A gentle range, not a rule
Pregnancy weight gain calculator
Based on IOM/NAM guidelines: your target depends on your pre-pregnancy BMI, not on one ideal number.
Your details
Week 20
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Your BMI-based target range and progress will appear here after you calculate.
Based on ACOG & NHS guidelines
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Reviewed against the official NHS calculator
How we calculate your target range
We classify your pre-pregnancy BMI using WHO categories, then apply the Institute of Medicine (IOM/NAM) recommended total gain for that category: 12.5–18 kg if underweight, 11.5–16 kg at a healthy weight, 7–11.5 kg if overweight, 5–9 kg with obesity. The weekly target assumes roughly 0.5–2 kg in the first trimester, then a steady weekly gain to week 40. Individual needs vary — your care team knows your history.
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