How much weight should I gain during pregnancy?

IOM guidelines: Underweight (BMI <18.5): 28–40 lbs. Normal weight (18.5–24.9): 25–35 lbs. Overweight (25–29.9): 15–25 lbs. Obese (BMI ≥30): 11–20 lbs. These ranges support healthy outcomes for both mother and baby.

How much weight gain is normal in each trimester?

First trimester: 1–4 lbs total (nausea often limits gain). Second trimester: about 1 lb per week. Third trimester: about 1 lb per week, with gain slowing near the end. Most weight is gained in the second and third trimesters.

What happens if I gain too much weight during pregnancy?

Excessive gestational weight gain increases risk of gestational diabetes, C-section, high birth weight (macrosomia), and difficulty losing weight postpartum. Consult your healthcare provider if you are concerned about your weight gain trajectory.

Pregnancy Weight Gain Calculator - IOM Guidelines

BMI Category	BMI Range	Total Gain	1st Trimester	2nd/3rd Trimester Rate
Underweight	BMI < 18.5	28–40 lbs	1–4 lbs	~1 lb/week
Normal Weight	BMI 18.5–24.9	25–35 lbs	2–4 lbs	~1 lb/week
Overweight	BMI 25–29.9	15–25 lbs	2–4 lbs	~0.6 lb/week
Obese	BMI ≥ 30	11–20 lbs	1–2 lbs	~0.5 lb/week

BMI Category

BMI Range

Total Gain

1st Trimester

2nd/3rd Trimester Rate

Underweight

BMI < 18.5

28–40 lbs

1–4 lbs

~1 lb/week

Normal Weight

BMI 18.5–24.9

25–35 lbs

2–4 lbs

~1 lb/week

Overweight

BMI 25–29.9

15–25 lbs

2–4 lbs

~0.6 lb/week

Obese

BMI ≥ 30

11–20 lbs

1–2 lbs

~0.5 lb/week

About Pregnancy Weight Gain

The Institute of Medicine (IOM) guidelines for gestational weight gain are based on pre-pregnancy BMI and are designed to optimize outcomes for both mother and baby. Women who gain within the recommended range tend to have lower rates of gestational diabetes, cesarean delivery, preterm birth, and postpartum weight retention. Pre-pregnancy BMI is the key factor determining the recommended range — which is why this calculator first computes your BMI before showing your personalized guidance. For tracking your overall pregnancy timeline, visit our Pregnancy Calculator.

Weight gain during pregnancy is not linear. Most women gain very little in the first trimester (1–4 lbs for normal weight women), then gain more steadily in the second and third trimesters. The IOM recommends approximately 1 lb per week for normal-weight women during the second and third trimesters, with lower rates for overweight (0.6 lb/week) and obese women (0.5 lb/week). Being "on track" does not mean hitting a precise number each week — weight can fluctuate from day to day. The trend over several weeks is what matters most.

Women carrying twins or multiples have different weight gain recommendations — typically 37–54 lbs for normal-weight women with twins — and should always consult their obstetric team for personalized guidance. It is also important to remember that weight gain alone does not capture the full picture of pregnancy health; blood pressure, blood sugar, fetal growth, and other factors are equally important. To estimate your due date or check pregnancy milestones, see our Due Date Calculator.

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For a related calculation, use Ovulation Calculator to calculate ovulation date, fertile window, and next expected period from your cycle length. Alternatively, use Due Date Calculator to calculate your due date from LMP, conception date, or IVF transfer date with gestational age.

Pregnancy Weight Gain Calculator

About Pregnancy Weight Gain

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