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Pregnancy weight gain calculator

See how much weight is usually gained in pregnancy for your starting BMI, and how much per week in the second and third trimesters. This is a guide to talk through with your care team, not a target to hit.

Important: These ranges come from US guidelines (National Academy of Medicine, 2009) and are a general guide, not a target. Guidance differs between countries. In the UK, for example, midwives record your weight at the booking appointment, but routine weighing afterwards is not recommended and there are no official week-by-week targets. Some health services use different BMI cut-offs for people of South or East Asian background. Your midwife or doctor will advise what is right for you. Do not try to lose weight or restrict food during pregnancy without medical advice.

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How much weight do people usually gain?

The ranges depend on your body mass index (BMI) before you became pregnant. For one baby, the US guidelines are:

BMI below 18.5 (underweight): 28 to 40 lb (12.5 to 18 kg)
BMI 18.5 to 24.9 (healthy weight): 25 to 35 lb (11.5 to 16 kg)
BMI 25 to 29.9 (overweight): 15 to 25 lb (7 to 11.5 kg)
BMI 30 or above: 11 to 20 lb (5 to 9 kg)

The NHS describes a typical gain of about 10 to 12.5 kg (22 to 28 lb), most of it after week 20, without setting a target for each person. Most of the gain happens after the first trimester. Many people gain very little in the first 12 weeks, and some lose a little because of nausea and vomiting. Read about morning sickness and hyperemesis if sickness is making it hard to eat.

Where does the weight go?

Only part of the extra weight is fat. As a rough guide, for a total gain of about 30 lb (13.5 kg):

Your baby: about 7.5 lb (3.4 kg)
Placenta: about 1.5 lb (0.7 kg)
Amniotic fluid: about 2 lb (0.9 kg)
Growing womb: about 2 lb (0.9 kg)
Breast tissue: about 2 lb (0.9 kg)
Extra blood: about 3 to 4 lb (1.4 to 1.8 kg)
Extra body fluid: about 4 lb (1.8 kg)
Fat stores for breastfeeding and recovery: about 6 to 8 lb (2.7 to 3.6 kg)

Looking after yourself rather than chasing a number

You do not need to "eat for two". Most people need only a small amount of extra energy, and only in the last trimester. See our guide to a healthy pregnancy diet.
Regular, gentle activity helps with energy, mood and sleep. Read about safe exercise in pregnancy.
Do not diet or cut out food groups while you are pregnant unless a doctor or dietitian advises it.
If gaining weight or being weighed is stressful for you, for example because of a past history of eating difficulties, tell your midwife or doctor. They can support you without making weight the focus.

When weight changes need attention

Tell your midwife or doctor if you are losing weight, cannot keep food down, or are gaining weight very quickly. Sudden swelling of the face or hands, a severe headache or changes in your vision can be signs of pre-eclampsia and need same-day advice. Read about pre-eclampsia and other pregnancy warning signs. Weight and blood sugar are also checked if you have gestational diabetes.

Official guidance: NHS: weight gain in pregnancy. Also try our due date calculator.