How much weight should I gain during pregnancy?

For a single baby, IOM/ACOG recommend about 28-40 lb if you started underweight, 25-35 lb at a normal BMI, 15-25 lb if overweight, and 11-20 lb if you began with obesity. Your provider may adjust this for your situation.

How is the recommendation calculated?

It is based on your pre-pregnancy BMI (weight and height before pregnancy). This calculator computes your BMI, places you in a category, and shows the matching IOM/ACOG total range and approximate weekly rate.

How much weight gain is normal in the first trimester?

First-trimester gain is usually small, often around 1-4 lb total, with most weight gained in the second and third trimesters at a steadier weekly pace.

Should I gain more weight if I'm having twins?

Yes, twin pregnancies have higher recommended ranges (for example, about 37-54 lb at a normal pre-pregnancy BMI). Specific guidance, especially for the underweight category, should come from your provider.

Is it safe to try to lose weight while pregnant?

You should not try to lose weight or restrict gestational weight gain by dieting during pregnancy without medical supervision, even if you started at a higher weight. Talk to your provider about a healthy plan for you.

Pregnancy Weight Gain Calculator

Enter your pre-pregnancy height and weight and your current week of pregnancy to see the recommended total weight gain and where you should roughly be by now, based on the widely used Institute of Medicine (IOM) / ACOG guidelines. These are general targets for healthy pregnancies — your own doctor's advice always comes first.

Educational information, not medical advice. This calculator uses published IOM/ACOG ranges for general guidance. Healthy weight gain in pregnancy is individual, and your obstetric provider may recommend something different based on your health, your baby, and your circumstances. Always follow your doctor's or midwife's advice. Operator: Mustafa Bilgic.

Your IOM/ACOG guidance

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recommended total weight gain for the full pregnancy

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Pre-preg BMI

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BMI category

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Approx. by week

Recommended rate (2nd & 3rd trimester)

Remember: first-trimester gain is usually small (often about 1–4 lb total). Most gain happens in the second and third trimesters at a steadier weekly pace. These figures are general estimates — follow your provider's personalized guidance.

How much weight should you gain in pregnancy?

The most widely used guidance comes from the U.S. Institute of Medicine (IOM, now the National Academy of Medicine) and is endorsed by the American College of Obstetricians and Gynecologists (ACOG). Recommended total weight gain depends mainly on your pre-pregnancy body mass index (BMI):

Pre-pregnancy BMI	Category	Single baby	Twins
Below 18.5	Underweight	28–40 lb	(ask your provider)
18.5–24.9	Normal weight	25–35 lb	37–54 lb
25.0–29.9	Overweight	15–25 lb	31–50 lb
30.0 and above	Obese	11–20 lb	25–42 lb

Source: IOM (2009) gestational weight gain guidelines, as summarized by ACOG and the CDC. For twins where the underweight category applies, guidance is individualized — ask your provider.

How the weekly rate works

Most weight gain happens after the first trimester. After early pregnancy, the guidelines describe a roughly steady weekly rate. For a single baby, the commonly cited rates are about 1 lb/week for those starting underweight, ~0.8–1 lb/week for normal weight, ~0.6 lb/week for overweight, and ~0.5 lb/week for those starting with obesity. First-trimester gain is usually small (often 1–4 lb total). This calculator uses these published ranges to estimate roughly where your cumulative gain might be by your current week.

Why healthy pregnancy weight gain matters

Gaining within the recommended range supports your baby's growth while reducing risks linked to gaining too little (such as a smaller baby) or too much (such as gestational diabetes, high blood pressure, and difficulty losing weight afterward), according to ACOG and the CDC. Because every pregnancy is different, your provider individualizes this guidance — for instance, if you're carrying multiples, started outside the usual BMI ranges, or have a medical condition.

Mustafa Bilgic

Operator of WeightGain.us, based in Adıyaman, Türkiye. Mustafa is an independent publisher, not a medical professional; all ranges here are taken from the published IOM/ACOG/CDC guidelines and attributed to those bodies. For personal advice about your pregnancy, consult your obstetric provider.

When to call your provider: contact your obstetric provider about sudden or rapid weight gain, very little or no gain over time, or significant swelling, which can need medical evaluation. Never try to restrict weight gain or diet to lose weight during pregnancy without medical supervision.

Frequently asked questions

How much weight should I gain during pregnancy?: For a single baby, IOM/ACOG recommend about 28–40 lb if you started underweight, 25–35 lb at a normal BMI, 15–25 lb if overweight, and 11–20 lb if you began with obesity. Your provider may adjust this for your situation.
How is the recommendation calculated?: It is based on your pre-pregnancy BMI (weight and height before pregnancy). This calculator computes your BMI, places you in a category, and shows the matching IOM/ACOG total range and approximate weekly rate.
How much weight gain is normal in the first trimester?: First-trimester gain is usually small, often around 1–4 lb total, with most weight gained in the second and third trimesters at a steadier weekly pace.
Should I gain more weight if I'm having twins?: Yes, twin pregnancies have higher recommended ranges (for example, about 37–54 lb at a normal pre-pregnancy BMI). Specific guidance, especially for the underweight category, should come from your provider.
Is it safe to try to lose weight while pregnant?: You should not try to lose weight or restrict gestational weight gain to diet during pregnancy without medical supervision, even if you started at a higher weight. Talk to your provider about a healthy plan for you.

Keep reading

Sources: ACOG — Weight Gain During Pregnancy · CDC — Weight Gain During Pregnancy · Institute of Medicine (2009), Weight Gain During Pregnancy: Reexamining the Guidelines (NIH/NCBI) · MedlinePlus (NIH) — Pregnancy and Nutrition.