Pregnancy Weight Gain Calculator Online
Estimate a healthy pregnancy weight-gain range from your pre-pregnancy BMI, right in your browser. A general estimate, not medical advice.
The Pregnancy Weight Gain Calculator runs entirely in your browser. The weight, height, and week you enter never leave your device and nothing is uploaded to ArrayKit. Results are a general estimate, not medical advice.
Open the Pregnancy Calculator
About Pregnancy Weight Gain Calculator
Pregnancy Weight Gain Calculator estimates a healthy total weight-gain range for your pregnancy from your pre-pregnancy weight, height, and BMI category, using the Institute of Medicine (IOM) guidelines. Enter your current week and it also shows the gain typically expected by that point, interpolated across the pregnancy so early weeks call for less and later weeks for more. Switch between Metric (kilograms and centimetres) and US (pounds and feet/inches) units, and toggle Twins for the higher range that applies to a twin pregnancy. It is a quick way to see whether your gain so far tracks with a standard range before a prenatal visit or when planning meals and activity with your care team. Everything computes on your device — your weight, height, and week are never uploaded. This is a general estimate from a standard formula, not medical advice.
Features
- Calculates pre-pregnancy BMI from your weight and height
- Classifies BMI into the underweight, normal, overweight, or obese category the IOM guidelines use
- Shows the IOM total recommended weight-gain range for your BMI category
- Estimates the gain typically expected by your current week, not just the full-term total
- Twins toggle switches to the higher IOM range for a twin pregnancy
- Toggle between Metric (kg/cm) and US (lb/ft-in) units
- Copy a plain-text summary of your BMI, category, and gain ranges in one click
- Runs entirely in your browser — your figures never leave your device
How to use the Pregnancy Weight Gain Calculator
- Choose Metric or US units
- Enter your pre-pregnancy weight and height
- Enter your current week of pregnancy, and toggle Twins if it applies
- Read your BMI category, total recommended gain, and expected gain so far
Example
Input
normal BMI, week 20
Output
Total gain: 11.5–16 kg
A pre-pregnancy BMI in the Normal band uses the IOM 11.5–16 kg total-gain range for a singleton pregnancy.
Common errors & troubleshooting
- Pregnancy Weight Gain Calculator shows an error even though numbers were entered. — Make sure pre-pregnancy weight and height are both greater than zero, and the current week is between 0 and 45.
- Expected gain by week seems too low early in the pregnancy. — That is expected — the IOM curve allocates only a small share of the total range to the first trimester, with most of the gain spread across the second and third trimesters.
- Twin range looks the same as a singleton pregnancy. — Confirm the Twins toggle is switched on — it swaps in the higher IOM range for a twin pregnancy in the same BMI category.
- Result looks way too high or too low after switching units. — Switching between Metric and US keeps each unit's fields separate, so re-enter your weight and height in the newly selected unit system.
Frequently asked questions
- What guidelines does the Pregnancy Weight Gain Calculator use?
- It uses the Institute of Medicine (IOM, 2009) total pregnancy weight-gain ranges, which are keyed off your pre-pregnancy BMI category: underweight, normal, overweight, or obese.
- How does the Pregnancy Weight Gain Calculator estimate gain 'so far'?
- It interpolates the IOM total range across the pregnancy: roughly 10% of the range by the end of the first trimester (week 13), with the rest spread out linearly to full term (week 40).
- Does the Pregnancy Weight Gain Calculator support twin pregnancies?
- Yes. Turning on the Twins toggle switches to the higher IOM-based range published for a twin pregnancy in your same pre-pregnancy BMI category.
- Is the Pregnancy Weight Gain Calculator's result medical advice?
- No. It gives a general estimate from a standard formula and guideline table. It is not a diagnosis or a personalized plan — talk to your doctor or midwife about the weight gain that is right for you.
- Does the Pregnancy Weight Gain Calculator work in pounds and inches?
- Yes. Switch the unit toggle to US and enter your weight in pounds and your height in feet and inches — the calculator converts everything to metric internally before computing your BMI and gain ranges.
- Is my weight and week data uploaded when I use the Pregnancy Weight Gain Calculator?
- No. The Pregnancy Weight Gain Calculator runs entirely in your browser. The numbers you type are used only to compute the result on your device and are never sent to ArrayKit or anywhere else.
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