Enter your weight and height to see your BMI, your category and the total weight gain recommended in pregnancy.
BMI is weight in kilograms divided by the square of height in metres: BMI = weight (kg) / height² (m²). For example, an adult weighing 70 kg who is 1.75 m tall has a BMI of 70 / (1.75 × 1.75) = 22.9 (WHO, 2000).
If you are planning a pregnancy or are pregnant, use your pre-pregnancy weight: recommended weight gain in pregnancy is based on pre-pregnancy BMI (IOM, 2009).
| Category | BMI (kg/m²) | Risk of related conditions |
|---|---|---|
| Underweight | Below 18.50 | Low (but risk of other clinical problems increased) |
| Normal range | 18.50–24.99 | Average |
| Overweight (pre-obese) | 25.00–29.99 | Increased |
| Obese class I | 30.00–34.99 | Moderate |
| Obese class II | 35.00–39.99 | Severe |
| Obese class III | 40.00 or more | Very severe |
These cut-offs are for adults; they do not depend on age and are the same for both sexes (WHO, 2000). The calculator rounds BMI to one decimal place, sets the category from that displayed value and shows four groups (underweight, normal, overweight, obese); you can read your obesity class from this table.
| Pre-pregnancy BMI | Recommended total gain |
|---|---|
| Below 18.5 | 12.5–18 kg |
| 18.5–24.9 | 11.5–16 kg |
| 25.0–29.9 | 7–11.5 kg |
| 30.0 or more | 5–9 kg |
These values are the same in the IOM recommendations and the Turkish Ministry of Health antenatal care guideline (IOM, 2009; Turkish Ministry of Health, 2026). For weekly and monthly advice, see the pregnancy weight gain calculator.
The calculator gives a screening measure; it does not make a diagnosis.
For adults the normal range is 18.50–24.99 (WHO, 2000). The same 18.5–25 range is advised for people planning a pregnancy.
Weight gained in pregnancy raises BMI, and that value is not used to set weight gain goals. The goal is based on BMI calculated from your pre-pregnancy weight or your weight at the first visit (IOM, 2009).
The recommended total gain is 5–9 kg. The Turkish Ministry of Health guideline advises referral to a dietitian, and NICE offers gestational diabetes testing. The safety of intentional weight loss in pregnancy has not been established.
Yes. BMI does not distinguish muscle from fat, so in very muscular people it can overstate body fat. Waist circumference adds information (WHO, 2000).
The WHO classification does not depend on age or sex, but what a given BMI means for risk can differ between populations. The Turkish Ministry of Health guideline uses a BMI cut-off of 23 for people of Asian origin in early gestational diabetes screening.
A BMI below 17 is often linked to missed periods and ovulation problems caused by excessive exercise or too little food (UpToDate, 2026). Reaching a BMI of 18.5–25 before pregnancy is advised; the recommended total gain in pregnancy for underweight women is 12.5–18 kg.
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