See your recommended pregnancy weight gain based on the Institute of Medicine guidelines — your total range, how much to gain by this week, and whether you're on track.
Good to know: These are IOM population guidelines, not a target for every person. Your provider personalizes the right goal for you. Everything runs in your browser — nothing you enter is stored or sent anywhere.
Gaining weight in pregnancy is not just normal — it's necessary. The weight you put on supports your growing baby, builds the placenta, expands your blood volume, and lays down the energy reserves your body draws on during birth and breastfeeding. So this isn't a number to fear or fight. It's a sign that your body is doing exactly what it's designed to do.
At the same time, research has taught us that both ends of the spectrum carry some risk. Gaining too little is linked to babies born smaller than expected and to preterm birth. Gaining too much is linked to larger babies, a higher chance of a cesarean birth, gestational diabetes, high blood pressure in pregnancy, and more weight retained after delivery. That's why the Institute of Medicine (now the National Academy of Medicine) published weight-gain ranges tuned to your starting body size — a gentle target zone rather than a single magic number.
The most important word in all of this is individualized. These ranges describe healthy averages across large populations. They don't account for your unique medical history, your baby's growth, or how you're feeling day to day. Your doctor or midwife weighs all of that together, which is why their guidance always comes first. Think of this calculator as a helpful map — not the final word.
The 2009 IOM/NAM guidelines base your recommended total gain on your pre-pregnancy body mass index (BMI) — your weight before pregnancy relative to your height. The lower your starting BMI, the more you're generally advised to gain, and vice versa. The table below shows the recommended ranges for a single baby, along with the typical weekly rate for the second and third trimesters.
| Pre-pregnancy BMI | Category | Total gain (lb) | Total gain (kg) | Weekly rate, 2nd/3rd tri |
|---|---|---|---|---|
| Below 18.5 | Underweight | 28–40 lb | 12.5–18 kg | ~1.0–1.3 lb (0.44–0.58 kg) |
| 18.5–24.9 | Normal weight | 25–35 lb | 11.5–16 kg | ~0.8–1.0 lb (0.35–0.50 kg) |
| 25.0–29.9 | Overweight | 15–25 lb | 7–11.5 kg | ~0.5–0.7 lb (0.23–0.33 kg) |
| 30.0 and above | Obese | 11–20 lb | 5–9 kg | ~0.4–0.6 lb (0.17–0.27 kg) |
Across the first trimester, all categories are expected to gain only a little — about 1.1–4.4 lb (0.5–2 kg) total — with the steadier weekly gain kicking in from around week 14. That's the logic this calculator uses to estimate how much you'd typically have gained by the week you entered.
It's reassuring to see that pregnancy weight is spread across many places — only a fraction of it is body fat. For a typical gain of around 30 lb, the approximate breakdown looks like this:
Seen this way, the number on the scale is really a collection of healthy, purposeful changes — most of which leave your body in the weeks and months after birth.
Weight gain isn't evenly spaced across pregnancy, and it isn't meant to be. In the first trimester, gain is usually minimal — often just a couple of pounds, and sometimes none at all if nausea is in the picture. Your baby is still tiny, so your body simply doesn't need much extra yet.
The second trimester is typically when gain becomes steady and noticeable. Appetite often returns, morning sickness eases, and your baby and placenta grow quickly. This is where the weekly rates in the table above come into play. The third trimester continues that steady climb, though many people find gain slows a little in the final weeks. Remember that weekly gain is naturally uneven — a big week followed by a flat one is completely ordinary. Look at the trend over several weeks rather than reacting to any single weigh-in.
Carrying twins means supporting two babies and a larger placenta, so recommended gain is higher. The IOM offers provisional total ranges for twins: 37–54 lb (16.8–24.5 kg) at a normal starting weight, 31–50 lb (14.1–22.7 kg) if overweight, and 25–42 lb (11.3–19.1 kg) with obesity. There is no established range for people who start underweight and are carrying twins, so if that's you, your provider will set a personal goal. Because the IOM did not publish weekly rates for twins, the calculator spreads the twin total evenly across pregnancy as a rough guide only.
Plenty of other situations call for tailored advice, too: a history of an eating disorder, bariatric surgery, diabetes, thyroid conditions, very short stature, or being an adolescent. In all of these, the standard ranges are a starting point at most — your care team is the right source for a goal that fits your circumstances.
Watching your body change so quickly can stir up complicated feelings, and that's okay. It helps to remember that weight is just one signal among many. A healthy pregnancy is built far more on nourishing food, gentle movement, rest, and regular prenatal care than on hitting an exact number on the scale. The IOM ranges exist to guide care, not to grade you.
If the number ever becomes a source of anxiety, you're allowed to ask your provider to weigh you facing away from the display, or to focus your visits on how you and your baby are doing overall. Be gentle with yourself. You're growing a whole new person — and doing it thoughtfully enough to read a page like this one. That care counts for a great deal.
It depends on your pre-pregnancy BMI. Using the Institute of Medicine (IOM/NAM) 2009 guidelines for a single baby, the total recommended gain is 28–40 lb (12.5–18 kg) if you were underweight, 25–35 lb (11.5–16 kg) if you were a normal weight, 15–25 lb (7–11.5 kg) if you were overweight, and 11–20 lb (5–9 kg) if you had obesity. These are population ranges — your provider may set a different, personalized target that is right for you.
Yes. Most people gain only about 1.1–4.4 lb (0.5–2 kg) across the entire first trimester, and some gain nothing at all — especially with nausea or morning sickness. The steadier, more noticeable gain usually starts in the second trimester as your baby and your body grow. If you ever lose a significant amount of weight or cannot keep food down, check in with your provider.
From about week 14 onward, a typical weekly rate for a single pregnancy is roughly 1.0–1.3 lb (0.44–0.58 kg) if you started underweight, 0.8–1.0 lb (0.35–0.50 kg) if you were a normal weight, 0.5–0.7 lb (0.23–0.33 kg) if you were overweight, and 0.4–0.6 lb (0.17–0.27 kg) if you had obesity. Weekly gain is rarely perfectly even, so look at the trend over a few weeks rather than any single reading.
The IOM gives provisional total-gain ranges for twins: 37–54 lb (16.8–24.5 kg) at a normal starting weight, 31–50 lb (14.1–22.7 kg) if overweight, and 25–42 lb (11.3–19.1 kg) with obesity. There is no specific published range for underweight people carrying twins, so if that's you, your provider will set an individual goal. Twin pregnancies are higher-risk overall, so provider-guided targets matter even more.
Try not to worry from a single number. The IOM ranges describe healthy averages for the general population, not a pass/fail test. Gaining a little outside the range for a week or two is common and usually fine. If your trend is consistently well above or below the recommended range, bring it up at your next visit — your provider can look at the whole picture, including your nutrition, activity, and your baby’s growth, and adjust guidance as needed.