Pregnancy Weight Gain Range Calculator
Recommended pregnancy weight gain depends on your pre-pregnancy body mass index. For a single baby, the National Academies (Institute of Medicine) guidelines that U.S. obstetric care follows give four total-gain ranges by BMI category. This calculator computes your pre-pregnancy BMI from your height and weight, identifies your category, and shows the recommended total weight-gain range in pounds. It is a reference tool for singleton pregnancies and not a substitute for the advice of your own obstetric provider, who may set a different target for your situation.
Pregnancy weight gain ranges
BMI = weight kg / (height m)^2
BMI under 18.5 (underweight): 28 to 40 lb
BMI 18.5 to 24.9 (normal): 25 to 35 lb
BMI 25 to 29.9 (overweight): 15 to 25 lb
BMI 30 or above (obese): 11 to 20 lb
These total-gain ranges are the National Academies (IOM) recommendations for a single baby. They are population guidelines; your provider may individualize them.
Pregnancy weight gain context
- First-trimester gain is typically small, often 1 to 5 pounds in total.
- Most recommended gain occurs in the second and third trimesters at a steadier weekly rate.
- The ranges differ for twins; ask your provider about multiple pregnancies.
- Both too little and too much gain carry risks; your provider tailors the target to you.
- This tool is for reference only and is not medical advice.
Pregnancy weight gain: frequently asked questions
How much weight should I gain during pregnancy?
The recommended total gain depends on your pre-pregnancy body mass index. For a single baby the National Academies (Institute of Medicine) guidelines advise 28 to 40 pounds if underweight (BMI under 18.5), 25 to 35 pounds if normal weight (18.5 to 24.9), 15 to 25 pounds if overweight (25 to 29.9), and 11 to 20 pounds if obese (30 or above).
How is pre-pregnancy BMI calculated?
Body mass index equals weight in kilograms divided by height in meters squared. This calculator converts pounds and inches for you. Your BMI category then selects the recommended total weight-gain range from the National Academies guidelines used by U.S. obstetric care.
Do these ranges apply to twins?
No. These figures are for a single pregnancy. The National Academies give separate, higher ranges for twins, and triplet or higher pregnancies need individualized advice. This calculator covers singleton pregnancies; ask your provider about multiples.
How is weight gain spread across pregnancy?
Gain is usually small in the first trimester (often 1 to 5 pounds total) and then steadier through the second and third trimesters. The guidelines express the bulk of the recommended gain as a weekly rate in the second and third trimesters, which is why mid-pregnancy weeks see the most change.
Is this calculator medical advice?
No. It reports the published population ranges for reference only. Your provider may recommend a different target based on your health, the baby's growth, and other factors. Always follow the guidance of your own obstetric care team.
Official sources
- National Academies of Sciences, Engineering, and Medicine: Weight Gain During Pregnancy guidelines.
- U.S. Centers for Disease Control and Prevention: Maternal and Infant Health.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.