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Pregnancy Weight Gain Calculator

Find the recommended total pregnancy weight gain for your pre-pregnancy BMI, for one baby or twins, and see how your gain so far compares.

Results

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Ranges are from the Institute of Medicine (2009), as published by the CDC, except underweight with twins, which the CDC lists separately. Most gain happens in the second and third trimesters. Your doctor or midwife may set a different goal for you.

Quick Answer

Recommended pregnancy weight gain depends on your BMI before pregnancy. With one baby, the Institute of Medicine suggests 25 to 35 lb for a normal BMI of 18.5 to 24.9, and 11 to 20 lb for a BMI of 30 or more. A woman who is 5 ft 5 in and weighed 140 lb has a BMI of 23.3, so her range is 25 to 35 lb.

Last updated: 2 November 2026 ·How we calculate this: the Institute of Medicine weight gain guidelines

Table of Contents

How This Pregnancy Weight Gain Calculator Works

Enter your weight before pregnancy and your height. The calculator works out your pre-pregnancy BMI, finds your BMI group, and shows the recommended total weight gain for one baby or twins. Add your current weight to see how much you have gained and how much is left to reach the range.

Quick explanation: people who start at a lower BMI are advised to gain more, and those at a higher BMI less.

  • Underweight: 28 to 40 lb.
  • Normal weight: 25 to 35 lb.
  • Overweight and obese: 15 to 25 lb and 11 to 20 lb.

How to Use the Pregnancy Weight Gain Calculator

  1. Choose US or metric units.
  2. Enter your weight before pregnancy and your height.
  3. Choose one baby or twins.
  4. Optionally, enter your current weight.
  5. Press Calculate to see your recommended range and progress.

Core Formulas

  • BMI: weight (kg) ÷ height (m)², or 703 × weight (lb) ÷ height (in)²
  • Target at delivery: pre-pregnancy weight + recommended gain
  • Gain so far: current weight − pre-pregnancy weight

Key Terms

  • BMI: body mass index, weight divided by height squared.
  • Pre-pregnancy weight: your weight just before you became pregnant.
  • Institute of Medicine (IOM): now the National Academy of Medicine, which set the 2009 guidelines.
  • Trimester: one of three stages of pregnancy.
  • Gestational weight gain: the weight gained during pregnancy.

Worked Example

You were 5 ft 5 in and 140 lb before pregnancy, and you are expecting one baby.

  • BMI = 703 × 140 ÷ 65² = 23.3, which is normal weight
  • Recommended gain = 25 to 35 lb
  • Target weight at delivery = 165 to 175 lb

Real-Life Examples

  • Starting with a low BMI: 5 ft 6 in and 110 lb is a BMI of 17.8, so the range is 28 to 40 lb.
  • Higher starting BMI: 5 ft 4 in and 190 lb is a BMI of 32.6, with a range of 11 to 20 lb.
  • Twins: with a normal BMI, the range rises to 37 to 54 lb.
  • Checking progress: enter your weight at each visit to see how you are tracking against the total.

Weight Gain vs Extra Calories

  • First trimester: the CDC says no extra calories are generally needed.
  • Second trimester: about 340 extra calories a day.
  • Third trimester: about 450 extra calories a day.
  • Twins: needs are higher, so ask your provider.

Recommended Gain by BMI

For triplets or more, ask your health care provider.

Pre-pregnancy BMIOne babyTwins
Under 18.5 (underweight)28 to 40 lb50 to 62 lb
18.5 to 24.9 (normal)25 to 35 lb37 to 54 lb
25.0 to 29.9 (overweight)15 to 25 lb31 to 50 lb
30.0 and over (obese)11 to 20 lb25 to 42 lb

Common Mistakes to Avoid

  • Using your current weight for BMI. The range is based on weight before pregnancy.
  • Eating for two. Extra calorie needs are modest, and none in the first trimester.
  • Dieting to lose weight. Weight loss is generally not advised in pregnancy without medical advice.
  • Comparing week to week too closely. Weight changes day to day with fluids.
  • Ignoring sudden gain. Rapid swelling or gain can be a warning sign, so call your provider.

Frequently Asked Questions

It depends on your BMI before pregnancy: 28 to 40 lb if underweight, 25 to 35 lb if normal, 15 to 25 lb if overweight and 11 to 20 lb if obese, for one baby.

37 to 54 lb with a normal BMI, 31 to 50 lb if overweight and 25 to 42 lb if obese. The CDC lists 50 to 62 lb for underweight.

Most gain happens in the second and third trimesters.

The CDC says generally none in the first trimester, about 340 a day in the second and about 450 a day in the third.

Talk to your provider. They may suggest changes to diet and activity.

Your provider can check your diet and the baby’s growth.

Before pregnancy.

For most people, yes. The CDC suggests working up to 150 minutes a week of moderate activity, with your provider’s advice.

A study cited by the CDC found only about 1 in 3 women gained the recommended amount.

To the baby, placenta, amniotic fluid, extra blood and fluid, breast tissue and some fat stores.

No. Ask your provider for a goal with triplets or more.

No. Your doctor or midwife may set a different goal for you.

References & Sources

SourceUsed ForLink
CDC, Weight Gain During Pregnancy Recommended ranges for one baby and twins, and extra calories. https://www.cdc.gov/maternal-infant-health/pregnancy-weight/index.html
ACOG Committee Opinion 700, Methods for Estimating the Due Date Pregnancy dating basics. https://www.acog.org/clinical/guidance/committee-opinion/2017/05/methods-for-estimating-the-due-date