Pregnancy & Fertility
Pregnancy Weight Gain Calculator
Gaining the right amount matters for you and the baby. Get your total target and the weekly pace recommended by the IOM.
Recommended pregnancy weight gain depends on pre-pregnancy BMI: 12.5–18 kg for underweight, 11.5–16 kg for normal weight, 7–11.5 kg for overweight, and 5–9 kg for obesity, per the Institute of Medicine. Dates are estimates — confirm timing with your provider and ultrasound where relevant.
Targets set by pre-pregnancy BMI.
Normal BMI: 11.5–16 kg total.
2nd/3rd trimester: ~0.4 kg/week.
Calculate Your Pregnancy Weight Gain
Total Target Gain
What Is Pregnancy Weight Gain?
Weight gain supports fetal growth, placenta, fluids, and maternal reserves. The Institute of Medicine (IOM) sets targets by pre-pregnancy BMI, because both too little and too much gain carry risks.
Gain is back-loaded: little in the first trimester, then roughly 0.2–0.6 kg per week depending on BMI category.
How It Is Calculated
Target = f(pre-pregnancy BMI) per IOM 2009 guidelines
Example: Example: 65 kg, 165 cm (BMI 23.9) → total target 11.5–16 kg
IOM total gain targets
| Pre-pregnancy BMI | Total gain | Weekly rate (2nd/3rd trim.) |
|---|---|---|
| Underweight (<18.5) | 12.5–18 kg | 0.44–0.58 kg |
| Normal (18.5–24.9) | 11.5–16 kg | 0.35–0.50 kg |
| Overweight (25–29.9) | 7–11.5 kg | 0.23–0.33 kg |
| Obese (≥30) | 5–9 kg | 0.17–0.27 kg |
Limitations
- Targets apply to singleton pregnancies, twins differ.
- The BMI categories use pre-pregnancy weight, not current.
- Individual plans should come from your antenatal provider.
Sources & Review
References used for this calculator’s formulas and thresholds:
Pregnancy Weight Gain FAQ
How much weight should I gain in pregnancy?
Per IOM: 11.5–16 kg if normal BMI pre-pregnancy; 12.5–18 kg underweight; 7–11.5 kg overweight; 5–9 kg with obesity.
When does most pregnancy weight gain happen?
Mostly after week 13, about 0.4 kg/week for normal-BMI women in the second and third trimesters.
What if I gain more than the target?
Occasional fast weeks are normal. Persistent overshooting raises risks of gestational diabetes and large babies, your provider will monitor the curve.
Is it safe to lose weight while pregnant?
Intentional weight loss is not recommended; even with obesity, the goal is to limit gain to 5–9 kg, under supervision.
Please read this first: these results are educational estimates, not medical advice. For decisions about your health, talk to a qualified professional.