Ensuring a healthy pregnancy starts with tracking your growth. Our Pregnancy Weight Gain Calculator uses the official Institute of Medicine (IOM) guidelines to determine your safe weight range based on your pre-pregnancy BMI. Whether you are expecting one baby or twins, this tool provides a personalized target for your total gain and a breakdown of where you should be right now.
Pregnancy Weight Gain Calculator
Based on 2009 IOM Guidelines
How much weight should I gain?
The amount of weight you should gain depends entirely on your Body Mass Index (BMI) before you got pregnant. There is no "one size fits all" number.
According to the 2009 IOM guidelines used by most obstetricians:
- Underweight (BMI < 18.5): 28–40 lbs (12.5–18 kg)
- Normal Weight (BMI 18.5–24.9): 25–35 lbs (11.5–16 kg)
- Overweight (BMI 25–29.9): 15–25 lbs (7–11.5 kg)
- Obese (BMI ≥ 30): 11–20 lbs (5–9 kg)
Weight Gain with Twins
If you are carrying twins, your nutritional needs are higher. Our calculator adjusts automatically for multiple pregnancies, where the recommended gain typically ranges from 37 to 54 lbs (17–25 kg) for women with a normal BMI.
Where does the weight go?
It's not just fat! A significant portion of your pregnancy weight comes from the baby, placenta, amniotic fluid, and increased blood volume.
- Baby: ~7.5 lbs
- Placenta & Fluid: ~3.5 lbs
- Increased Blood & Fluids: ~7–8 lbs
- Uterus & Breasts: ~4 lbs
- Maternal Fat Stores: ~7 lbs (Essential for breastfeeding)