Pregnancy Weight Gain Calculator
Use this pregnancy weight gain calculator to see a healthy range for your total gain and for this exact week, based on the Institute of Medicine guidelines that doctors use. It works for single and twin pregnancies, in pounds or kilograms, with a personal week-by-week chart.
- Based on IOM 2009 guidelines
- Range for every week
- Single or twins
- Free, private, no sign-up
Your BMI before pregnancy decides which range applies. Use your weight just before you became pregnant.
Recommended total gain
25–35 lb
by 40 weeks for a normal pre-pregnancy BMI
On track at week 20
Your weight gain chart
The green band is the healthy gain range for each week. The pink dot is you.
Week-by-week targets
Suggested gain and the matching weight range at key points in your pregnancy.
| Week | Gain from start | Your weight range |
|---|
A pregnancy weight gain calculator made for you
Many calculators only give one total for the whole pregnancy. This one tells you where you should be right now and shows it on a chart.
Trusted guidelines
Ranges follow the Institute of Medicine (now the National Academy of Medicine) 2009 guidelines, which ACOG and most doctors use.
A range for every week
See exactly how much gain is healthy at your current week, not just the total by delivery.
Twin pregnancies
Switch to twins for the separate IOM ranges recommended when you are carrying two babies.
Personal chart
A clear chart plots your gain against the healthy band for all 40 weeks.
Pounds or kilograms
Use lb and feet or kg and centimeters. Your values convert instantly when you switch.
Completely private
Nothing is stored or sent anywhere. All calculations happen in your browser.
How to use the pregnancy weight gain calculator
It takes less than a minute. Results update as you type.
- Choose your unitsPick pounds and feet, or kilograms and centimeters.
- Enter your height and pre-pregnancy weightThese set your BMI category, which decides your healthy range.
- Add your current weightOptional, but it lets the calculator tell you if you are on track.
- Set how many weeks pregnant you areType the week or drag the slider from 1 to 42.
- Choose one baby or twinsThen read your total range, this week's range, chart and week-by-week table.
How much weight should you gain during pregnancy?
The healthy amount depends on your body mass index (BMI) before pregnancy. 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 recommendations.
| Pre-pregnancy BMI | Total gain, one baby | Weekly, 2nd and 3rd trimester | Total gain, twins |
|---|---|---|---|
| Underweight (below 18.5) | 28–40 lb (12.5–18 kg) | 1–1.3 lb (0.44–0.58 kg) | No IOM guideline |
| Normal (18.5–24.9) | 25–35 lb (11.5–16 kg) | 0.8–1 lb (0.35–0.5 kg) | 37–54 lb (17–25 kg) |
| Overweight (25–29.9) | 15–25 lb (7–11.5 kg) | 0.5–0.7 lb (0.23–0.33 kg) | 31–50 lb (14–23 kg) |
| Obese (30 or more) | 11–20 lb (5–9 kg) | 0.4–0.6 lb (0.17–0.27 kg) | 25–42 lb (11–19 kg) |
Most people gain only 1.1 to 4.4 lb (0.5 to 2 kg) in the first trimester. Steadier gain follows in the second and third trimesters. You can check your starting BMI with the BMI calculator.
Week-by-week weight gain for a normal BMI
For a single pregnancy with a starting BMI between 18.5 and 24.9, a healthy gain looks roughly like this:
| Week | Total gain (lb) | Total gain (kg) |
|---|---|---|
| Week 4 | 0.3–1.4 lb | 0.2–0.6 kg |
| Week 8 | 0.7–2.7 lb | 0.3–1.2 kg |
| Week 12 | 1–4.1 lb | 0.5–1.8 kg |
| Week 13 | 1.1–4.4 lb | 0.5–2 kg |
| Week 16 | 3.8–7.8 lb | 1.7–3.6 kg |
| Week 20 | 7.3–12 lb | 3.4–5.6 kg |
| Week 24 | 11–17 lb | 5–7.7 kg |
| Week 28 | 14–21 lb | 6.6–9.8 kg |
| Week 32 | 18–26 lb | 8.2–12 kg |
| Week 36 | 21–30 lb | 9.9–14 kg |
| Week 40 | 25–35 lb | 12–16 kg |
Where does the pregnancy weight go?
A typical gain of around 30 lb (13.6 kg) is not all fat. Most of it supports your baby and your changing body.
| Where it goes | Approximate weight |
|---|---|
| Baby | 7.5 lb (3.4 kg) |
| Extra blood volume | 4 lb (1.8 kg) |
| Extra body fluids | 4 lb (1.8 kg) |
| Fat stores for birth and breastfeeding | 7 lb (3.2 kg) |
| Amniotic fluid | 2 lb (0.9 kg) |
| Larger uterus | 2 lb (0.9 kg) |
| Breast tissue | 2 lb (0.9 kg) |
| Placenta | 1.5 lb (0.7 kg) |
Tips for healthy weight gain
Most people do not need extra calories in the first trimester. ACOG suggests about 340 extra calories a day in the second trimester and about 450 in the third for a single pregnancy. Focus on protein, fruit, vegetables, whole grains and plenty of water, and stay active with exercise your provider approves. The protein calculator and water intake calculator can help with daily targets.
Why tracking pregnancy weight gain helps
Healthy gain supports a healthy pregnancy for you and your baby.
Peace of mind. Know that a few pounds up or down this week is normal and within range.
Better prenatal visits. Bring clear numbers and questions to your doctor or midwife.
Lower risks. Gaining within the guidelines is linked with fewer complications for mother and baby.
Plan ahead. See what is coming in each trimester so nothing feels like a surprise.
Easier recovery. Healthy gain can make returning to your usual weight after birth easier.
Built for twins too. Get ranges that match a twin pregnancy instead of guessing.
Pregnancy weight gain FAQs
Answers to common questions. Always follow the advice of your own provider.
It depends on your BMI before pregnancy. For one baby, the Institute of Medicine recommends 28 to 40 lb if you were underweight, 25 to 35 lb at a normal weight, 15 to 25 lb if overweight and 11 to 20 lb if obese.
Most people gain about 1.1 to 4.4 lb (0.5 to 2 kg) in total during the first trimester. Some lose a little because of morning sickness, which is usually fine, but tell your provider if you cannot keep food or fluids down.
In the second and third trimesters, the IOM suggests about 1 to 1.3 lb a week if you were underweight, 0.8 to 1 lb at a normal weight, 0.5 to 0.7 lb if overweight and 0.4 to 0.6 lb if obese.
For twins, the IOM recommends 37 to 54 lb for a normal BMI, 31 to 50 lb if overweight and 25 to 42 lb if obese. There is no official twin guideline for an underweight BMI, so ask your provider for a personal target.
For a single pregnancy with a normal starting BMI, a gain of roughly 7 to 12 lb (3.3 to 5.6 kg) by week 20 is within the healthy range. Enter your own details above for a personal range.
Yes, a small loss in the first trimester is common because of nausea and food aversions. Most people start gaining steadily in the second trimester. Contact your provider if you are vomiting often or losing weight quickly.
Small differences from week to week are normal. If your gain stays well above or below the range, talk to your doctor or midwife before changing your diet. Dieting to lose weight is not recommended during pregnancy.
A typical 30 lb gain includes about 7.5 lb for the baby, 7 lb of fat stores, 4 lb of extra blood, 4 lb of extra fluids and around 2 lb each for amniotic fluid, the uterus and breast tissue, plus 1.5 lb for the placenta.
No. It applies the published IOM guidelines to the numbers you enter, which is a useful guide but not a diagnosis. Your doctor or midwife may set a different target based on your health and pregnancy.
See your healthy range for this week
Enter your height, weight and week to get a personal range, chart and week-by-week targets in seconds.
For general information only, not medical advice. Ranges are based on the Institute of Medicine 2009 guidelines and may not suit every pregnancy. Always follow the advice of your doctor or midwife.