Pregnancy Weight Gain Calculator (How Much Should I Gain?)
Finds your BMI group from pre-pregnancy weight and height and shows the recommended total and weekly weight gain for a singleton pregnancy (IOM 2009).
Things to keep in mind:
- The ranges are for singleton pregnancies; recommendations for twins and multiples differ.
- For adolescent pregnancies, gestational diabetes, pre-eclampsia or other conditions your doctor sets the weight target.
- This tool is not medical advice; see your doctor if you notice sudden weight gain, swelling or weight loss.
Calculator
Result
Enter the values and press Calculate to see the result here.
About this tool
The recommended weight gain during pregnancy is not the same for everyone; it depends on the body mass index (BMI) before pregnancy. The most widely used reference is the set of ranges published by the US Institute of Medicine (IOM, 2009) for singleton pregnancies. This tool calculates your BMI from pre-pregnancy weight and height, shows your group and lists the recommended total and weekly weight gain for that group.
Formula and recommended ranges
BMI = pre-pregnancy weight (kg) ÷ height (m)² (rounded to 1 decimal)
| Pre-pregnancy BMI | Group | Total gain | Weekly in 2nd and 3rd trimester |
|---|---|---|---|
| < 18.5 | Underweight (1) | 12.5–18 kg | 0.44–0.58 kg |
| 18.5–24.9 | Normal (2) | 11.5–16 kg | 0.35–0.50 kg |
| 25.0–29.9 | Overweight (3) | 7–11.5 kg | 0.23–0.33 kg |
| ≥ 30.0 | Obese (4) | 5–9 kg | 0.17–0.27 kg |
The IOM calculations assume a total gain of 0.5–2 kg in the first trimester (first 13 weeks); the weekly ranges apply to the second and third trimesters.
Example
Pre-pregnancy weight 60 kg, height 165 cm: BMI = 60 ÷ 1.65² = 22.0 → normal group. Recommended total gain 11.5–16 kg, from the second trimester 0.35–0.50 kg per week. If you weigh 66.5 kg now, you have gained 6.5 kg so far.
How to read the result
Treat the ranges as a target band: gaining well above or below the band in weekly follow-ups is something to discuss with your doctor. Timing matters too — the same total gain means different things in different weeks. Use the pregnancy week calculator to find your current week.
How to use
- Enter your pre-pregnancy weight (before your last menstrual period).
- Enter your height in centimetres.
- Optionally enter your current weight to see how much you have gained so far.
- Check the recommended total and weekly gain for your BMI group.
Notes
BMI is rounded half-up to 1 decimal and the group is determined from the rounded value (e.g. 24.96 → 25.0 → overweight). Ranges are the IOM (2009) singleton recommendations; the weekly range applies to the second and third trimesters. Without a current weight, "gained so far" shows 0.
Sources
References
- [1]Weight Gain During Pregnancy: Reexamining the GuidelinesInstitute of Medicine / National Academies Press, 2009
Frequently asked questions
For a woman with a normal pre-pregnancy BMI (18.5–24.9) the IOM recommends a total of 11.5–16 kg. Underweight women are advised 12.5–18 kg, overweight women 7–11.5 kg and obese women 5–9 kg.
The IOM calculations assume 0.5–2 kg in total during the first trimester. Because of nausea, gaining nothing or losing a little in this period also happens and is assessed with your doctor.
Recommendations depend on the starting body build. Current weight during pregnancy includes the baby, placenta, amniotic fluid and the increased blood volume, so it is not used to determine the BMI group.
Gaining well above the range is associated with gestational diabetes, high blood pressure, a large baby and retained weight after birth; staying below it can raise the risk of low birth weight. Agree on your personal target with your doctor.
Next step
Related tools to continue your calculation.
- Calculate
Pregnancy Week and Due Date Calculator
Calculate your estimated due date (Naegele's rule), how many weeks pregnant you are, the days left and your trimester dates from the first day of your last period.
- Calculate
Body Mass Index (BMI) Calculator
Calculate your body mass index (BMI) from weight and height, see your WHO class, the healthy weight range for your height and how much weight separates you from it.
- Calculate
BMR and Daily Calorie Needs Calculator
Calculate your basal metabolic rate (BMR) with the Mifflin-St Jeor equation and your daily calorie needs from your activity level, plus daily calories for a weight loss or gain goal.
- Calculate
Ideal Weight Calculator (Devine, Robinson, Miller, Hamwi)
Estimate your ideal body weight from height and sex with four classic formulas (Devine, Robinson, Miller, Hamwi), their average and the BMI-based healthy weight range.
- Calculate
Ovulation and Fertile Window Calculator
Estimate your ovulation day, fertile window (most fertile days) and next period from the first day of your last period and your cycle length.