Pregnancy Weight Gain Calculator
Set a pregnancy weight-gain target range using your pre-pregnancy BMI
Pregnancy weight gain FAQ
Why does pre-pregnancy BMI matter for weight gain targets?
Most pregnancy weight-gain guidelines set different ranges based on body mass index (BMI) before pregnancy. The idea is to support fetal growth and maternal health while avoiding too little or too much gain on average.
Does “recommended range” mean I should diet or restrict?
Not automatically. Pregnancy needs enough nutrition for you and your baby. If your gain is outside the range, it’s usually a signal to talk with your prenatal team about symptoms, appetite, activity, and whether anything medical is going on. Avoid weight-loss dieting unless your clinician explicitly guides it.
What if my weight gain isn’t steady week to week?
That’s common. Nausea, constipation, hydration, clothing, and timing of weigh-ins can shift the scale. This calculator’s “pace needed” is an average, not a promise of how the scale should move each week.
Can I use this for twins?
Yes—this tool includes a twins option using commonly cited guideline ranges. For triplets or more, or if your pregnancy is high-risk, targets should be individualized by your clinician.
What counts as “pre-pregnancy weight” if I’m not sure?
Use your best estimate from just before pregnancy (for example, a recent clinic or home scale weight). If your first prenatal visit weight is early in pregnancy, some clinicians use that as a practical proxy.
How to use this pregnancy weight gain calculator
This tool estimates a recommended total pregnancy weight gain range using your pre-pregnancy BMI and whether you’re carrying one baby or twins. It also compares your gain so far (current minus pre-pregnancy weight) to that range and shows an average weekly pace that would get you to the target by week 40.
1) Enter height and choose units
Pick US units (lb, ft/in) or metric (kg, cm). Height is used to compute BMI, which places you into one of the standard guideline bands.
2) Add pre-pregnancy and current weight
Use your best pre-pregnancy estimate and a recent current weight. Try to weigh at a similar time of day.
3) (Optional) Add your current week
Weeks pregnant lets the calculator estimate how much time is left until week 40 and compute an average pace needed. Real patterns vary by trimester and symptoms.
What to do with the result
- If you’re within the range, treat it as a helpful check-in.
- If you’re below, mention it to your prenatal team—especially with severe nausea or weight loss.
- If you’re above, ask about nutrition quality, swelling, and safe activity guidance.
How the pregnancy weight gain math works
The calculator computes your pre-pregnancy BMI, selects a recommended total gain range for singleton or twins, then compares your gain so far to that range.
1) Calculate pre-pregnancy BMI
BMI is calculated from pre-pregnancy weight and height: BMI = kg ÷ m². US inputs are converted internally.
2) Apply guideline total gain ranges
The tool uses commonly cited guideline ranges by BMI category and pregnancy type, shown in lb or kg.
3) Compare gain so far
Gain so far = current weight − pre-pregnancy weight. Remaining is shown relative to the lower and upper ends of the recommended range.
4) Average weekly pace (optional)
If weeks pregnant is entered, the tool estimates weeks left to week 40 and computes an average: pace ≈ remaining gain ÷ weeks left.
References and further reading on pregnancy weight gain