WorldCalcs

Pregnancy Weight Gain Calculator

Recommended total and cumulative pregnancy weight gain from your pre-pregnancy BMI, using the 2009 IOM guidelines.

Reviewed by the WorldCalcs team · Methodology · Last reviewed: June 2026

Pre-pregnancy BMI

22.0 — Normal weight

Recommended total gain (singleton)

11.5–16.0 kg (25–35 lb)

Cumulative target at week 20

2.9–5.5 kg

This tool provides general estimates for information only and is not medical advice. Always confirm dates and targets with your doctor or midwife. See our full disclaimer.

What this calculator shows

Given your pre-pregnancy weight, height and current week, this tool estimates your starting BMI category and the total pregnancy weight gain recommended by the 2009 Institute of Medicine (IOM) guidelines. For a singleton pregnancy it also gives a cumulative target range at your current week, so you can see whether your gain so far is within the suggested band.

How pregnancy weight-gain targets are set

The IOM recommendations are based on pre-pregnancy BMI: lower starting BMI → higher recommended gain, higher BMI → lower gain. Roughly 0.5–2 kg (1–4.5 lb) is expected in the first trimester, then a steady weekly gain in the second and third trimesters — around 0.35–0.5 kg per week for a normal-BMI singleton pregnancy. Twin ranges are higher; there is no formal twin recommendation for underweight women.

Example

A woman who is 1.65 m and weighed 60 kg before pregnancy has a BMI of 22.0 — the normal-weight range. Her recommended total gain is 11.5–16 kg (25–35 lb). By week 20, a healthy cumulative gain is roughly 2.9–5.5 kg.

Related: BMI Calculator, Pregnancy Calculator, Calorie Calculator.

All calculations happen in your browser. Nothing is sent, stored, or tracked.

Results are estimates and may contain errors — for general information only, not professional advice. Always verify before relying on them. Disclaimer

How to use

Enter your pre-pregnancy weight and height (metric or imperial), the current week of pregnancy, and — if you want a check — your current weight. Choose singleton or twins. The tool returns your pre-pregnancy BMI, the recommended total gain and — for a single pregnancy — a cumulative target for the current week.

Frequently asked questions

How much weight should I gain during pregnancy?+

It depends on your weight before pregnancy. Using the 2009 Institute of Medicine guidelines, a normal-BMI woman is advised to gain 11.5–16 kg (25–35 lb) over a single pregnancy; underweight women more and overweight or obese women less.

How is the recommendation decided?+

It is based on your pre-pregnancy body mass index (BMI). Lower starting BMI means a higher recommended gain, and higher starting BMI means a lower one.

How much weight should I gain each week?+

Very little in the first trimester, about 0.5–2 kg (1–4.5 lb) total. After that, a normal-BMI woman gains roughly 0.35–0.5 kg (about a pound) per week through the second and third trimesters.

How much weight gain is normal in the first trimester?+

Around 0.5–2 kg (1–4.5 lb) in total. Many women gain little or even lose a little early on due to nausea, which is usually fine.

What if I'm expecting twins?+

Recommended gain is higher. For a normal-BMI twin pregnancy the guideline is about 16.8–24.5 kg (37–54 lb); overweight and obese ranges are lower. There is no formal twin guideline for underweight women.

What if I started overweight or obese?+

The recommended total is lower, about 7–11.5 kg (15–25 lb) if overweight and 5–9 kg (11–20 lb) if obese, because you begin with more energy stores.

Where does the pregnancy weight actually go?+

It is spread across the baby, placenta, amniotic fluid, extra blood and body fluid, a larger uterus and breasts, and some fat stores for breastfeeding, not just the baby's weight.

Is it safe to lose weight while pregnant?+

Deliberately dieting to lose weight during pregnancy is generally not advised. If weight is a concern, talk to your doctor or midwife about a safe plan.

References

  • Institute of Medicine and National Research Council (2009), Weight Gain During Pregnancy: Reexamining the Guidelines.

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