Pregnancy Weight Gain Calculator
See your recommended pregnancy weight gain by week using IOM guidelines and your pre-pregnancy BMI.
Recommended total gain: —
Where your gain sits this week
Personalised guidance
How to use the Pregnancy Weight Gain Calculator
Step 1 — Enter your dates
- Add the requested dates and details.
Step 2 — See your results
- Key dates and a visual timeline update instantly.
Step 3 — Explore
- Review the breakdown, schedule and guidance.
Step 4 — Export
- Download a PDF to share with your provider.
Frequently asked questions
It depends on your pre-pregnancy BMI. The IOM guidelines suggest about 11.5–16 kg for a normal-weight start, 12.5–18 kg if underweight, 7–11.5 kg if overweight and 5–9 kg if obese, with higher ranges for twins.
Most gain happens after the first trimester. The tool adds a small first-trimester gain (about 0.5–2 kg) to a steady weekly rate for your BMI category to estimate a healthy range by your current week.
No. A lower recommended range is normal for a higher starting BMI, but it is not a weight-loss plan. Do not actively diet to lose weight in pregnancy unless your doctor specifically advises it.
Twin pregnancies need more gain — roughly 16.8–24.5 kg for a normal-weight start — and the evidence is less precise, so your obstetrician’s individual target matters most.
Being a little above or below is common and not automatically a problem; the trend matters more than one reading. Persistent large deviations are worth discussing with your provider. This tool gives general information for education, not medical advice; always follow your midwife, doctor or other qualified healthcare professional.
About the Pregnancy Weight Gain Calculator
This tool shows how much weight gain is healthy during your pregnancy, tailored to your pre-pregnancy BMI, and lets you check whether your gain so far is on track for how many weeks along you are. It follows the U.S. Institute of Medicine (now National Academy of Medicine) guidelines, the standard used in antenatal care.
Why pre-pregnancy BMI sets the target
There is no single right number. The healthy range depends on where you started: someone underweight before pregnancy is advised to gain more, and someone who started overweight or obese is advised to gain less — not as a diet, but because that pattern is linked to the best outcomes for parent and baby. The tool calculates your pre-pregnancy BMI, places you in a category, and shows the matching total range, with the wider ranges used for twin pregnancies.
Tracking by week, sensibly
Because most gain happens in the second and third trimesters, a single total is not that useful mid-pregnancy. So the tool estimates a healthy range for your current week — a modest first-trimester gain plus a steady weekly rate for your category — and, if you enter your current weight, tells you whether you are below, within or above that range. Weight in pregnancy is not linear and fluctuates week to week, so the trend matters far more than any single weigh-in.
Guidance, not a rule
These are population guidelines, not a personal prescription; healthy pregnancies gain at different rates, and conditions like gestational diabetes change the picture. This tool gives general information for education, not medical advice; always follow your midwife, doctor or other qualified healthcare professional. Bring the downloadable report to your appointments and let your provider set your individual target.