Pregnancy Weight Gain Calculator
Understand your healthy weight gain targets. Enter your pre-pregnancy details to get personalised, trimester-by-trimester recommendations based on medical guidelines.
Calculate Your Healthy Targets
Use our evidence-based calculator to determine your recommended weight gain range, aligned with the Institute of Medicine (IOM) and UK NHS guidelines.
Weight Gain Estimator
Enter your pre-pregnancy details for an instant breakdown.
Where Does the Weight Go?
Breakdown of a typical 12-14 kg gain
Managing Weight During Pregnancy
Healthy weight gain is about nourishing your baby and your body, not “eating for two” in terms of calories. Focus on quality and steady progress.
First Trimester: Minimal Gain
Most women only need to gain 1 to 2 kg total during the first 12 weeks. Morning sickness may even cause slight weight loss, which is usually fine if you can stay hydrated. No extra calories are needed yet.
Second & Third Trimester: Steady Gain
This is when the baby grows most rapidly. You only need about 200–300 extra calories per day (equivalent to a slice of toast with peanut butter and a glass of milk). Focus on nutrient-dense foods.
Prioritise Nutrient Density
Choose foods rich in folate, iron, calcium, and protein. Lean meats, leafy greens, dairy, whole grains, and healthy fats support fetal development without excessive empty calories.
Stay Active (If Cleared)
Unless advised otherwise by your doctor, 150 minutes of moderate-intensity exercise per week (like brisk walking, swimming, or prenatal yoga) helps manage weight, improves mood, and prepares your body for labour.
Red Flags to Discuss
When to contact your healthcare provider
IOM Weight Gain Guidelines
The standard medical recommendations for total weight gain and rate of gain during pregnancy, based on pre-pregnancy Body Mass Index (BMI).
| Pre-pregnancy BMI | BMI Category | Recommended Total Gain (Singleton) | Recommended Weekly Gain (2nd/3rd Tri) |
|---|---|---|---|
| Less than 18.5 | Underweight | 12.5 – 18 kg (28 – 40 lbs) | 0.44 – 0.58 kg / week |
| 18.5 – 24.9 | Normal weight | 11.5 – 16 kg (25 – 35 lbs) | 0.35 – 0.50 kg / week |
| 25.0 – 29.9 | Overweight | 7.0 – 11.5 kg (15 – 25 lbs) | 0.23 – 0.33 kg / week |
| 30.0 and above | Obese | 5.0 – 9.0 kg (11 – 20 lbs) | 0.17 – 0.27 kg / week |
* For twin pregnancies, recommended total gain is typically 17–25 kg (normal BMI), 14–23 kg (overweight), or 11–19 kg (obese). Always consult your obstetrician for multiple pregnancy targets.
Pregnancy Weight FAQ
Answers to the most frequently asked questions about weight management and health during pregnancy.
It depends on your pre-pregnancy BMI. For a normal BMI (18.5–24.9), the recommended total weight gain is 11.5 to 16 kg (25–35 lbs). Underweight individuals should gain 12.5–18 kg, overweight 7–11.5 kg, and obese 5–9 kg.
Yes. For a twin pregnancy, the recommended weight gain is higher. For a normal pre-pregnancy BMI, the target is 17 to 25 kg (37–54 lbs). Overweight individuals should aim for 14–23 kg, and obese individuals for 11–19 kg.
The weight is distributed across the baby (approx. 3-3.5 kg), placenta, amniotic fluid, increased blood volume, breast tissue, uterine growth, and essential maternal fat stores for breastfeeding and energy.
Gaining outside the recommended ranges can increase risks such as gestational diabetes, high blood pressure, preterm birth, or low birth weight. Always discuss your weight trajectory with your midwife or GP, who can provide personalised advice.