Pregnancy Weight Gain Calculator
By Santaji GadepatilinUpdated October 27, 2026
Recommended weight gain in pregnancy depends on your BMI before pregnancy. Staying in range supports a healthy pregnancy. This free pregnancy weight gain calculator solves for whichever value you leave blank and shows the formula and steps.
How to use the pregnancy weight gain calculator
Enter your weight before pregnancy and your height. The calculator works out your pre-pregnancy BMI and the recommended total weight gain range for a single baby.
This is general guidance. Your doctor or midwife may recommend a different target based on your health.
IOM 2009 recommendations (single baby)
| Pre-pregnancy BMI | Total gain | Weekly gain, 2nd and 3rd trimesters |
|---|---|---|
| Underweight (under 18.5) | 12.5–18 kg (28–40 lb) | about 0.5 kg (1–1.3 lb) |
| Healthy (18.5–24.9) | 11.5–16 kg (25–35 lb) | about 0.4 kg (0.8–1 lb) |
| Overweight (25–29.9) | 7–11.5 kg (15–25 lb) | about 0.3 kg (0.5–0.7 lb) |
| Obese (30+) | 5–9 kg (11–20 lb) | about 0.2 kg (0.4–0.6 lb) |
Source: Institute of Medicine (now National Academy of Medicine), Weight Gain During Pregnancy, 2009.
Where the weight goes
For a typical healthy pregnancy of about 13 kg:
| Component | Approximate weight |
|---|---|
| Baby | 3.4 kg |
| Placenta | 0.7 kg |
| Amniotic fluid | 0.8 kg |
| Uterus | 0.9 kg |
| Breast tissue | 0.4 kg |
| Blood volume | 1.4 kg |
| Fluid in tissues | 1.5 kg |
| Fat stores | 3–4 kg |
Healthy habits
- Eat regular balanced meals; most people need only about 300–450 extra kcal a day in the second and third trimesters, and none in the first.
- Stay active with approved exercise such as walking or swimming.
- Take supplements such as folic acid and iron as advised.
Asian BMI cut-offs
Some guidelines suggest lower BMI cut-offs for Asian women, which would shift some people into a higher category. Ask your care provider which cut-offs they use.
Frequently asked questions
How much weight should I gain during pregnancy?
It depends on your BMI before pregnancy. For a healthy BMI (18.5–24.9), the IOM recommends 11.5–16 kg (25–35 lb) for a single baby.
How much weight should I gain with twins?
For twins, IOM provisional ranges are 17–25 kg (37–54 lb) for healthy BMI, 14–23 kg for overweight and 11–19 kg for obese.
How fast should I gain weight?
Typically 0.5–2 kg in the first trimester, then about 0.4 kg a week (1 lb) in the second and third trimesters for a healthy BMI.
Is it safe to lose weight during pregnancy?
Weight loss is not generally recommended in pregnancy. Speak to your doctor or midwife about any weight concerns.