Pregnancy health
Pregnancy Weight Gain Calculator
How much weight gain is expected at your week? Enter your pre-pregnancy height and weight, your current week, and your weight today to see your IOM/NAM target range — the guideline ACOG uses — and where you sit against it, for one baby or twins. Everything is computed on your own device: nothing is sent or saved.
These ranges are a guide, not a grade — where you sit is a conversation starter for your prenatal visits, never a verdict.
Pregnancy weight gain calculator
Based on the IOM/NAM 2009 gestational weight-gain guidelines as adopted by ACOG. The ranges are a guide, not a grade: single weigh-ins wobble, patterns matter, and where you sit is something to talk through at a prenatal visit — never a verdict, and never a reason to diet during pregnancy on your own.
How it works
The guideline behind the ranges
The recommended gain for a pregnancy depends on one thing: your pre-pregnancy BMI (weight in pounds × 703 ÷ height in inches², the standard formula). The Institute of Medicine — now the National Academy of Medicine — set the ranges in its 2009 guidelines after reviewing how gain related to outcomes on both sides, and ACOG adopted them as the working standard for prenatal care in the US. Lower starting BMI, higher recommended gain; higher starting BMI, lower recommended gain.
The pattern across the weeks matters too. The guidelines expect only about 1–4.5 lb across the whole first trimester, whatever your BMI category — then a steadier weekly gain through the second and third trimesters at a rate that also depends on the category (roughly 1 lb per week at the lower BMIs, about 0.6 at overweight, about 0.5 in the obesity range). To estimate the typical range at your week, this tool anchors the first trimester at 1–4.5 lb and adds the guideline weekly rate for each week after 13. Twin targets are published as whole-pregnancy totals only, so the twin week-band is a straight-line estimate toward that total.
| Pre-pregnancy BMI | Total gain, one baby | Weekly rate, 2nd–3rd trimester | Total gain, twins |
|---|---|---|---|
| Underweight (below 18.5) | 28–40 lb | 1–1.3 lb/week | No range established |
| Normal weight (18.5–24.9) | 25–35 lb | 0.8–1 lb/week | 37–54 lb (provisional) |
| Overweight (25–29.9) | 15–25 lb | 0.5–0.7 lb/week | 31–50 lb (provisional) |
| Obesity range (30 and above) | 11–20 lb | 0.4–0.6 lb/week | 25–42 lb (provisional) |
Two honest caveats. The ranges describe populations, and your provider may personalize yours — theirs is always the version to follow. And the weekly-rate math and the whole-pregnancy totals are separate guideline numbers, so the week-band and the total won't align to the pound; that's a property of the guidelines themselves, not an error in your tracking.
Read this before you weigh in
A range is a guide, not a grade
The bands exist because research links the overall pattern of gain — in either direction — to outcomes across large populations: gaining well under the band is associated with smaller babies and preterm birth, and gaining well over it with larger babies, cesarean delivery, and weight that's harder to shift afterward. But those are statistical associations across thousands of pregnancies, not predictions about yours, and plenty of healthy pregnancies spend time outside the band. A number outside the range means one thing: it's worth a conversation at your next prenatal visit. Not a problem to fix alone, and specifically not a reason to diet — ACOG does not recommend trying to lose weight during pregnancy.
And if weighing is a loaded subject for you — because of a past or present eating disorder, or just a difficult history with the scale — you're far from alone, and prenatal care can flex around it. It's routine to ask your care team to handle weigh-ins quietly, without reading the number aloud, and to track the pattern for you. Tell them it's a sensitive area; that's exactly the kind of thing they'd rather know.
Next steps
Related tools
Pregnancy week by week
What's developing at your week — and what your body is doing alongside the scale.
Prenatal visit schedule
Every visit, screen, and test on the standard timeline — including the weigh-ins.
How far along am I?
Pin down your current week first — the band on this page depends on it.
All pregnancy tools
The full suite — from timing conception to dating a pregnancy.
Sources
Where this comes from
Every number on this page is from the IOM/NAM 2009 gestational weight-gain guidelines as adopted by ACOG: the BMI-based total ranges, the first-trimester anchor, the second- and third-trimester weekly rates, and the provisional twin totals. The nutrition and activity basics (the ~340 and ~450 extra daily calories, the ~150 weekly minutes of moderate activity) are ACOG's. We apply their numbers; we don't invent our own — and the range that counts for your care is the one your provider sets with you.
Medically Reviewed & Fact-Checked · Updated
Reviewed by EasySTD Editorial Team
Compiled and checked by EasySTD's editorial team against CDC and public-health sources. This is educational information, not a substitute for advice from a licensed clinician. Our editorial guidelines →
3 Sources
Data & references
- IOM/NAM 2009: Weight Gain During Pregnancy — Reexamining the Guidelineshttps://nap.nationalacademies.org/catalog/12584/weight-gain-during-pregnancy-reexamining-the-guidelines
- ACOG Committee Opinion 548: Weight Gain During Pregnancyhttps://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2013/01/weight-gain-during-pregnancy
- CDC: Weight Gain During Pregnancyhttps://www.cdc.gov/maternal-infant-health/pregnancy-weight/index.html
EasySTD is an information and comparison directory, not a healthcare provider. This tool is general information based on published guidelines: it is not medical advice, a diagnosis, or an eating plan, and it does not create a doctor-patient relationship. Weight gain in pregnancy is interpreted by your prenatal care team across visits — bring questions about your pattern to them, and never start a diet during pregnancy without their guidance.
Good to Know
Pregnancy weight gain: frequently asked questions
How much gain the guidelines expect, what an out-of-band number does and doesn't mean, the first trimester, twins, and whether you really need to eat for two.
How much weight should I gain during pregnancy?
It depends on where you started. The IOM/NAM guidelines — the ones ACOG uses — set the target by your pre-pregnancy BMI: 28 to 40 pounds if your BMI was under 18.5, 25 to 35 pounds for a BMI of 18.5 to 24.9, 15 to 25 pounds for a BMI of 25 to 29.9, and 11 to 20 pounds for a BMI of 30 or above. These are ranges, not targets to hit exactly, and they describe the whole pregnancy — most of the gain comes in the second and third trimesters. Your provider may personalize the range for your situation, which is always the version to follow.
I'm above (or below) the range for my week — is something wrong?
Not necessarily, and it's genuinely not a grade. Single weigh-ins wobble with fluid, time of day, clothing, and the scale itself, and plenty of healthy pregnancies spend stretches outside the band — early nausea pulls many people under it, and fluid shifts push others over. What the research links to outcomes is the overall pattern, which is why the honest read on an out-of-band number is 'worth a conversation at your next prenatal visit,' not a problem to fix on your own. Your provider can look at the trend across visits, check for simple explanations, and adjust the plan with you. What ACOG specifically doesn't recommend is dieting or trying to lose weight during pregnancy.
How much should I gain in the first trimester?
Very little — the guideline expectation is only about 1 to 4.5 pounds across the entire first trimester, regardless of BMI category, because the baby is still tiny and your body is just beginning to build up blood volume and other supports. No extra calories are needed in these weeks. Many people gain nothing at all, and some lose a little to nausea — usually not a concern, though if you're struggling to keep food or fluids down, tell your provider, since that's treatable. The steadier weekly gain starts in the second trimester.
How do the ranges change with twins?
The twin ranges are higher and are described by the IOM/NAM as provisional, because less data exists: 37 to 54 pounds if your pre-pregnancy BMI was in the normal range, 31 to 50 pounds if it was 25 to 29.9, and 25 to 42 pounds if it was 30 or above. No twin range was set for the underweight category at all — there simply wasn't enough evidence — so that combination is one to plan directly with your provider. The guidelines also give the twin targets as whole-pregnancy totals only, so any week-by-week twin band (including the one in this tool) is an estimate stretched across the pregnancy rather than a published weekly rate.
Do I really need to 'eat for two'?
No — that phrase overshoots by a lot. Per ACOG, a singleton pregnancy needs roughly no extra calories in the first trimester, about 340 extra per day in the second, and about 450 extra per day in the third — closer to an extra snack than an extra meal. Beyond that, the basics are ordinary ones: regular balanced meals, a daily prenatal vitamin, and around 150 minutes a week of moderate activity like brisk walking if your provider has cleared it. Anything more tailored than that — specific eating plans, calorie targets, or changes for a medical condition — belongs with your provider or a dietitian, not a calculator.
Is what I enter here private?
Yes. This calculator runs entirely in your browser: your height, weights, and week are computed on your own device and are never sent to a server, stored, or shared — close the tab and they're gone. In a post-Dobbs world we treat reproductive health data as sensitive by default, and the safest data is data that never leaves your device. What you see here is general educational math based on the published IOM/NAM guidelines; it isn't medical advice, a diagnosis, or a substitute for your prenatal care team.
Have a different question? Browse the full pregnancy FAQ library, every question we answer, in one place.