Track pregnancy weight gain against IOM guidelines for your pre-pregnancy BMI.
The Institute of Medicine (IOM) 2009 guidelines recommend different total weight gain ranges during pregnancy depending on pre-pregnancy BMI. The ranges account for the baby's weight, placenta, amniotic fluid, increased blood volume and breast tissue. Gaining within the recommended range is associated with better outcomes for both mother and baby.
Pre-pregnancy BMI
BMI = weight (kg) / height (m)²
The weight gain ranges in this calculator are based on the 2009 IOM guidelines. They are population-level estimates for informational purposes only. Every pregnancy is different. Consult your healthcare provider for personalised guidance on gestational weight gain.
Underweight (BMI < 18.5): 12.5–18 kg. Normal (18.5–24.9): 11.5–16 kg. Overweight (25–29.9): 7–11.5 kg. Obese (≥ 30): 5–9 kg. For twins with normal BMI the range is 17–25 kg.
No. In the first trimester the typical total gain is only 0.5–2 kg. Thereafter weight gain accelerates, with roughly 0.3–0.5 kg per week in the second and third trimesters. This calculator prorates the total range linearly, which is a simplification.
Not necessarily — individual variation is normal, and weight gain can fluctuate week to week. Discuss any concerns with your midwife or obstetrician rather than attempting to restrict or force weight gain without medical supervision.