Pregnancy Weight Gain Calculator
Check whether your pregnancy weight gain is on track with IOM guidelines.
Pregnancy Weight Gain Calculator — your inputs
- Pre-pregnancy height
- 165 cm
- Pre-pregnancy weight
- 62 kg
- Current week
- 20 wks
- Current weight
- 67 kg
- Pregnancy type
- Singleton
- Unit system
- Metric
Key takeaways
- Recommended gain depends on your pre-pregnancy BMI, not your current weight — a lower starting BMI means a higher recommended gain.1
- For a normal-BMI single pregnancy the range is 11.5–16 kg (25–35 lb).1
- "Eating for two" is wrong by a factor of about ten. The first trimester needs no extra calories; the second adds ~340/day and the third ~450.5
- Both too little and too much gain carry risk. Goldstein's meta-analysis of over a million pregnancies found 47% gained above the guideline and 23% below.3
- The trajectory matters more than the total — steady gain in the expected pattern is the useful signal.4
How to use this calculator
Enter your pre-pregnancy height and weight, current week, and current weight.
Choose singleton or twins.
Understanding your result
Recommended total gain depends on your pre-pregnancy BMI, with different ranges for singleton and twin pregnancies.
The calculator compares your gain so far against the expected trajectory for your current week and shows on-track / below / above.
Where the ranges come from
The recommendations this calculator applies were set by the Institute of Medicine (now the National Academy of Medicine) in 2009, revising guidance that dated back to 1990, and they were endorsed by ACOG.12 The 2009 revision mattered because it was the first to use the WHO BMI categories and the first to set an upper limit for women with obesity.
The counterintuitive part is that the ranges run inversely to starting BMI: the lower your pre-pregnancy BMI, the more weight you are advised to gain. The reasoning is that a woman starting with fewer energy reserves has less to draw on, and low gestational gain in that group is associated with preterm birth and small-for-gestational-age babies.
| Pre-pregnancy BMI | Total gain (kg) | Total gain (lb) | Weekly, 2nd–3rd trimester |
|---|---|---|---|
| Underweight (< 18.5) (warning) | 12.5 – 18 | 28 – 40 | 0.51 kg |
| Normal (18.5 – 24.9) (success) | 11.5 – 16 | 25 – 35 | 0.42 kg |
| Overweight (25 – 29.9) (warning) | 7 – 11.5 | 15 – 25 | 0.28 kg |
| Obese (≥ 30) (danger) | 5 – 9 | 11 – 20 | 0.22 kg |
Use your pre-pregnancy BMI
BMI computed during pregnancy is not interpretable — weight gain is expected and healthy. Everything on this page is anchored to what you weighed before, which is why that is the input the calculator asks for.
"Eating for two" and what the numbers actually are
This is probably the single most consequential piece of misinformation in pregnancy. A second adult would need roughly 2,000 extra calories a day. A pregnancy needs a small fraction of that.
- First trimester0 extra kcal/day
No increase needed
- Second trimester340 extra kcal/day
About a sandwich
- Third trimester450 extra kcal/day
A sandwich and a yoghurt
- "Eating for two"2000 extra kcal/day
Roughly ten times too much
| Method | Value (extra kcal/day) |
|---|---|
| First trimester | 0 |
| Second trimester | 340 |
| Third trimester | 450 |
| "Eating for two" | 2000 |
340 and 450 calories are small amounts — a sandwich, or a bowl of porridge with fruit and nuts.5 What rises much more sharply than energy needs is the requirement for specific nutrients: folate, iron, iodine, calcium and choline all increase disproportionately, which is why the emphasis in pregnancy nutrition is on food quality rather than quantity.
Do not diet during pregnancy
Deliberate weight loss is not recommended even for women starting with obesity, and no one should be in a calorie deficit while pregnant. If gain is running above the guideline, the approach is to slow the rate through food quality and activity — with your care team — not to restrict.
Why the trajectory matters more than the total
A total is only knowable at the end. What is useful during a pregnancy is whether the pattern looks right, and the expected pattern is not linear.
- First trimester: 0.5–2 kg total. Very little, and losing a little to nausea is common and generally not a concern.
- Second and third trimesters: steady weekly gain at the rate in the table above. This is where nearly all of it happens.
- A sudden jump — more than about 1 kg in a week in the third trimester — is worth mentioning to your midwife or doctor, since rapid gain with swelling can be a sign of pre-eclampsia.
- A plateau or loss in the second half is also worth raising.
Hutcheon and colleagues built gestational weight gain charts by BMI group precisely because a single total obscures this — the same end point can be reached by very different and not equally healthy routes.4
| Component | Approximate weight |
|---|---|
| Baby | 3.4 kg |
| Placenta | 0.7 kg |
| Amniotic fluid | 0.9 kg |
| Uterus | 0.9 kg |
| Breast tissue | 0.9 kg |
| Increased blood volume | 1.8 kg |
| Fluid in tissues | 1.8 kg |
| Maternal fat stores | 2.7 kg |
What happens outside the range
Goldstein and colleagues pooled 23 studies covering more than 1.3 million pregnancies to quantify this, and the headline finding is how normal it is to fall outside the guideline: 47% gained above it and 23% below, leaving only about 30% within.3
| Gain | Associated with |
|---|---|
| Below the range (warning) | Higher risk of preterm birth and small-for-gestational-age infants |
| Above the range (warning) | Higher risk of large-for-gestational-age infants, caesarean delivery and postpartum weight retention |
If you are outside the range
It is common, and it is a conversation with your care team rather than a cause for alarm. They can see the whole picture — your scans, your blood pressure, your history — which is exactly what a calculator cannot.
For the pregnancy timeline itself, the Due Date Calculator gives a dated week-by-week breakdown you can track this against.
Terms used on this page
- Gestational weight gain
- Total weight gained from pre-pregnancy weight to delivery. The measure all the guidelines are written against.
- Pre-pregnancy BMI
- BMI calculated from weight before conception. The single input that determines your recommended range, and the reason a mid-pregnancy BMI is not useful.
- Small / large for gestational age
- Birth weight below the 10th or above the 90th percentile for gestational age. The two outcomes most associated with gain below and above the recommended range.
- Pre-eclampsia
- A pregnancy complication involving high blood pressure and organ stress. Sudden weight gain with swelling can be an early sign, which is why an unexpected jump is worth reporting.
The formula
- Normal BMI, week 20, singleton
- Expected ≈ 5.5 kg by week 20
Source: IOM / NAM pregnancy gain guidelines. Published clinical/scientific formula.
Limitations
- Guidelines are population ranges; individual needs vary — follow your maternity team's advice.
- Pre-pregnancy BMI uses adult WHO bands, which is the IOM convention.
References
- 1.Weight Gain During Pregnancy: Reexamining the Guidelines. Institute of Medicine and National Research Council, National Academies Press, 2009.
- 2.Committee Opinion No. 548: Weight Gain During Pregnancy. American College of Obstetricians and Gynecologists, 2013 (reaffirmed 2020).
- 3.Association of gestational weight gain with maternal and infant outcomes: a systematic review and meta-analysis. Goldstein et al., JAMA 317(21):2207–2225, 2017.
- 4.Gestational weight gain charts for different body mass index groups. Hutcheon et al., American Journal of Clinical Nutrition 111(2):396–405, 2020.
- 5.Nutrition During Pregnancy (Committee Opinion). American College of Obstetricians and Gynecologists, 2023.
Frequently asked questions
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Read articleNot medical advice. This calculator is for general informational purposes only and is not a substitute for professional medical guidance. Always consult a qualified healthcare provider before making decisions about your health. Read the full medical disclaimer.
Printed from mystatura.com — for general information only, not medical advice.