Pregnancy Weight Gain Calculator
See the recommended total weight gain range for your pre-pregnancy BMI.
Last updated · View algorithm, constants and default inputs (JSON)
Recommended pregnancy weight gain depends on your pre-pregnancy body mass index. These ranges come from the Institute of Medicine guidelines and apply to a single baby.
About this calculator
Recommended pregnancy weight gain depends on your pre-pregnancy body mass index. These ranges come from the Institute of Medicine guidelines and apply to a single baby.
Worked example
calculated with the default values below
Height 165 cm · Weight before pregnancy 62 kg Suggested gain 11.5 – 16 kg · Estimated final weight 73.5 – 78 kg · Pre-pregnancy BMI 22.8 · Recommended total gain from 11.5 kg · Recommended total gain to 16 kg · Target weight at term from 73.5 kg · Target weight at term to 78 kg
General background references
Disclaimer
These calculators are for general information only and are not a medical device, a diagnosis or a treatment plan. Reference ranges describe populations, not individuals, and do not account for pregnancy, medication, disability or athletic training. Discuss your own situation with a qualified healthcare professional.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
BMI = w ÷ (h ÷ 100)²; G: BMI < 18.5 → 12.5–18; < 25 → 11.5–16; < 30 → 7–11.5; ≥ 30 → 5–9
- BMI
- Pre-pregnancy BMI
- w
- Pre-pregnancy weight (kg)
- h
- Height (cm)
- G
- Recommended total gain (kg)
IOM ranges for a singleton pregnancy. Target weight at term = w + G.
Frequently asked questions
Why does an overweight BMI lower the recommended gain to 7-11.5 kg?
The Institute of Medicine bands are keyed to pre-pregnancy BMI: under 18.5 allows 12.5-18 kg, normal 11.5-16, overweight 7-11.5 and obese 5-9. At the default 165 cm and 62 kg the BMI is 22.8, so the tool returns 11.5-16 kg and a term target of 73.5-78 kg. The ranges apply to a single fetus only; twins or medical conditions follow different guidance, which the calculator does not model.