Pregnancy Weight Gain Calculator
Find your healthy weight gain range based on your BMI and current week
How Much Weight Should You Gain in Pregnancy?
The Institute of Medicine guidelines — the gold standard used by doctors and midwives worldwide — recommend different weight gain ranges depending on your pre-pregnancy BMI. Underweight women need to gain more to support healthy fetal development. Overweight and obese women are advised to gain less, as excess weight gain increases risks of gestational diabetes, high blood pressure, and difficult delivery.
For a single baby, the ranges are: underweight (BMI under 18.5) — gain 28 to 40 lbs (12.7 to 18.1 kg). Normal weight (BMI 18.5 to 24.9) — gain 25 to 35 lbs (11.3 to 15.9 kg). Overweight (BMI 25 to 29.9) — gain 15 to 25 lbs (6.8 to 11.3 kg). Obese (BMI 30 or above) — gain 11 to 20 lbs (5 to 9.1 kg).
Weight Gain Across the Trimesters
Weight gain is not linear throughout pregnancy. In the first trimester most women gain only 1 to 5 lbs as the baby is still very small and some women lose weight due to morning sickness. The second and third trimesters see the majority of weight gain — roughly 1 lb per week for normal weight women — as the baby, placenta, amniotic fluid, and maternal fat stores all develop significantly.
What Makes Up Pregnancy Weight Gain?
At full term, the typical breakdown of a 30 lb weight gain for a normal BMI woman is approximately: baby 7 to 8 lbs, placenta 1.5 lbs, amniotic fluid 2 lbs, uterus growth 2 lbs, breast tissue 2 lbs, blood volume 4 lbs, fluid retention 4 lbs, and maternal fat stores 7 lbs. Most of this weight is lost in the weeks following delivery.
Pregnancy Weight Gain Calculator — Frequently Asked Questions
How much weight should I gain during pregnancy?
Recommended pregnancy weight gain depends on your pre-pregnancy BMI. According to Institute of Medicine guidelines: underweight (BMI below 18.5) should gain 28–40 lbs; healthy weight (18.5–24.9) should gain 25–35 lbs; overweight (25–29.9) should gain 15–25 lbs; obese (30+) should gain 11–20 lbs.
How much weight gain is normal in the first trimester?
During the first trimester, most women gain 1–4 lbs in total. Nausea and food aversions in early pregnancy can sometimes result in little to no gain. The majority of pregnancy weight gain occurs in the second and third trimesters.
What does pregnancy weight gain consist of?
Pregnancy weight gain includes the baby (7–8 lbs), placenta (1.5 lbs), amniotic fluid (2 lbs), uterus growth (2 lbs), breast tissue (2 lbs), increased blood volume (4 lbs), fluid retention (4 lbs) and maternal fat stores (7 lbs) — totalling around 25–35 lbs for a healthy weight woman.