Pregnancy Weight Gain Calculator (IOM Recommendations)

What this tool does

The US Institute of Medicine (now the National Academy of Medicine) set the best-known guidelines in 2009, and they depend on weight before pregnancy: a total of 12.5–18 kg for underweight, 11.5–16 kg for normal weight, 7–11.5 kg for overweight and 5–9 kg for obesity. Most of it comes later: only 0.5–2 kg is advised in the first 13 weeks, then a steady weekly rate that is higher at a lower starting weight. The figures are for one baby; twins have separate ranges. Weight gain is only one signal, and your midwife or doctor will judge it alongside your own circumstances.

Formula

total gain by pre-pregnancy BMI (IOM 2009): <18.5: 12.5–18 kg · 18.5–24.9: 11.5–16 kg · 25–29.9: 7–11.5 kg · ≥30: 5–9 kg · 0.5–2 kg in the first 13 weeks, then 0.44–0.58 / 0.35–0.50 / 0.23–0.33 / 0.17–0.27 kg per week

Variables

Worked example

Limitations

• This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
• The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.