Healthy weight gain in pregnancy depends on your pre-pregnancy BMI. This calculator uses the Institute of Medicine (IOM) 2009 guidelines - the standard recommendation in India and globally - to give a recommended total range and weekly target.
Pre-pregnancy BMI
22.0
Normal
Recommended total gain
11.5–16 kg
IOM 2009 guidelines
Avg weekly (after wk 13)
0.46 kg
On track
By week 20, you'd typically have gained around 4.6 kg. You've gained 4.0 kg.
IOM 2009 recommendations
Underweight: 12.5-18 kg · Normal: 11.5-16 kg · Overweight: 7-11.5 kg · Obese: 5-9 kg
First trimester gain is small (~0.5-2 kg). Most weight goes on after week 13.
For singleton pregnancy. Twin and multiple pregnancies need more. Always discuss your weight gain with your obstetrician - individual circumstances (diabetes, hypertension, hyperemesis) change recommendations.
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Pregnancy weight gain is a critical health marker for both mother and baby. Insufficient gain (under 7 kg in a normal-BMI singleton pregnancy) raises risks of preterm birth, low birth weight, and developmental issues. Excessive gain (over 18-20 kg) raises risks of gestational diabetes, hypertension, large-for-gestational-age babies requiring C-section, and post-pregnancy weight retention. The Institute of Medicine's 2009 guidelines, used globally and in Indian obstetric care, give specific gain ranges tied to your pre-pregnancy BMI.
This calculator computes your pre-pregnancy BMI category and the recommended total weight gain range, then tracks your progress against your current week of pregnancy. Use it weekly or biweekly to ensure you're tracking within the healthy range. Most weight gain happens in trimesters 2 and 3 - the first trimester typically adds 0.5-2 kg total, with the bulk of gain coming in the back half of pregnancy at roughly 0.4-0.5 kg per week for normal-BMI women.
Enter your pre-pregnancy weight and height.
We compute your pre-pregnancy BMI and the IOM-recommended total gain.
Enter your current week of pregnancy and current weight to track progress.
Compare your current gain to the recommended range.
IOM 2009 ties total weight gain to pre-pregnancy BMI. Underweight women need to gain more (12.5-18 kg); obese women less (5-9 kg). Most gain happens after week 13, averaging 0.4-0.5 kg per week for women with normal pre-pregnancy BMI.
Underweight (<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
IOM 2009 weight gain ranges by pre-pregnancy BMI category: Underweight (BMI <18.5): 12.5-18 kg total. Normal (BMI 18.5-24.9): 11.5-16 kg total. Overweight (BMI 25-29.9): 7-11.5 kg total. Obese (BMI ≥30): 5-9 kg total. These ranges are for singleton pregnancies. Twin pregnancies need substantially more: typically 17-25 kg for normal-BMI women.
Weight gain distribution by trimester: Trimester 1 (weeks 1-13): 0.5-2 kg total - minimal change, sometimes loss from morning sickness. Trimester 2 (weeks 14-27): 5-6 kg, averaging 0.4-0.5 kg/week for normal-BMI. Trimester 3 (weeks 28-40): 5-6 kg, averaging 0.4-0.5 kg/week. The steady weekly gain rate in trimesters 2-3 is the key marker - sudden jumps or stalls warrant medical attention.
Where the weight goes (typical for a 12 kg gain): Baby: 3-4 kg. Placenta: 0.7 kg. Amniotic fluid: 0.9 kg. Uterus enlargement: 1 kg. Breast tissue increase: 0.5-1.5 kg. Increased blood and fluid volume: 2-3 kg. Maternal fat stores (for breastfeeding): 2-4 kg. Understanding the breakdown helps explain why even women who 'don't look very pregnant' can gain 10+ kg by term.
Normal BMI. IOM target: 11.5-16 kg total over 40 weeks. By week 24, expected gain is roughly 5-7 kg (passed first trimester slow gain + 11 weeks at 0.4-0.5 kg/week). Current gain 7 kg - tracking at the upper edge of normal. Continue at 0.4 kg/week pace through trimester 3.
Overweight BMI. IOM target: 7-11.5 kg total. By week 30, expected gain is ~5-8 kg. Current gain 9 kg - at the upper end of overweight range. May need to slow gain in trimester 3 to stay within IOM target - discuss with obstetrician about diet adjustments without restriction.
Yes. Twin pregnancies need higher gain - typically 17-25 kg for normal-BMI women. Speak to your obstetrician for multiples.
Baby (3-4 kg), placenta (0.7 kg), amniotic fluid (0.9 kg), uterus growth (1 kg), increased blood volume (1.5 kg), breast tissue (0.5-1.5 kg), fat stores (2-4 kg). The rest is fluid retention.
Don't crash diet - focus on portion control, more vegetables, less ultra-processed food. Speak to your obstetrician before any deliberate restriction. Excess weight gain raises gestational diabetes risk.
Severe under-gain raises preterm birth and low-birthweight risk. Add nutrient-dense calories - nuts, dairy, eggs, ghee, fruits. Consult your doctor if gain stalls for 2+ weeks.
Mild loss in the first trimester from morning sickness is common and not concerning. Persistent loss past week 12 needs medical attention.
Yes - IOM is the global standard and Indian obstetricians use it. Some doctors apply the Asian-BMI cutoffs (lower thresholds for overweight/obese), in which case use the Asian-BMI category.
Body composition, daily energy needs and pregnancy timelines all rest on formulas validated across millions of people, but no single number tells the whole story. The values from this calculator are point estimates with a known margin of error - body fat from skinfold or US Navy method has roughly a ±3% standard error compared to a DEXA scan, and BMR can vary ±10% person to person at the same height and weight. Use these numbers to track trends week over week, not to chase decimal precision day to day.
Pair this tool with the BMR, TDEE, calorie and macro calculators to turn a single measurement into an actionable plan. None of these tools are a substitute for a qualified doctor, registered dietitian or certified strength coach - but they remove the busywork so you spend more time on training and recovery, less on math.
The Pregnancy Weight Gain Calculator is part of the Health & Fitness suite on Online Calculator Tools, alongside 6 related calculators. All tools share the same UI patterns, the same privacy-first rendering (nothing is sent to a server), and the same commitment to showing the formula and assumptions behind every result.
