Pregnancy Weight Gain Calculator

Pregnancy Weight Gain

The amount of weight you should expect to gain during your pregnancy depends on your pre-pregnancy BMI, and how far along you are in your pregnancy. According to the American College of Obstetrics and Gynecology (ACOG), for a normal BMI you should expect to gain 1–4 pounds in the first trimester, and about a pound a week during the second and third trimesters.

Across all BMI categories, first trimester total expected weight gain is around only 1–4 pounds. After this the recommended weight gain rate differs between the normal and overweight BMI categories. In the 2nd and 3rd trimesters people with an overweight starting BMI should expect to gain about 0.6 pounds per week, which is less than the normal BMI rate of about one pound per week.

The US National Academy of Medicine, along with ACOG, recommend a lower rate of gestational weight gain for overweight individuals. This is to help avoid weight-related health complications over the course of a pregnancy.

Calculating Pre-Pregnancy BMI

BMI is body mass index, calculated using your height and weight and the BMI formula. Your starting BMI category - underweight, normal, overweight, or obsese - sets your recommended weight gain across your pregnancy. The BMI formula using pounds and inches is:

BMI = weight ÷ height² × 703

Multiply your weight in pounds by your height squared in inches. Then multiply that result by 703 to get your BMI.

Gestational Week

How far along in pregnancy you are, combined with your starting BMI, lets us calculate your expected pregnancy weight gain up to your current gestational week. Of course this is not a pinpoint set amount of weight but rather a range of expected weight gain given your current week of pregnancy.

The calculator uses the American College of Obstetrics and Gynecology (ACOG) recommendations for healthy weight gain throughout a pregnancy.

• First trimester: 1–4 lbs total, regardless of BMI category
• Second and third trimesters: a weekly weight-gain expectation based on BMI category
  • Normal BMI: About 1 pound per week
  • Overweight BMI: About 0.6 pounds per week
  • Underweight and Obese BMI: Healthcare practitioners should advise pregnant individuals in these BMI categories about weight gain during pregnancy.

Pregnancy Weight Gain Calculation

The pregnancy weight gain calculator works like this:

1. Calculate pre-pregnancy BMI given your pre-pregnancy height and weight
2. Match the pre-pregnancy BMI to the recommended total weight gain range.¹
3. Assess total expected weight gain given gestational week. Add a total of 1-4 pounds for first trimester gain, and add the weekly gain rate multiplied by the number of weeks after the first trimester. The result is the expected weight gain to-date.
4. Compare this figure to actual weight gain to see if your pregnancy weight gain is in line with expected gain.

Recommended Pregnancy Weight Gain by BMI

Every pregnant person's body is unique, but there are optimal weight gain expectations during pregnancy. These recommended weight gain ranges are based on guidelines from ACOG and NAM.

Healthy Pregnancy Weight Gain by Trimester

First trimester, weeks 1–12: Most people gain about 1–4 lbs total. Nausea may cause temporary weight loss.

Second trimester, weeks 13–26: Steady gain of about 1 pound per week begins for people in a normal weight range.

Third trimester, weeks 27–40: The same rate of weight gain continues at roughly 1 pound per week. The baby gains half its birth weight during these final weeks.

Where the Pregnancy Weight Goes

For typical singleton (one-baby) pregnancy, total weight gain generally comes from:

• Baby: 7–8 lbs
• Placenta: 1–2 lbs
• Amniotic fluid: 2 lbs
• Uterus growth: 2 lbs
• Breast tissue: 2 lbs
• Increased blood volume: 3–4 lbs
• Extra fluid in body tissues: 3–4 lbs
• Fat stores (energy reserves for labor and breastfeeding): 6–8 lbs

Maintaining Healthy Weight Gain During Pregnancy

• Eating: Beginning in the second trimester you need about 300 extra calories per day. Health practitioners warn against increasing caloric intake beyond that, and recommend focusing those extra calories on protein, whole grains and healthy fats.
• Exercise: Walking, swimming and prenatal yoga are all safe and help manage weight gain without compromising nutrition. Many other forms of exercise are safe during pregnancy. Ask your healthcare provider what's right for you given your exercise preferences.
• Gaining too fast: Good decisions around nutrition apply to pregnant people as with non-pregnant people. It's generally recommended to limit processed foods and added sugars. Be sure to talk to your healthcare provider if you have questions or concerns. Remember that excess pregnancy weight gain raises the risk of gestational diabetes and delivery complications.
• Not gaining enough: Talk to your doctor. Low weight gain in the second and third trimesters can affect fetal growth.

Recommended Pregnancy Weight Gain by Week

The table below shows cumulative recommended weight gain ranges by pregnancy week given BMI range. Note that this table applies to singleton pregnancies and is based on the IOM 2009 guidelines published by ACOG. Values are in pounds (lbs).

Source

National Academy of Medicine (US) and National Research Council (US) Committee to Reexamine Pregnancy Weight Guidelines. Weight Gain During Pregnancy: Reexamining the Guidelines. Rasmussen KM, Yaktine AL, editors. Washington (DC): National Academies Press (US); 2009. As cited in ACOG Committee Opinion No. 548, Weight Gain During Pregnancy, January 2013 and Reaffirmed in 2026.

Notes

¹ Weight gain ranges are based on ACOG Weight Gain During Pregnancy developed from US National Academy of Medicine guidelines.