Pregnancy Weight Gain Calculator
Calculate your recommended pregnancy weight gain by trimester based on pre-pregnancy BMI. Uses IOM/ACOG guidelines.
IOM Weight Gain Guidelines
Normal BMI (18.5-24.9)
11.5 to 16 kg total
Recommended total gain over pregnancy
Weekly rate (2nd/3rd tri)
0.35 to 0.5 kg/week
Steady gain after week 12
The Institute of Medicine (IOM) guidelines, endorsed by ACOG, base recommended weight gain on pre-pregnancy BMI. Underweight women should gain more; overweight and obese women should gain less.
Gain by Pre-Pregnancy BMI
Healthy Pregnancy Tips
- ✓Focus on nutrient density, not eating for two
- ✓Aim for 300 extra kcal/day in 2nd trimester
- ✓Limit caffeine to 200mg/day
- ✓Take folic acid and vitamin D supplements
- ✓Stay active with 150 min moderate exercise/week
Formula, sources and limitations
How this estimate is produced
Sources
- Weight Gain During Pregnancy: Reexamining the Guidelines
National Academies Press, 2009
- Antenatal care (NG201)
NICE
Important limitations
- Population ranges do not account for multiple pregnancy, fetal growth, fluid changes, or medical conditions.
- The cited US guidance is not a personalised UK care recommendation.
A citation describes the source method; it does not mean this website or its implementation has been clinically validated or independently reviewed. See the methodology, editorial policy, and medical disclaimer.
Why Pregnancy Weight Gain Matters
Gaining within the recommended range reduces risk of gestational diabetes, pre-eclampsia, caesarean delivery, and macrosomia (large baby). Too little gain increases risk of preterm birth and low birth weight. These guidelines are population-level recommendations and individual needs may vary.
Nutrition During Pregnancy
Calorie needs increase by approximately 300 kcal/day in the 2nd trimester and 450 kcal/day in the 3rd trimester. Protein needs increase to 1.1g/kg/day. Key nutrients include folic acid, iron, calcium, vitamin D, omega-3 fatty acids, and iodine.