Health & Fitness · Pregnancy
Pregnancy Weight Gain Calculator — Healthy Range by Week
Find the healthy amount of weight to gain during pregnancy from your pre-pregnancy weight and height, using the US Institute of Medicine (2009) guidelines: the total for the whole pregnancy, the recommended range at your current week, the weekly rate for the second and third trimesters, and — if you enter your weight today — whether you're below, within or above the range. Includes the provisional ranges for twins.
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Recommended Total Gain
11.5 kg – 16.0 kg
Pre-pregnancy BMI 22.7 — normal weight
- Range at Week 20
- 2.9 kg – 5.5 kg gained so far (weight 61.0 kg – 63.5 kg)
- Weekly Rate, Weeks 14–40
- 0.35 kg – 0.50 kg a week
- First Trimester
- 0.5 kg – 2.0 kg in total over weeks 1–13
Recommended gain by week
9 rowsThese are US Institute of Medicine (2009) ranges using standard WHO BMI categories. Your doctor or midwife may set a different target — for example using lower Asian BMI cut-offs — and will track your weight at check-ups.
Don't diet to lose weight in pregnancy unless your doctor advises it.
Population-average estimates for healthy adults, not medical advice. Talk to a doctor or registered dietitian before major changes to diet or exercise, or if you are pregnant or have a health condition.
How this is calculated
BMI = weight before pregnancy ÷ height² · weeks 1–13: 0.5–2 kg in total · then + weekly rate × (week − 13)
- Weekly rate
- Underweight 0.44–0.58, normal 0.35–0.50, overweight 0.23–0.33, obese 0.17–0.27 kg a week
How much to gain depends on your weight before pregnancy. Women who started underweight should gain more (12.5–18 kg), those of normal weight 11.5–16 kg, overweight 7–11.5 kg, and obese 5–9 kg. Most of the gain comes after the first trimester, at a fairly steady weekly rate. Twin pregnancies need more.
Assumptions & sources
- IOM 2009 guidelines; first-trimester gain of 0.5–2 kg, then a steady weekly rate.
- 1Weight Gain During Pregnancy: Reexamining the Guidelines — Institute of Medicine and National Research Council, 2009
- 2Gestational weight gain recommendations by pre-pregnancy BMI (IOM 2009; ACOG Committee Opinion 548) — Diabetologia (PMC6434527)
Calculator ID HLTH-PREG-WEIGHT-001 · version 1.0.0
Common questions
How much weight should I gain if my BMI is normal?
11.5–16 kg (25–35 lb) over the whole pregnancy, about 0.35–0.5 kg a week after the first trimester.
How much weight do you gain in the first trimester?
Usually only 0.5–2 kg (1–4.5 lb); most of the gain comes later.
How much should I gain with twins?
IOM provisional ranges: 17–25 kg for normal weight, 14–23 kg overweight and 11–19 kg obese.