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Pregnancy Weight Gain Calculator

Track recommended weight gain by week per IOM 2009 guidelines based on pre-pregnancy BMI. Singleton + twins. Live curve chart.

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Pregnancy Weight Gain Calculator

Generated on April 25, 2026

On track
+5.0 kg gained
Total target by week 40: 11.5-16 kg(Pre-preg BMI: 22.0 — Normal)

Recommended weight-gain curve

Green band = IOM 2009 recommended range. Pink dot = your current gain at week 20.

Step-by-step calculation

Formula

Pre-pregnancy BMI = weight (kg) / height (m)². IOM 2009 ranges: Underweight 12.5-18 kg, Normal 11.5-16, Overweight 7-11.5, Obese 5-9 (singleton).

  1. 1Pre-pregnancy weight: 60.0 kg, height: 165.0 cm.
  2. 2Pre-pregnancy BMI: 60.0 / 1.65² = 22.04 → Normal (BMI 18.5-24.9).
  3. 3Recommended total gain: 11.5-16 kg over 40 weeks.
  4. 4Current weight: 65.0 kg → gained 5.0 kg by week 20.
  5. 5First trimester typically adds only 0.5-2 kg. Most gain happens in trimesters 2 and 3 (~0.4-0.5 kg/week for normal-BMI women).
Based on IOM (Institute of Medicine, USA) 2009 guidelines. Your obstetrician may recommend different targets based on individual circumstances (gestational diabetes, hyperemesis, etc.). Pakistani / South Asian women often have higher visceral fat at the same BMI — discuss with your doctor whether ethnicity-adjusted ranges apply.

?What is the Pregnancy Weight Gain Calculator?

The Pregnancy Weight Gain Calculator tracks recommended weight gain throughout pregnancy based on pre-pregnancy BMI — per the Institute of Medicine (IOM) 2009 guidelines, which remain the global standard. Underweight women should gain more (12.5-18 kg), normal-BMI women 11.5-16 kg, overweight 7-11.5 kg, and obese 5-9 kg over a singleton 40-week pregnancy. Twins targets are higher (16.8-24.5 kg for normal BMI). The visual curve shows the recommended range week-by-week with your current gain plotted as a marker.

The Formula

Pre-pregnancy BMI determines target gain range. First trimester: ~0.5-2 kg total. Second + third: ~0.4-0.5 kg/week (normal-BMI women).

Total recommended gain per IOM 2009 (singleton): 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. The first trimester adds little weight (mostly increased blood volume, breast tissue, slight uterus growth). Most weight gain happens in trimesters 2 and 3 — at a steady rate. Twin pregnancies target higher: 16.8-24.5 kg for normal BMI.

Practical Examples

1

Pre-pregnancy 60 kg, 165 cm woman (BMI 22, normal): target 11.5-16 kg total gain over 40 weeks.

2

Underweight pre-pregnancy (BMI 17.5): target 12.5-18 kg — more than normal-BMI women, to support fetal growth.

3

Obese pre-pregnancy (BMI 32): target 5-9 kg — lower target reduces gestational diabetes and pre-eclampsia risk.

4

Twins pregnancy (normal pre-BMI): target 16.8-24.5 kg — significantly more than singleton.

5

First trimester: typical gain 0.5-2 kg (often nausea-limited). Don't worry if you lose a little.

Frequently Asked Questions

IOM 2009 is US-based. For Pakistani / South Asian women — who typically have higher visceral fat at the same BMI — some doctors apply slightly lower targets to reduce gestational diabetes risk. Discuss with your obstetrician.

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