Pregnancy Weight Gain Calculator (Pre-pregnancy BMI & IOM Range)
Enter pre-pregnancy height and weight to get your pre-pregnancy BMI and the IOM recommended total weight gain — e.g. a woman with BMI 22 should gain 11.5–16 kg in pregnancy; add current week and weight to see progress.
For general reference only. Nutrition and weight gain in pregnancy should follow your obstetrician’s guidance.
Your pre-pregnancy BMI and recommended gain range will appear here.
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What is it
The US Institute of Medicine (IOM) sets recommended total pregnancy weight-gain ranges by pre-pregnancy BMI: thinner women should gain more, overweight women less. Appropriate gain supports both mother and baby, but your own plan should follow your obstetrician’s guidance.
Notes & fun facts
A mother who was underweight before pregnancy worries whether she should eat more — seeing the 12.5–18 kg recommended range gives her a clear reference to discuss her diet with her obstetrician.
Origin & history
How much weight to gain in pregnancy was long answered with vague advice like "eat for two". Modern obstetrics replaced it with recommended ranges based on pre-pregnancy BMI: thinner women should gain more, overweight women less. This gives the common worry about whether to eat more a quantitative anchor, and turns gestational weight management into something checkable against a standard.
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