Pregnancy Weight Gain CalculatorFree online fitness & health calculator — instant results, no sign-up
Recommended weight gain by pre-pregnancy BMI.
For general information only. This is not medical advice, diagnosis, dosing guidance or a treatment recommendation. Talk to a doctor or other qualified health professional about your health, pregnancy, or diet.
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About the Pregnancy Weight Gain Calculator
The Pregnancy Weight Gain Calculator estimates recommended total weight gain throughout pregnancy based on your pre-pregnancy body mass index (BMI). It provides target weight ranges for both singleton and twin pregnancies according to standard clinical weight guidelines.
- Height
- Maternal height in centimeters (typically between 120 and 220 cm).
- Pre-pregnancy weight
- Body weight immediately prior to pregnancy in kilograms (typically between 30 and 250 kg).
- Twins
- Indicates whether you are carrying a singleton (No) or twin pregnancy (Yes).
Formula and method
BMI = w / (h / 100)^2
- BMIPre-pregnancy body mass index in kg/m²
- wPre-pregnancy weight in kilograms
- hHeight in centimeters
The tool divides pre-pregnancy weight by height in meters squared to find your baseline BMI, rounded to one decimal place. It then assigns a target weight gain bracket based on whether BMI is underweight (< 18.5), normal weight (18.5–24.9), overweight (25.0–29.9), or obese (≥ 30.0), adjusting for singleton versus twin gestations.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Height175 cm
- Pre-pregnancy weight62 kg
- TwinsNo
Results
- Pre-pregnancy BMI20.2
- Recommended total gain11.5 – 16 kg
How to use the Pregnancy Weight Gain Calculator
- 1Convert height from centimeters to meters by dividing by 100.
- 2Calculate baseline BMI by dividing pre-pregnancy weight by the square of height in meters.
- 3Categorize the BMI into underweight (<18.5), normal (18.5–24.9), overweight (25.0–29.9), or obese (≥30.0).
- 4Match the BMI tier and pregnancy type (singleton or twins) to the established total recommended weight gain range.
Reading your result
The primary result shows your baseline BMI alongside the target total gestational weight gain. Staying within your recommended range supports fetal development while lowering risks of gestational diabetes, preeclampsia, and cesarean delivery.
Limitations
This calculator provides broad population-level target ranges and does not account for trimester-by-trimester pacing, fluid retention, higher-order multiples (triplets or more), or individualized clinical factors. Always consult your obstetric healthcare provider for personalized targets.
Common questions
Why is the recommended gain for twins with a BMI under 18.5 listed as 'Not established'?+
Clinical guidelines from health organizations do not have sufficient population data to set a standardized, safe target range for underweight mothers expecting twins; your obstetrician will provide a personalized target.
Does this calculator show weight gain by trimester?+
No, this calculator only determines the recommended total weight gain across the entire pregnancy from conception to delivery.
What happens if I gain more or less weight than recommended?+
Gaining outside the target range can happen due to fluid shifts, genetics, or appetite variations; discuss your weight trajectory with your healthcare provider rather than attempting unsupervised dietary restrictions.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.