Pregnancy Weight Gain Calculator

How much weight should I gain during pregnancy?

The healthy amount depends on your weight before pregnancy, measured by your body mass index (BMI). Women who start with a lower BMI need to gain more, and women who start with a higher BMI need to gain less. These are the Institute of Medicine (IOM) guidelines for a single baby:

Pre-pregnancy BMI	Total gain	Per week (2nd & 3rd trimester)
Underweight (below 18.5)	12.5 – 18 kg (28 – 40 lbs)	0.44 – 0.58 kg (1 – 1.3 lbs)
Normal (18.5 – 24.9)	11.5 – 16 kg (25 – 35 lbs)	0.35 – 0.50 kg (0.8 – 1 lb)
Overweight (25 – 29.9)	7 – 11.5 kg (15 – 25 lbs)	0.23 – 0.33 kg (0.5 – 0.7 lb)
Obese (30 and above)	5 – 9 kg (11 – 20 lbs)	0.17 – 0.27 kg (0.4 – 0.6 lb)

Example: a woman who is 160 cm tall and weighed 58 kg before pregnancy has a BMI of 22.7, which is normal. Her healthy total gain is 11.5 to 16 kg. By week 20 she would usually have gained about 3.4 to 5.6 kg.

Weight gain for twins

For twins, the IOM provisional guidelines are 17 – 25 kg (37 – 54 lbs) for normal BMI, 14 – 23 kg (31 – 50 lbs) for overweight and 11 – 19 kg (25 – 42 lbs) for obese. There is not enough evidence to set a range for underweight women carrying twins, so a doctor will advise individually.

Where does the weight go?

Only part of the weight you gain is the baby. For a typical total gain of about 13 to 14 kg, it is roughly made up of:

Part	Approximate weight
Baby	3.4 kg (7.5 lbs)
Placenta	0.7 kg (1.5 lbs)
Amniotic fluid	0.9 kg (2 lbs)
Larger uterus	0.9 kg (2 lbs)
Breast tissue	0.9 kg (2 lbs)
Extra blood	1.8 kg (4 lbs)
Extra body fluid	1.8 kg (4 lbs)
Fat stores for breastfeeding	3.2 kg (7 lbs)

Why the right amount matters

Gaining too little is linked to a higher chance of a small baby and premature birth. Gaining too much is linked to gestational diabetes, high blood pressure, a larger baby, a harder delivery and extra weight that stays after birth. Staying roughly within your range lowers these risks, but small differences are normal and not a cause for worry.

Tips for healthy weight gain

You do not need to "eat for two". In the first trimester most women need no extra calories. In the second trimester you need about 340 extra calories a day, and in the third about 450, roughly a glass of milk and a sandwich. Choose filling, nutritious foods such as dal, eggs, yogurt, fruit, vegetables and whole grains, and limit sugary drinks and fried snacks. Gentle activity like walking for 30 minutes most days is safe for most pregnancies, but check with your doctor first. Never try to lose weight or diet while pregnant unless your doctor advises it.

Frequently asked questions

How much weight should I gain in pregnancy by week?

Most women gain 0.5 to 2 kg in the first 13 weeks, then about 0.35 to 0.5 kg a week if they started at a normal weight. Enter your week above to see your personal range.

Is it normal to lose weight in the first trimester?

A small loss is common because of nausea and vomiting. If you cannot keep food or fluids down, or you lose a lot of weight, contact your doctor, as severe sickness needs treatment.

Should I use my current weight or my weight before pregnancy?

Use your weight before pregnancy, or your weight at your first check-up if you do not know it. Your pre-pregnancy BMI decides your target range.

How many calories do I need when pregnant?

About the same as before in the first trimester, around 340 extra a day in the second and around 450 extra a day in the third. Use the Calorie Calculator to find your starting point.

How much weight will I lose after giving birth?

Most women lose about 5 to 6 kg at birth, from the baby, placenta and fluid, and more over the following weeks. Breastfeeding can help, and most women return close to their pre-pregnancy weight within 6 to 12 months.