Pregnancy BMI Calculator
Your pre-pregnancy BMI and the weight gain it suggests. Free, private and instant.
How to use the Pregnancy BMI
- Pick metric (cm, kg) or imperial (ft, in, lb) units.
- Enter height.
- Enter weight before pregnancy.
- Press Calculate to get an instant result with a colour scale, chart and plain-English explanation.
About the Pregnancy BMI
Your body mass index before pregnancy guides how much weight gain is healthiest for you and your baby. Enter your height and pre-pregnancy weight to see your BMI category, your recommended total gain and the weight you may reach at term.
Also known as: BMI in pregnancy, pre-pregnancy BMI calculator, pregnancy BMI chart, maternal BMI calculator.
Worked example
- Height: 170 cm
- Weight before pregnancy: 70 kg
Pre-pregnancy BMI: 24.2 kg/m² (Healthy weight). A BMI of 24.2 is healthy weight. For one baby the recommended total pregnancy weight gain is 11.5 kg to 16.0 kg.
- BMI: 24.2
- Category: Healthy weight
- Total gain advised (one baby): 11.5 kg - 16.0 kg
- Expected weight at term: 82 kg - 86 kg
Formula and cut-offs
BMI = weight (kg) / height (m)². Categories: under 18.5 underweight, 18.5-24.9 healthy, 25-29.9 overweight, 30 or more obese. Recommended gain follows IOM guidelines for each category.
Frequently asked questions
What BMI is healthy before pregnancy?
A BMI of 18.5 to 24.9 is considered healthy for most adults.
Does BMI matter in pregnancy?
A very high or low BMI raises the chance of some complications, so doctors tailor advice, such as early glucose testing.
Should I use BMI during pregnancy?
Use your weight before pregnancy. BMI during pregnancy is not meaningful because of baby and fluid weight.
What is the pre-pregnancy BMI for 170 cm and a weight before pregnancy of 70 kg?
Pre-pregnancy BMI: 24.2 kg/m² (Healthy weight). A BMI of 24.2 is healthy weight. For one baby the recommended total pregnancy weight gain is 11.5 kg to 16.0 kg. Enter your own numbers above for a personal result.
Sources and references
- ACOG Committee Opinion 700 - Methods for estimating the due date
- Institute of Medicine (2009) - Weight Gain During Pregnancy: Reexamining the Guidelines
- NHS - Pregnancy guide
Written and checked by the MediHub editorial team against the sources above. Read how we build and review our calculators.
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Last updated . This calculator is for education only and is not medical advice. See the medical disclaimer.