Pregnancy Weight Gain Calculator
Look up the IOM recommended total pregnancy weight-gain range for your pre-pregnancy BMI class, plus the recommended range so far at your current week.
IOM pregnancy weight-gain guidelines last updated · reference source
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Dated static reference; no live data is fetched. Verify current source values and assumptions before relying on results.
What this tool does
Look up the IOM recommended total pregnancy weight-gain range for your pre-pregnancy BMI class, plus the recommended range so far at your current week. IOM/National Academies 2009 ranges for a singleton pregnancy. Twin ranges differ (e.g. normal-BMI twin range 37–54 lb) and are not shown. Individual guidance from your maternity clinician overrides any table.
How to use the Pregnancy Weight Gain Calculator
- Enter or select pre-pregnancy weight in lb.
- Enter or select height in in.
- Enter or select current week of pregnancy.
- Read the calculated result; change any measurement to compare alternatives.
Formula
pre-pregnancy BMI selects the IOM (2009) total-gain range; cumulative range at a week = IOM first-trimester range (1.1–4.4 lb) + weekly rate range × (week − 13) after week 13
- weight
- Pre-pregnancy weight (lb, before metric conversion)
- height
- Height (in, before metric conversion)
- week
- Current week of pregnancy
IOM/National Academies 2009 ranges for a singleton pregnancy. Twin ranges differ (e.g. normal-BMI twin range 37–54 lb) and are not shown. Individual guidance from your maternity clinician overrides any table.
Worked example
For pregnancy weight gain calculator, the following measurements illustrate the exact method: Pre-pregnancy weight: 150; Height: 65; Current week of pregnancy: 20.
Inputs
- Pre-pregnancy weight150 lb
- Height65 in
- Current week of pregnancy20
Result
- Pre-pregnancy BMI24.96
- IOM BMI classNormal weight
- Recommended total gain (lb)25–35
- Recommended gain so far by week 20 (lb)6.7–11.4
IOM recommended total gain (singleton)
| Pre-pregnancy class | BMI | Total gain (lb) | Rate in 2nd/3rd trimester (lb/week) |
|---|---|---|---|
| Underweight | BMI below 18.5 | 28–40 | 1–1.3 |
| Normal weight | BMI 18.5–24.9 | 25–35 | 0.8–1 |
| Overweight | BMI 25.0–29.9 | 15–25 | 0.5–0.7 |
| Obesity | BMI 30.0 or above | 11–20 | 0.4–0.6 |
Results explained
- Pre-pregnancy BMI
- Pre-pregnancy BMI from the formula above. IOM/National Academies 2009 ranges for a singleton pregnancy. Twin ranges differ (e.g. normal-BMI twin range 37–54 lb) and are not shown. Individual guidance from your maternity clinician overrides any table.
- IOM BMI class
- IOM BMI class from the formula above. IOM/National Academies 2009 ranges for a singleton pregnancy. Twin ranges differ (e.g. normal-BMI twin range 37–54 lb) and are not shown. Individual guidance from your maternity clinician overrides any table.
- Recommended total gain (lb)
- Recommended total gain (lb) from the formula above. IOM/National Academies 2009 ranges for a singleton pregnancy. Twin ranges differ (e.g. normal-BMI twin range 37–54 lb) and are not shown. Individual guidance from your maternity clinician overrides any table.
- Recommended gain so far by week 20 (lb)
- Recommended gain so far by week 20 (lb) from the formula above. IOM/National Academies 2009 ranges for a singleton pregnancy. Twin ranges differ (e.g. normal-BMI twin range 37–54 lb) and are not shown. Individual guidance from your maternity clinician overrides any table.
Frequently asked questions
The IOM (2009) singleton ranges by pre-pregnancy BMI: underweight 28–40 lb, normal weight 25–35 lb, overweight 15–25 lb, obesity 11–20 lb. This tool selects your class from your pre-pregnancy BMI.
IOM describes a small first-trimester total (about 1.1–4.4 lb) followed by a steady weekly rate in the 2nd and 3rd trimesters (e.g. 0.8–1 lb/week for normal BMI). The calculator combines the two for your week.
Higher: normal BMI 37–54 lb, overweight 31–50 lb, obesity 25–42 lb (provisional IOM figures). This calculator shows singleton ranges only.
A single week's position is not a verdict; gain is uneven week to week. Persistent deviation is a conversation for your maternity clinician, who considers the whole pregnancy picture.
No. It reproduces the published IOM table arithmetic. Conditions such as pre-eclampsia, gestational diabetes or growth concerns change individual guidance.