Pregnancy Weight Gain Calculator
Find out how much weight you should gain during pregnancy based on your pre-pregnancy BMI, following IOM (Institute of Medicine) guidelines.
Calculate Your Recommended Weight Gain
Understanding Pregnancy Weight Gain
Gaining the right amount of weight during pregnancy is important for both your health and your baby's development. Too little weight gain can lead to a low birth weight baby, while too much can increase the risk of gestational diabetes, high blood pressure, and complications during delivery.
IOM Weight Gain Recommendations
| BMI Category | BMI Range | Recommended Gain |
|---|---|---|
| Underweight | < 18.5 | 12.5 - 18 kg |
| Normal weight | 18.5 - 24.9 | 11.5 - 16 kg |
| Overweight | 25 - 29.9 | 7 - 11.5 kg |
| Obese | ≥ 30 | 5 - 9 kg |
Got questions?
Frequently Asked Questions
Weight gain recommendations depend on your pre-pregnancy BMI. Underweight women (BMI < 18.5) should gain 12.5-18 kg, normal weight (BMI 18.5-24.9) should gain 11.5-16 kg, overweight (BMI 25-29.9) should gain 7-11.5 kg, and obese (BMI 30+) should gain 5-9 kg.
Most weight gain occurs in the second and third trimesters. In the first trimester, you might gain 1-2 kg total. From the second trimester onwards, expect to gain about 0.5 kg per week for normal weight women.
It is not recommended to diet or try to lose weight during pregnancy. Even if you are overweight, your body needs adequate nutrition for your baby's growth. Focus on eating nutritious foods and staying active. Speak to your healthcare provider about healthy eating plans.
A typical breakdown: baby (3-3.5 kg), placenta (0.7 kg), amniotic fluid (0.8 kg), increased blood volume (1.2 kg), uterus growth (0.9 kg), breast tissue (0.5 kg), fat stores for breastfeeding (2-4 kg), and extra fluids (1.5 kg).
About the Author
Due Date Calculator SA Editorial Team
Our content is reviewed by healthcare professionals familiar with South African maternal health practices. We combine evidence-based medical information with local knowledge to support South African mums throughout their pregnancy journey. Our team includes contributors with backgrounds in midwifery, obstetrics, and maternal health education.
Last reviewed: