Pregnancy Weight Gain Calculator: How Much Should You Gain?
Gaining too little during pregnancy can restrict fetal growth. Gaining too much increases the risk of gestational diabetes, hypertension, difficult delivery, and postpartum weight retention. The right amount depends on your pre-pregnancy BMI — and this calculator gives you the Institute of Medicine (IOM) recommended range.
IOM Recommended Pregnancy Weight Gain
| Pre-Pregnancy BMI | Category | Recommended Gain |
|---|
| Below 18.5 | Underweight | 12.5–18 kg (28–40 lbs) |
| 18.5–24.9 | Normal | 11.5–16 kg (25–35 lbs) |
| 25.0–29.9 | Overweight | 7–11.5 kg (15–25 lbs) |
| 30.0+ | Obese | 5–9 kg (11–20 lbs) |
| Twin pregnancy (normal BMI) | — | 17–25 kg (37–54 lbs) |
Calculate your personalised range with our free Pregnancy Weight Gain Calculator.
How Weight Is Distributed During Pregnancy
For a woman gaining 13 kg total:
- Baby: ~3.5 kg
- Placenta: ~0.7 kg
- Amniotic fluid: ~0.8 kg
- Uterus growth: ~1.0 kg
- Increased blood volume: ~1.5 kg
- Breast tissue: ~0.5 kg
- Fluid retention: ~2 kg
- Maternal fat stores: ~3 kg
Trimester Weight Gain Rates
First trimester (weeks 1–13): 0.5–2 kg total. Weight gain is minimal — morning sickness may even cause temporary loss.
Second trimester (weeks 14–26): ~0.4–0.5 kg per week for normal BMI. This is when most of the recommended gain occurs.
Third trimester (weeks 27–40): ~0.3–0.4 kg per week. Slows slightly as baby takes up more space.
Practical Tips
Focus on nutrient density, not just calories. Pregnancy requires only 300–500 extra calories per day in the second and third trimesters — not "eating for two" literally.
Prioritise protein, iron, folate, and calcium. These four nutrients are most commonly deficient and most critical for fetal development.
Weigh yourself weekly, not daily. Daily fluctuations from fluid retention can be misleading. Weekly tracking at the same time of day is more informative.
Exercise safely throughout pregnancy. Moderate exercise (150 min/week) is recommended by all major obstetric guidelines for uncomplicated pregnancies.
Final Thoughts
Pregnancy weight gain is one of the most important modifiable factors for maternal and fetal health outcomes. Knowing your personalised target helps you track progress meaningfully and have informed conversations with your midwife or OB.
Find your recommended range with our free Pregnancy Weight Gain Calculator.
Always follow the guidance of your healthcare provider. Individual recommendations may vary based on medical history and pregnancy complications.