What this calculator does
Pregnancy weight gain guideline works out recommended weight gain for a singleton pregnancy, by pre-pregnancy BMI (IOM guidelines). Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Pre-pregnancy weight (kg) | A number, measured in kg. Starts at 65. |
| Height (cm) | A number, measured in cm. Starts at 165. |
| Weeks pregnant (weeks) | A number, measured in weeks. Starts at 20. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with pre-pregnancy weight
Every other input is held at the calculator’s starting values while pre-pregnancy weight varies. Select any row to load that scenario into the calculator.
| Pre-pregnancy weight (kg) | Recommended total gain | Pre-pregnancy BMI category | Typical rate, 2nd/3rd trimester |
|---|---|---|---|
| 32.5 | 12.5 - 18 kg | Underweight (BMI 11.9) | 0.51 kg/week |
| 48.75 | 12.5 - 18 kg | Underweight (BMI 17.9) | 0.51 kg/week |
| 65 | 11.5 - 16 kg | Normal weight (BMI 23.9) | 0.42 kg/week |
| 97.5 | 5 - 9 kg | Obese (BMI 35.8) | 0.22 kg/week |
| 130 | 5 - 9 kg | Obese (BMI 47.8) | 0.22 kg/week |
| 195 | 5 - 9 kg | Obese (BMI 71.6) | 0.22 kg/week |