Pregnancy Weight Calculator
Calculate your recommended pregnancy weight gain by week and trimester based on your pre-pregnancy BMI and IOM guidelines.
How to Use This Tool
- Enter your pre-pregnancy weight and height — this is used to calculate your starting BMI category.
- Enter your current week of pregnancy (1-40) and your current weight.
- Select "Calculate Gain" to see your recommended total gain so far, your progress status, and a visual breakdown.
Why Tracking Pregnancy Weight Gain Matters
Gaining an appropriate amount of weight during pregnancy supports healthy fetal growth and development, while gaining significantly more or less than recommended is linked to a higher risk of complications — including gestational diabetes, high blood pressure, a difficult delivery, or a baby that's unusually large or small for its gestational age. Tracking your progress against evidence-based guidelines helps you and your care provider spot and address any concerns early, rather than only at your next appointment.
Understanding Your Results
This calculator uses your pre-pregnancy BMI to place you into one of four categories used by the U.S. Institute of Medicine (IOM), each with its own total recommended gain for a single-baby pregnancy:
| Pre-Pregnancy BMI | Category | Total Recommended Gain |
|---|---|---|
| Below 18.5 | Underweight | 12.5 – 18 kg |
| 18.5 – 24.9 | Normal weight | 11.5 – 16 kg |
| 25 – 29.9 | Overweight | 7 – 11.5 kg |
| 30 and above | Obese | 5 – 9 kg |
Your "recommended gain so far" is estimated by spreading your total target gain across the full 40 weeks (with most of it concentrated in the second and third trimesters, since first-trimester gain is typically minimal). Your status — on track, ahead, or behind — simply compares your actual gain to that expected pace; it's a general guide, not a clinical judgment, and normal week-to-week fluctuation is expected.
Typical Gain by Trimester
| Trimester | Typical Gain (normal pre-pregnancy weight) |
|---|---|
| First (weeks 1-13) | 0.5 – 2 kg total (sometimes less, due to nausea) |
| Second (weeks 14-27) | ~0.3 – 0.5 kg per week |
| Third (weeks 28-40) | ~0.3 – 0.5 kg per week |
What If I'm Carrying Twins?
Recommended gain is higher for a twin pregnancy — roughly 16.5-24.5 kg for normal pre-pregnancy weight, 14-22.5 kg for overweight, and 11-19 kg for obese women. This calculator is built for single-baby pregnancies, so if you're expecting twins or multiples, use these figures as a general reference and work closely with your OB-GYN for a plan tailored to your situation.
Healthy Tips
- Focus on nutrient-dense foods, especially folate, iron, calcium, and protein — quality matters more than simply "eating for two."
- Weigh yourself at a consistent time (like first thing in the morning) for the most comparable week-to-week readings.
- Light, doctor-approved activity such as walking or prenatal yoga can support a healthy pace of gain and make delivery recovery easier.
- Don't try to lose weight during pregnancy to "correct" a fast pace of gain — talk to your doctor instead, who can rule out other causes and adjust your plan safely.
- Postpartum, most guidelines suggest waiting 6-8 weeks (longer if breastfeeding is being established) before starting any intentional weight loss plan, and a modest ~500 calorie/day deficit alongside gentle exercise is a commonly recommended starting point.
FAQs
How much weight should I gain during pregnancy?
It depends on your pre-pregnancy BMI. The Institute of Medicine recommends about 12.5-18 kg for underweight women, 11.5-16 kg for normal weight, 7-11.5 kg for overweight, and 5-9 kg for obese women, carrying a single baby.
How much should I gain per trimester?
Most guidelines suggest very little gain in the first trimester (0.5-2 kg total), then roughly 0.3-0.5 kg per week through the second and third trimesters for a woman of normal pre-pregnancy weight.
What if I'm carrying twins?
Recommended gain is higher — commonly around 16.5-24.5 kg for normal weight, 14-22.5 kg for overweight, and 11-19 kg for obese women — though your doctor should individualize this for you.
What does "on track", "ahead", or "behind" mean in my results?
It compares your actual gain so far to the expected amount for your current week and BMI category. It's a general guide, not a medical judgment — your doctor is the best source for whether your progress is right for you.
Is it safe to try to lose weight during pregnancy?
Intentional weight loss during pregnancy is not generally recommended, even for women who are overweight, unless specifically advised by a doctor.
How do I lose pregnancy weight safely afterward?
Most guidelines suggest waiting at least 6-8 weeks postpartum, then a modest ~500 calorie/day deficit alongside gentle, doctor-approved exercise tends to be a safe, sustainable approach.
When to Consult a Doctor
Contact your care provider if you notice a sudden, large weight gain in a short period (which can signal fluid retention or preeclampsia), if you're gaining very little or losing weight, or if you have any concerns about your progress — this calculator is a general reference, not a substitute for the individualized monitoring your prenatal appointments provide.