# Pregnancy Weight Gain Calculator

URL: https://speedycalculator.com/calculators/health/pregnancy-weight-gain/
Last updated: 2026-10-30

> The pregnancy weight gain calculator shows how much weight is recommended for you to gain in total and by the current week of pregnancy, based on your pre-pregnancy BMI and whether you are expecting twins, using the Institute of Medicine (2009) guidelines.

## Inputs

- Height (cm, in, m, ft, mm)
- Pre-pregnancy weight (kg, lb, st, g)
- Current weight (kg, lb, st, g)
- Weeks pregnant
- Expecting

## Results

- Pre-pregnancy BMI
- BMI category
- Recommended total gain – from
- Recommended total gain – to
- Recommended gain by now – from
- Recommended gain by now – to
- Your gain so far
- Compared with the recommendation

## Formula

```
Pre-pregnancy BMI = weight ÷ height²
Total gain (singleton): underweight 12.5–18 kg, healthy 11.5–16 kg, overweight 7–11.5 kg, obese 5–9 kg
First trimester 0.5–2 kg, then weekly: 0.44–0.58, 0.35–0.50, 0.23–0.33 or 0.17–0.27 kg
```

## Explanation

Gaining the right amount of weight lowers the risk of gestational diabetes, high blood pressure, a very large or small baby and caesarean birth. Most of the gain happens in the second and third trimesters.

### How to use the Pregnancy Weight Gain Calculator

- **Height**
- **Pre-pregnancy weight**
- **Current weight**
- **Weeks pregnant**
- **Expecting**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter your height, weight before pregnancy, current weight and how many weeks pregnant you are.

### IOM 2009 recommendations

Pre-pregnancy BMITotal gain (one baby)Weekly gain, 2nd–3rd trimesterTotal gain (twins)Below 18.512.5–18 kg (28–40 lb)0.44–0.58 kgNo guideline18.5–24.911.5–16 kg (25–35 lb)0.35–0.50 kg17–25 kg25–29.97–11.5 kg (15–25 lb)0.23–0.33 kg14–23 kg30 and above5–9 kg (11–20 lb)0.17–0.27 kg11–19 kg

### Inputs explained

FieldWhat to enterHeightUnits: cm, in, m, ft, mmPre-pregnancy weightUnits: kg, lb, st, gCurrent weightUnits: kg, lb, st, gWeeks pregnantA numberExpectingChoose one: One baby, Twins

### What each result means

- **Pre-pregnancy BMI** = [Pre-pregnancy weight]÷([Height]÷100)^2
- **Your gain so far** = [Current weight] - [Pre-pregnancy weight]

*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Height: 165 cm; Pre-pregnancy weight: 60 kg; Current weight: 66 kg; Weeks pregnant: 20; Expecting: One baby.

Results — Pre-pregnancy BMI = 22; BMI category = Healthy weight; Recommended total gain – from = 11.5 kg; Recommended total gain – to = 16 kg; Recommended gain by now – from = 2.9 kg; Recommended gain by now – to = 5.5 kg; **Your gain so far = 6 kg**; Compared with the recommendation = Above the recommended range.

## Key terms

- **IOM**: Institute of Medicine (now the National Academy of Medicine).

## FAQ

**How much weight should I gain in pregnancy?**
11.5–16 kg (25–35 lb) with a healthy pre-pregnancy BMI.

**Should I eat for two?**
No – you need about 340 extra kcal a day in the second trimester and 450 in the third.

**Is it safe to lose weight in pregnancy?**
Deliberate weight loss is not usually advised; talk to your midwife.


## Sources

- [Institute of Medicine. Weight gain during pregnancy: reexamining the guidelines (2009)](https://nap.nationalacademies.org/catalog/12584/)
- [ACOG Committee Opinion 548 – Weight gain during pregnancy](https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/01/weight-gain-during-pregnancy)