Pregnancy Weight Gain Calculator
Calculate prepregnancy BMI, current weight gain, the total pregnancy gain range associated with that BMI, and the corresponding end-of-pregnancy weight range for one baby or twins.
This calculator does not judge whether your gain is appropriate for the current week. Weight gain is not linear, and individual goals can differ. Use the result as a discussion aid with your prenatal care professional—not as a diet, treatment or diagnosis.
How the calculator works
- It converts height and prepregnancy weight to metric units and calculates BMI = weight in kg ÷ height in metres².
- It maps the BMI to the CDC categories: underweight below 18.5, normal weight 18.5–24.9, overweight 25.0–29.9 and obesity at 30 or above.
- It selects the CDC total pregnancy weight-gain range for one baby or twins.
- It subtracts prepregnancy weight from current weight and shows how much gain remains to each end of the total range.
The current week labels the trimester only. The page deliberately does not divide the total range evenly by week because pregnancy weight gain is not linear and the CDC provides separate tracking charts for discussing progress with a clinician.
CDC total weight-gain ranges used
| Prepregnancy BMI | One baby | Twins |
|---|---|---|
| Underweight: below 18.5 | 28–40 lb (12.7–18.1 kg) | 50–62 lb (22.7–28.1 kg) |
| Normal: 18.5–24.9 | 25–35 lb (11.3–15.9 kg) | 37–54 lb (16.8–24.5 kg) |
| Overweight: 25.0–29.9 | 15–25 lb (6.8–11.3 kg) | 31–50 lb (14.1–22.7 kg) |
| Obesity: 30 or above | 11–20 lb (5.0–9.1 kg) | 25–42 lb (11.3–19.1 kg) |
The CDC notes that the underweight-twin recommendation comes from a cited twin-pregnancy study rather than the Institute of Medicine recommendation set. Triplet and higher-order pregnancies need individualized advice.
Checked examples
| Inputs | Prepregnancy BMI | Total gain range | Current and final weights |
|---|---|---|---|
| One baby; 165 cm; 60 kg before; 67 kg now | 22.04 — normal | 11.34–15.88 kg | 7.00 kg gained; 71.34–75.88 kg final range |
| One baby; 64 in; 180 lb before; 190 lb now | 30.90 — obesity | 11–20 lb | 10 lb gained; 191–200 lb final range |
| Twins; 170 cm; 70 kg before; 80 kg now | 24.22 — normal | 16.78–24.49 kg | 10.00 kg gained; 86.78–94.49 kg final range |
Use and safety limits
- The range is based on prepregnancy BMI, not BMI during pregnancy. BMI is a screening category and does not measure body composition.
- Do not try to lose weight, restrict food or accelerate weight gain during pregnancy based on this page. Your clinician can account for fetal growth, fluid, nausea, diabetes, blood pressure, prior surgery and other medical factors.
- Current gain below or above the final range is not a week-specific diagnosis. The result cannot determine fetal growth or pregnancy health.
- Sudden weight change, severe swelling, severe headache, vision changes, persistent vomiting or any urgent symptom needs prompt professional assessment.
Primary sources
- CDC: Weight Gain During Pregnancy — BMI categories, singleton and twin total ranges, tracking resources and clinical context.
- National Academies: Weight Gain During Pregnancy—Reexamining the Guidelines — 2009 consensus report underlying the recommendations.
Related calculators: Due Date Calculator, BMI Calculator, Ovulation Calculator and Calorie Calculator.
Questions
Does this give a target for my current week?
No. It shows the full-pregnancy range associated with prepregnancy BMI. Weight does not rise uniformly every week, so progress should be reviewed with the prenatal care team and an appropriate tracking chart.
Which weight should I use for BMI?
Use weight immediately before pregnancy, not current pregnancy weight. If that value is unknown, ask the clinician what documented baseline to use.
Can I use it for triplets?
No. The CDC advises people pregnant with triplets or more to discuss individualized weight-gain goals with their health care provider.
What if current weight is below prepregnancy weight?
The calculator shows a negative change rather than hiding it. Vomiting, inability to keep fluids down, rapid loss or concern about nutrition should be discussed promptly with a clinician.