Pregnancy Weight Gain Calculator
Track pregnancy weight gain against IOM guidelines for your pre-pregnancy BMI.
Inputs
Weight gained so far
7.0kg
Pre-pregnancy BMI
23.9
BMI category
Normal weight
IOM recommended min (total)
11.5kg
IOM recommended max (total)
16.0kg
Expected gain by now (min)
3.4kg
Expected gain by now (max)
5.6kg
Status vs. IOM guideline
Above recommended range
Remaining gain needed (min)
4.5kg
Remaining gain allowed (max)
9.0kg
Step by step
Pre-pregnancy BMI
65 / 1.65²
= 23.9
BMI category
= Normal weight
IOM total gain range
= 11.5 – 16 kg
Weight gained so far
= 7.0 kg
Expected range at week 20
= 3.4 – 5.6 kg
Status
= Above recommended range
How it works
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.
Formula
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.
Frequently Asked Questions
What are the IOM 2009 recommended ranges?
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.
Is the weekly rate of gain consistent throughout pregnancy?
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.
Should I be concerned if I'm outside the range?
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.