Pregnancy Weight Gain Calculator

Height, cm

Weight before pregnancy, kg

Weight now, kg

Week of pregnancy

Twins (1 for yes)

Result

Assessmentgain is within the recommended range
Gained, kg8
Recommended by this week5.8–9.5 kg
Recommended for the whole pregnancy11.5–16 kg
Rate from the second trimester0.35–0.5 kg a week
BMI before pregnancy22
BMI categorynormal weight

This result is informational only and is not professional advice.

The target depends on the starting weight

Compares actual weight gain against the IOM recommendations for your gestational week and your pre-pregnancy body mass index.

There is no single recommended gain: the higher the pre-pregnancy BMI, the less weight is advised. Underweight is 12.5 to 18 kilograms, normal weight 11.5 to 16, overweight 7 to 11.5, and obesity only 5 to 9.

Gain is also uneven across the pregnancy. The first trimester adds very little — half a kilogram to two over the whole twelve weeks — and the bulk arrives from the second trimester onward at a roughly steady weekly rate that differs by category.

What this calculator shows

The recommended range for your current week and for the whole pregnancy
Your actual gain and how it sits against that range
Pre-pregnancy BMI and the recommended weekly rate

What to keep in mind

The ranges come from the 2009 Institute of Medicine recommendations, which underpin most national guidance.
This is a reference, not a prescription. Your clinician weighs in oedema, multiple pregnancy and any coexisting conditions.

FAQs

How much weight should I gain in pregnancy?

From 5 to 9 kg with obesity up to 12.5 to 18 kg when underweight. At a normal BMI the range is 11.5 to 16 kg.

How much is gained in the first trimester?

Usually half a kilogram to two across the whole twelve weeks. With morning sickness weight sometimes falls, and that is not treated as abnormal.

What weekly rate is normal?

From the second trimester, 0.35 to 0.5 kg a week at a normal starting BMI and 0.17 to 0.27 kg with obesity.

How does it work for twins?

The recommendations rise by roughly half: at a normal BMI that is 17 to 25 kg. The calculator applies a factor of 1.6 when the twins option is on.

Worked example

Week twenty-eight

Input: 165 cm, 60 kg before pregnancy, 68 kg now, week 28

Output: 8 kg gained against a range of 5.8 to 9.5 kg

Note: Pre-pregnancy BMI 22.0 puts this in the normal-weight band, with a second-trimester rate of 0.35 to 0.5 kg a week and a whole-pregnancy target of 11.5 to 16 kg.

Useful links

All tools in Health calculators for weight, lab values and training

Pregnancy Weight Gain Calculator

Result

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