Pregnancy Weight Gain Calculator
Estimate a general weight gain range from your pre-pregnancy BMI and current week of pregnancy. The result is guidance, not a personal clinical target.
Enter your details above to see your result
⚠️ This tool provides general guideline ranges only. It does not replace medical advice. Always consult your doctor or midwife for personalised guidance.
Recommended Weight Gain by BMI
These are general pregnancy weight-gain ranges grouped by pre-pregnancy BMI. Your GP or midwife may recommend a different target for your individual situation.
| Pre-pregnancy BMI | Category | Recommended Gain |
|---|---|---|
| Below 18.5 | Underweight | 12.5 – 18 kg |
| 18.5 – 24.9 | Healthy | 11.5 – 16 kg |
| 25.0 – 29.9 | Overweight | 7 – 11.5 kg |
| 30.0 or above | Obese | 5 – 9 kg |
How Weight Gain Works During Pregnancy
Pregnancy weight gain is not just about the baby. It includes the placenta, amniotic fluid, increased blood volume, breast tissue growth, uterus enlargement, and some additional fat stores that help support breastfeeding after birth.
Weight gain tends to follow a pattern. In the first trimester (weeks 1–12), most women gain only 1–3 kg. From the second trimester onwards, a steady gain of around 0.3–0.5 kg per week is typical. The rate slows slightly in the final weeks as the body prepares for delivery.
Baby
3–4 kg
Placenta + Fluid
2–3 kg
Blood + Uterus
3–4 kg
Fat Stores
2–4 kg
Medical Disclaimer
This calculator provides general guideline ranges based on pre-pregnancy BMI. It does not account for individual medical conditions, multiple pregnancies (twins), or other complicating factors. Always consult your GP, midwife, or obstetrician for personalised weight gain advice during pregnancy.
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Frequently Asked Questions
How much weight should I gain during pregnancy?
Recommended weight gain depends on your pre-pregnancy BMI. For a healthy BMI (18.5–24.9), the general guideline is 11.5–16 kg. Underweight women may be advised to gain 12.5–18 kg, while overweight women typically aim for 7–11.5 kg. These are general ranges: your doctor or midwife will give you a personalised target.
Is gaining less weight than recommended a concern?
Gaining less than the recommended range can sometimes be associated with lower birth weight. However, many factors influence pregnancy outcomes. If you are concerned about your weight gain, speak to your midwife or GP who can assess your individual situation.
Does my BMI affect how much weight I should gain?
Yes. Pre-pregnancy BMI is the primary factor that determines your recommended weight gain range. Women who start pregnancy at a higher BMI are generally advised to gain less, while those with a lower BMI may be encouraged to gain more.
When does most pregnancy weight gain happen?
Weight gain is typically minimal in the first trimester (1–3 kg). The majority of weight gain happens in the second and third trimesters, when the baby, placenta, and amniotic fluid are growing rapidly. A steady gain of around 0.4–0.5 kg per week is common in the second half of pregnancy.
What does pregnancy weight gain consist of?
Only a portion is the baby itself (typically 3–4 kg at birth). The rest includes the placenta, amniotic fluid, increased blood volume, breast tissue growth, uterus enlargement, and some additional fat stores that support breastfeeding. This is why the recommended total is higher than just the baby's weight.