Pregnancy Weight Gain Calculator
Quick answer
Work out your pre-pregnancy BMI from your height and weight, then see the total weight-gain range recommended by the Institute of Medicine (IOM 2009) for your BMI category — plus how much to gain per week in the second and third trimesters.
Last updated:
Your details
Everything runs in your browser — nothing is stored or sent anywhere.
How the ranges are set
BMI = pre-pregnancy weight (kg) ÷ height (m²)
Total gain: underweight 12.5–18 kg, normal 11.5–16 kg
Overweight 7–11.5 kg, obese 5–9 kg
2nd / 3rd trimester weekly rates: 0.5 / 0.4 / 0.3 / 0.2 kg
These are the IOM 2009 guidelines for a singleton pregnancy in healthy women. Twin or triplet pregnancies and individual health conditions need different, personal targets.
Worked example
- 1
A woman is 165 cm (1.65 m) tall and weighed 54 kg before pregnancy.
- 2
BMI = 54 ÷ (1.65 × 1.65) = 54 ÷ 2.7225 ≈ 19.8 — normal weight.
- 3
IOM total range → 11.5–16 kg (25–35 lb).
- 4
2nd / 3rd trimester → about 0.4 kg (1 lb) per week.
IOM 2009 weight-gain ranges
| Your result | Category | What it means |
|---|---|---|
| BMI under 18.5 | Underweight | Aim for 12.5–18 kg (28–40 lb) total gain — about 0.5 kg (1 lb) per week in the second and third trimesters. |
| BMI 18.5 – 24.9 | Normal weight | Aim for 11.5–16 kg (25–35 lb) total gain — about 0.4 kg (1 lb) per week in the second and third trimesters. |
| BMI 25.0 – 29.9 | Overweight | Aim for 7–11.5 kg (15–25 lb) total gain — about 0.3 kg (0.6 lb) per week in the second and third trimesters. |
| BMI 30 or above | Obese | Aim for 5–9 kg (11–20 lb) total gain — about 0.2 kg (0.5 lb) per week in the second and third trimesters. |
Institute of Medicine (2009) guidelines for healthy women with a singleton pregnancy, based on pre-pregnancy BMI.
Frequently asked questions
Sources & further reading
Related calculators
Due Date Calculator
Estimate your pregnancy due date (Naegele’s rule).
Open calculatorOvulation Calculator
Predict ovulation day and your fertile window.
Open calculatorBMI Calculator
Body Mass Index with healthy weight range and daily calories.
Open calculatorPregnancy Calorie Calculator
Daily calorie needs by trimester
Open calculatorPregnancy Weeks Calculator
How many weeks and days — and what is left.
Open calculatorBreastfeeding Calorie Calculator
Extra daily calories while breastfeeding.
Open calculatorPostpartum Recovery Timeline
A realistic, general timeline of physical recovery milestones
Open calculatorThis calculator provides general estimates for informational purposes only and is not medical advice. For personal guidance, consult a qualified healthcare provider.