Pregnancy Weight Gain Calculator
Track healthy pregnancy weight gain based on pre-pregnancy BMI.
This pregnancy weight gain calculator (a pregnancy weight gain estimator) checks your current weight gain against recommended healthy pregnancy weight ranges, which vary based on your pre-pregnancy BMI and how far along you are.
Enter your pre-pregnancy weight, current weight, and week of pregnancy, and the calculator compares your gain against the recommended range.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| Normal pre-pregnancy BMI, 20 weeks pregnant | Full-term target: 25-35 lbs · Expected so far: roughly 10-15 lbs | Guidelines suggest minimal gain in the first trimester followed by roughly 1 lb/week afterward for a normal pre-pregnancy BMI - by the halfway point, total gain in the 10-15 lb range is a commonly cited pace toward the 25-35 lb full-term target. |
| Overweight pre-pregnancy BMI, 30 weeks pregnant | Full-term target: 15-25 lbs · Expected so far: roughly 10-18 lbs | The overweight category has a lower full-term target and a slower recommended weekly pace than the normal-BMI category, so a smaller cumulative gain by the same week of pregnancy is expected and appropriate. |
Recommended Weight Gain Ranges by BMI
Guidelines commonly recommend total pregnancy weight gain based on pre-pregnancy BMI category: roughly 28-40 lbs for underweight, 25-35 lbs for normal weight, 15-25 lbs for overweight, and 11-20 lbs for obese pre-pregnancy BMI categories, for a single pregnancy.
Why Gain Is Not Linear Throughout Pregnancy
Most weight gain guidance recommends a smaller amount in the first trimester (often just 1-4 lbs total) and a steadier weekly gain in the second and third trimesters, rather than an even amount spread across all nine months.
How to Use the Pregnancy Weight Gain Calculator
- Open the Pregnancy Weight Gain Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the pregnancy weight gain calculator works.
Frequently Asked Questions
How is a calculator for weight gain during pregnancy used?
It compares your actual weight gain at a given week of pregnancy against a recommended range based on your pre-pregnancy BMI category.
What is a healthy pregnancy weight gain range?
It varies by pre-pregnancy BMI: roughly 25-35 lbs for normal weight, 15-25 lbs for overweight, and 11-20 lbs for obese categories, for a single pregnancy.
Is weight gain the same every week of pregnancy?
No, most guidance recommends minimal gain in the first trimester followed by a steadier weekly rate in the second and third trimesters.
How do I use this pregnancy weight gain calculator?
Enter the known values, review the units or settings, and the calculator updates the result instantly. The formula and example on this page show how the answer is produced.
What does the Pregnancy Weight Gain Calculator calculate?
Track healthy pregnancy weight gain based on pre-pregnancy BMI. It is designed for fast browser-based calculations without sign-up, downloads, or manual spreadsheet setup.
What formula does this pregnancy weight gain use?
The formula is: Recommended Range ≈ f(Pre-Pregnancy BMI Category, Week of Pregnancy). Current recommended pregnancy weight gain ranges come from the US National Academy of Medicine (formerly the Institute of Medicine), most recently updated in 2009 guidelines that, for the first time, tied recommended gain ranges to a mother's pre-pregnancy BMI category - replacing older, one-size-fits-all recommendations after research found that appropriate weight gain varies significantly depending on starting body weight.
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Last updated: September 27, 2026.