in pregnancy. Sudden swelling of the face or hands, or a rapid jump in weight, is worth a call to your provider, because it can be a sign of preeclampsia.

Whatever the number says, pregnancy is not the time to diet. If you're gaining faster than expected, the usual advice is to look at what you're eating rather than how much, swapping sugary drinks and snacks for foods with protein and fiber, and keeping active in ways your provider has okayed.

How Many Calories Is That?

Gaining within the range doesn't take much extra food. The extra energy pregnancy needs is roughly nothing in the first trimester, about 340 calories a day in the second and about 450 in the third. Our pregnancy calorie calculator works out your daily number, and our pregnancy macro calculator splits it into protein, carbs and fat.

If you'd like to see how your meals add up day to day, our guide to pregnancy nutrition apps explains what to look for in one built for pregnancy, rather than for weight loss.

A Note on BMI

BMI is a rough measure. It doesn't know how much of your weight is muscle, and it can sit awkwardly for very tall or very short people, or for different body types. The guidelines use it because it's simple and was the basis for the research, but your provider can take your whole history into account. If your result doesn't feel right for you, that's a good conversation to have at your next appointment.

This calculator gives general ranges from published guidelines. It isn't medical advice, and your provider may recommend a different target based on your health and history.