ALPPI FIT LAB
Pregnancy Weight Gain Calculator
Use this pregnancy weight gain calculator to see how much weight is healthy for you to gain, based on your pre-pregnancy BMI. You'll get your total goal, the range for your current week, and a chart of your progress, for one baby or twins.
- IOM / ACOG guidelines
- Week-by-week chart
- Twins supported
How Much Weight Should I Gain?
Your personal range based on pre-pregnancy BMI
Enter your height and weights, then tap Check my weight gain.
Key takeaways
- Healthy pregnancy weight gain depends on your pre-pregnancy BMI: 25–35 lb at a healthy weight, less if overweight, more if underweight.
- Most people gain only 1.1–4.4 lb in the first trimester, then about 0.5–1 lb a week.
- Twins need more: 37–54 lb for a healthy pre-pregnancy BMI.
- Don't diet during pregnancy. If you're outside the range, talk with your provider about a plan.
How to use the pregnancy weight gain calculator
- Choose your units, US (pounds, feet and inches) or metric (kilograms, centimeters).
- Enter your height and pre-pregnancy weight. We use them to work out your body mass index (BMI), which sets your recommended range.
- Enter your current weight and week of pregnancy. Tick the twins box if you're expecting two.
- See where you are. You'll get your total goal, the healthy range for this exact week, how much is left to gain, and a chart of your progress.
How much weight should I gain during pregnancy?
Recommended pregnancy weight gain depends on your BMI before pregnancy. These are the Institute of Medicine (IOM) 2009 guidelines, which ACOG and the CDC use:
| Pre-pregnancy BMI | Total gain: one baby | Weekly gain, 2nd & 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 |
| Healthy weight (18.5–24.9) | 25–35 lb (11.5–16 kg) | 0.8–1 lb (0.35–0.50 kg) | 37–54 lb (17–25 kg) |
| Overweight (25.0–29.9) | 15–25 lb (7–11.5 kg) | 0.5–0.7 lb (0.23–0.33 kg) | 31–50 lb (14–23 kg) |
| Obesity (30 or higher) | 11–20 lb (5–9 kg) | 0.4–0.6 lb (0.17–0.27 kg) | 25–42 lb (11–19 kg) |
Source: Institute of Medicine (2009), Weight Gain During Pregnancy: Reexamining the Guidelines. Twin ranges are provisional. Weekly rates assume about 1.1–4.4 lb (0.5–2 kg) gained in the first trimester.
How the calculator works
First, we calculate your pre-pregnancy BMI:
or BMI = 703 × weight (lb) ÷ height (in)²
Your BMI group sets your total target. To get a range for your exact week, we follow the IOM's assumptions. Weight gain in the first 13 weeks is small, about 1.1 to 4.4 lb in total. After that, gain climbs at a steady rate until you reach your total target at 40 weeks. If your gain falls inside the shaded band on the chart, you're on track.
Example: At 5'5" and 140 lb before pregnancy, your BMI is 23.3 (healthy weight). The goal is 25–35 lb in total, and at 20 weeks a healthy range is about 7.3 to 12.3 lb.
Where does pregnancy weight go?
Only part of pregnancy weight is your baby. For a healthy-weight pregnancy with one baby, the extra pounds are roughly split like this:
| Where it goes | Approximate weight |
|---|---|
| Baby | 7–8 lb (3.2–3.6 kg) |
| Larger breasts | 1–3 lb (0.5–1.4 kg) |
| Larger uterus | 2 lb (0.9 kg) |
| Placenta | 1.5 lb (0.7 kg) |
| Amniotic fluid | 2 lb (0.9 kg) |
| Increased blood volume | 3–4 lb (1.4–1.8 kg) |
| Increased fluid volume | 2–3 lb (0.9–1.4 kg) |
| Fat stores (energy for birth and breastfeeding) | 6–8 lb (2.7–3.6 kg) |
Source: Mayo Clinic, Pregnancy weight gain: What's healthy?
Tips for healthy pregnancy weight gain
- You're not really "eating for two." ACOG suggests no extra calories in the first trimester, about 340 extra a day in the second, and about 450 extra a day in the third, for one baby.
- Choose nutrient-dense foods: vegetables, fruit, whole grains, lean protein, beans, dairy or fortified alternatives, and healthy fats.
- Take a prenatal vitamin with folic acid, iron and iodine, as your provider recommends.
- Stay active. Most people can do at least 150 minutes of moderate activity a week, such as walking or swimming, with their provider's OK.
- Weigh yourself at the same time each week. Day-to-day changes are mostly water.
- Don't diet during pregnancy unless your provider gives you a plan, even if you're above the range.
Call your provider if you gain weight suddenly (for example, more than 2 lb in a week in the third trimester), especially with swelling of the face or hands, headaches or vision changes. These can be signs of preeclampsia.
Frequently asked questions
How much weight should I gain during pregnancy?
It depends on your pre-pregnancy BMI. With one baby, the IOM recommends 28–40 lb if underweight, 25–35 lb at a healthy weight, 15–25 lb if overweight, and 11–20 lb with obesity.
How much weight should I gain with twins?
The IOM's provisional twin guidelines are 37–54 lb for a healthy pre-pregnancy BMI, 31–50 lb if overweight, and 25–42 lb with obesity. There's no official range for an underweight BMI, so ask your provider for a personal target.
How much weight should I gain in the first trimester?
Usually only about 1.1 to 4.4 lb (0.5 to 2 kg) in total over the first 13 weeks. Some people lose a little weight because of morning sickness, which is usually fine.
How much weight should I gain per week?
After the first trimester, with one baby: about 1–1.3 lb a week if underweight, 0.8–1 lb at a healthy weight, 0.5–0.7 lb if overweight, and 0.4–0.6 lb with obesity.
Is it bad to gain too much weight while pregnant?
Gaining well above the recommended range is linked to a higher chance of gestational diabetes, high blood pressure, a cesarean birth, a larger baby, and holding on to extra weight after birth. Talk to your provider before making changes, because dieting isn't recommended during pregnancy.
What if I'm not gaining enough weight during pregnancy?
Gaining less than recommended is linked to a higher chance of a small-for-gestational-age baby and preterm birth. Your provider may suggest more frequent meals, extra protein and healthy fats, or a referral to a dietitian.
Does this calculator work if I'm overweight or have obesity?
Yes. Recommended ranges are lower for higher BMIs, but some gain is still recommended. The calculator shows your personal range for each week.
How accurate is BMI during pregnancy?
BMI is calculated from your pre-pregnancy weight, because current weight includes the baby, placenta and fluid. It's a screening tool, and your provider may adjust your target based on your health.
Sources
- Institute of Medicine (2009). Weight Gain During Pregnancy: Reexamining the Guidelines (NCBI Bookshelf)
- ACOG Committee Opinion 548: Weight Gain During Pregnancy
- CDC: Weight Gain During Pregnancy
- Mayo Clinic: Pregnancy weight gain: What's healthy?
- ACOG: How much weight should I gain during pregnancy?
This calculator is for general information and is not medical advice. Your provider may recommend a different target based on your health, your pregnancy, or conditions such as diabetes or high blood pressure. Contact your provider about any sudden weight change, swelling or other concerns.
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