Find your recommended weight gain during pregnancy based on your pre-pregnancy BMI, using Institute of Medicine guidelines — a healthy range for you and your baby.
cm
kg
ft
in
lb
Recommended total gain
11.5–16 kg
Pre-pregnancy BMI 22.0 · Normal
Guidelines by pre-pregnancy BMI
Category (BMI)
Gain (kg)
Gain (lb)
Underweight (<18.5)
12.5–18
28–40
Normal (18.5–24.9)
11.5–16
25–35
Overweight (25–29.9)
7–11.5
15–25
Obese (30+)
5–9
11–20
How to use the pregnancy weight gain calculator
Enter your height and your weight before pregnancy. The calculator works out your pre-pregnancy BMI, places you in a category, and shows the total weight gain recommended for a healthy single pregnancy. Use it as a guide and let your midwife or doctor tailor it to you.
Where the weight goes
Only a few kilograms of pregnancy weight is the baby itself — the rest is the placenta, extra blood and fluid, a larger uterus and breasts, and some fat stores for breastfeeding. Gaining within the recommended range supports your baby's growth while keeping risks low and making it easier to return to your pre-pregnancy weight afterwards.
Frequently asked questions
It depends on your pre-pregnancy BMI. Using Institute of Medicine guidelines, a woman of normal weight should gain about 11.5–16 kg (25–35 lb) over the pregnancy; underweight women a little more, and overweight or obese women less. The calculator gives your range from your height and pre-pregnancy weight.
Starting weight affects how much extra is healthy for you and your baby. Women who begin underweight benefit from gaining more, while those who begin with a higher BMI are advised to gain less to reduce risks like gestational diabetes and high blood pressure.
Most women gain little in the first trimester (around 0.5–2 kg total), then roughly 0.4–0.5 kg a week in the second and third trimesters if they started at a normal weight. The total, not the week-by-week figure, is what the guidelines target.
Recommended gain is higher for multiples — for twins, normal-weight women are often advised to gain around 17–25 kg. This calculator covers single pregnancies; ask your doctor for guidance if you are expecting more than one baby.
Gaining well above or below the guideline range can raise risks for you and your baby, but everyone is different. Use this as a general guide and let your midwife or doctor advise you based on your individual pregnancy.