Pregnancy Weight Gain Calculator
Calculate recommended total weight gain and trimester-by-trimester targets based on your pre-pregnancy BMI and IOM 2009 guidelines. Results in kg and lbs. Enter height and weight in your preferred unit.
Pregnancy Weight Gain Calculator
IOM 2009 guidelines · kg or lbs → trimester targets
Always discuss weight gain with your obstetrician or midwife — individual recommendations may vary based on medical history and pregnancy complications.
Based on IOM (Institute of Medicine) 2009 weight gain recommendations during pregnancy, the current standard used by ACOG, NHS, and most global obstetric guidelines. Results shown in both kg and lbs.
Pregnancy Weight Gain Recommendations by BMI (IOM 2009)
| Pre-Pregnancy BMI | Category | Total Gain (kg) | Total Gain (lbs) | 2nd–3rd Trimester/week |
|---|---|---|---|---|
| Below 18.5 | Underweight | 12.5–18 kg | 28–40 lbs | 0.5–0.6 kg/week |
| 18.5–24.9 | Normal weight | 11.5–16 kg | 25–35 lbs | 0.4–0.5 kg/week |
| 25.0–29.9 | Overweight | 7–11.5 kg | 15–25 lbs | 0.2–0.3 kg/week |
| 30.0+ | Obese | 5–9 kg | 11–20 lbs | 0.2–0.3 kg/week |
| Any (twins) | Normal weight twins | 16.8–24.5 kg | 37–54 lbs | 0.6–0.7 kg/week |
Why Pregnancy Weight Gain Matters
Gaining the recommended amount of weight during pregnancy supports fetal development while minimising risks for both mother and baby. Too little weight gain — especially in underweight women — is associated with preterm birth, low birth weight, and impaired fetal neurodevelopment. Too much weight gain increases risk of gestational diabetes, preeclampsia, caesarean delivery, macrosomia (large baby), and greater difficulty losing postpartum weight. Both extremes increase long-term health risks for the child, including metabolic disease in adulthood. The IOM ranges balance these competing concerns based on extensive epidemiological data.