Enter your pre-pregnancy weight and height, then click Calculate
How Recommended Weight Gain Is Calculated
Your pre-pregnancy BMI is matched to an Institute of Medicine (IOM) weight gain category, each with its own total recommended gain range and expected weekly pace for the second and third trimesters. The first trimester target is small and roughly the same across categories, since most gain happens later in pregnancy.
Recommended Weight Gain by BMI (Singleton Pregnancy)
| Pre-Pregnancy BMI | Category | Total Recommended Gain | 2nd/3rd Tri Weekly Rate |
|---|---|---|---|
| Below 18.5 | Underweight | 28-40 lb (12.5-18 kg) | ~1.0 lb/wk (1.0-1.3) |
| 18.5-24.9 | Normal weight | 25-35 lb (11.5-16 kg) | ~1.0 lb/wk (0.8-1.0) |
| 25.0-29.9 | Overweight | 15-25 lb (7-11.5 kg) | ~0.6 lb/wk (0.5-0.7) |
| 30.0 and above | Obese | 11-20 lb (5-9 kg) | ~0.5 lb/wk (0.4-0.6) |
Source: Institute of Medicine, "Weight Gain During Pregnancy: Reexamining the Guidelines" (2009), the standard reference used by ACOG and most U.S. prenatal providers.
Recommended Weight Gain With Twins
| Pre-Pregnancy BMI | Category | Total Recommended Gain |
|---|---|---|
| Below 18.5 | Underweight | Insufficient data — consult your provider |
| 18.5-24.9 | Normal weight | 37-54 lb (16.8-24.5 kg) |
| 25.0-29.9 | Overweight | 31-50 lb (14.1-22.7 kg) |
| 30.0 and above | Obese | 25-42 lb (11.3-19.1 kg) |
The IOM has not published an official weekly gain rate for twin pregnancies, only total ranges. This calculator estimates a weekly pace by spreading the remaining gain evenly across the second and third trimesters — treat it as a general guide, and confirm specifics with your provider.
What If I'm Gaining Weight Faster or Slower Than Recommended?
Weight gain during pregnancy is rarely perfectly linear — it's normal to have some weeks or months that run a bit ahead of or behind the average pace. A single week outside the target range usually isn't cause for concern on its own. What matters more is the overall pattern over time, which is exactly what your prenatal visits are designed to track. If your gain is consistently running well above or below the recommended range, bring it up with your provider — they can look at your full history, your baby's growth, and any other individual factors before suggesting any changes, rather than reacting to one data point in isolation.
How Accurate Are These Recommendations?
These ranges reflect general population guidelines from the Institute of Medicine, intended to apply broadly across healthy pregnancies. They aren't personalized medical advice, and your own healthy target can differ based on factors like carrying multiples, a pre-existing health condition, your gain pattern in a previous pregnancy, or your provider's individualized assessment. Use this calculator as a starting point for a conversation with your prenatal care provider, not as a replacement for their guidance.
Related Calculators
Scientific References
- Institute of Medicine and National Research Council. "Weight Gain During Pregnancy: Reexamining the Guidelines." National Academies Press, 2009.
- American College of Obstetricians and Gynecologists (ACOG). "Weight Gain During Pregnancy." Committee Opinion No. 548, 2013 (reaffirmed).
- Centers for Disease Control and Prevention (CDC). "Weight Gain During Pregnancy" — Pregnancy and Nutrition guidance.
- American College of Obstetricians and Gynecologists (ACOG). "Obesity and Pregnancy." FAQ series.