BumpTrack

Pregnancy Weight Gain Calculator

Are you gaining at the right pace? Compare your pregnancy weight gain to IOM guidelines.

Pre-pregnancy weight (lbs)

Height (inches)

Current week

Recommended gain by week 20

9.1–12.5 lbs

BMI: 23.3 (Normal weight)

Pre-pregnancy BMI: 23.3 (Normal weight)
Recommended total gain: 25–35 lbs

What you entered

Weight: 140 lbsHeight: 65 inWeek: 20

1
Pre-pregnancy BMI
(140 ÷ 65²) × 703= 23.3 (Normal weight)
2
Recommended total gain
Normal weight BMI range= 25–35 lbs
3
Recommended gain by week 20
1st tri base + weekly rate × weeks= 9.1–12.5 lbs

Result

Recommended gain: 9.1–12.5 lbs

With a pre-pregnancy BMI of 23.3 (Normal weight), the IOM recommends gaining 25–35 lbs total. By week 20, you should have gained approximately 9.1–12.5 lbs.

Recommended pregnancy weight gain by pre-pregnancy BMI

Institute of Medicine guidance sets a total gain range based on BMI before pregnancy, then spreads it across the pregnancy.

Pre-pregnancy weight	Height	BMI	Category	Recommended total	Expected by week 20
110 lb	5 ft 5 in	18.3	Underweight	28 - 40 lb	11.0 - 15.1 lb
130 lb	5 ft 5 in	21.6	Normal weight	25 - 35 lb	9.1 - 12.5 lb
160 lb	5 ft 5 in	26.6	Overweight	15 - 25 lb	5.5 - 8.9 lb
190 lb	5 ft 5 in	31.6	Obese	11 - 20 lb	4.3 - 7.7 lb

Gain is slow in the first trimester and steadier afterwards, so the week 20 figure is well under half the total. Ranges are for single pregnancies; twins carry higher targets. General wellness information only, not medical advice. Discuss any health decision with a qualified clinician.

IOM weight gain guidelines by BMI

The Institute of Medicine recommends total pregnancy weight gain of 28-40 lbs for underweight women (BMI < 18.5), 25-35 lbs for normal weight (18.5-24.9), 15-25 lbs for overweight (25-29.9), and 11-20 lbs for obese (≥ 30). Most gain occurs in the 2nd and 3rd trimesters.

Where pregnancy weight goes

Of 30 lbs total gain, roughly: baby 7.5 lbs, placenta 1.5 lbs, amniotic fluid 2 lbs, uterine growth 2 lbs, breast tissue 2 lbs, blood volume 4 lbs, fluid 4 lbs, fat/nutrient stores 7 lbs. Gaining too little increases risk of preterm birth; gaining too much increases risk of gestational diabetes and C-section.

Frequently asked questions

How much weight should I gain during pregnancy?

IOM guidelines by pre-pregnancy BMI: Underweight (BMI < 18.5): 28–40 lbs total. Normal weight (18.5–24.9): 25–35 lbs. Overweight (25–29.9): 15–25 lbs. Obese (≥ 30): 11–20 lbs. For twins, add about 10–15 lbs to each range. Most gain happens in the 2nd and 3rd trimesters at about 1 lb/week.

When does most pregnancy weight gain happen?

First trimester: 2–5 lbs total (some women lose weight due to morning sickness). Second trimester: about 1 lb/week. Third trimester: about 1 lb/week, slowing near the end. A sudden gain of 5+ lbs in a week could indicate preeclampsia — contact your provider.

Is it harmful to gain too much weight during pregnancy?

Excess weight gain increases risk of gestational diabetes, preeclampsia, C-section, large-for-gestational-age baby, and difficulty losing weight postpartum. Gaining too little increases risk of preterm birth and small baby. Staying within the recommended range for your BMI category gives the best outcomes for both mother and baby.