About this calculator
The Pregnancy BMI Calculator helps estimate adult BMI from height and weight. For pregnancy weight-gain guidance, the most useful value is usually pre-pregnancy BMI.
BMI is a screening tool, not a diagnosis. It does not measure body composition, fetal growth, fluid retention, or pregnancy complications.
BMI is calculated as weight in kilograms divided by height in meters squared. For pregnancy weight-gain guidance, pre-pregnancy BMI category is used; BMI during pregnancy is not interpreted the same way as nonpregnant adult BMI.
Activated — adult BMI screening estimate
Pregnancy BMI category is based on pre-pregnancy or early-pregnancy weight and may not reflect body composition or individual risk.
Formula and method
BMI = weight (kg) ÷ height (m)^2. The calculator maps the result to standard adult BMI categories and explains whether the entered weight should be used for pregnancy weight-gain guidance.
Limitations and when not to rely on this result
- Pregnancy BMI category is based on pre-pregnancy or early-pregnancy weight and may not reflect body composition or individual risk.
- High-risk pregnancy, adolescents, multiple pregnancy, edema, eating disorders, or major weight change need individualized care.
- Do not use BMI alone to judge pregnancy health.
Frequently asked questions
Should I use pre-pregnancy or current weight? +
Use pre-pregnancy weight if you want the BMI category used for pregnancy weight-gain recommendations. Current pregnancy weight changes normally as pregnancy progresses.
Are BMI categories different during pregnancy? +
Standard adult BMI categories are used for pre-pregnancy BMI. Current pregnancy BMI should not be interpreted like nonpregnant BMI.
Does BMI diagnose health? +
No. BMI is a screening measure and should be considered with medical history, labs, body composition, and clinical assessment.
How does BMI link to pregnancy weight gain? +
IOM/CDC pregnancy weight-gain ranges are based on pre-pregnancy BMI category.
What if I do not know my pre-pregnancy weight? +
Use your earliest recorded prenatal weight if available and discuss the estimate with your obstetric clinician.