Pregnancy Weight Gain Calculator by BMI & Week

Calculate your ideal pregnancy weight gain by week based on your BMI using official IOM guidelines. Get personalized targets for singleton or twin pregnancies with calorie recommendations. Trusted by moms & doctors.

Pregnancy Weight Gain Calculator (Advanced)

Units

Metric (kg, cm) Imperial (lb, ft+in)

Pregnancy Type

Singleton Twins

Pre-pregnancy Weight (kg)

Height (cm)

Current Week of Pregnancy (1–42)

Current Weight (optional) (kg)

Age (optional; for calorie estimate)

Activity Level (for calorie estimate)

No data is stored; all calculations run in your browser.

About Pregnancy Weight Gain

Healthy weight gain during pregnancy is important for both mother and baby. The amount of weight you should gain depends on your pre-pregnancy Body Mass Index (BMI).

Recommended Weight Gain

Pre-pregnancy BMI	BMI Range	Singleton Pregnancy	Twin Pregnancy
Underweight	< 18.5	12.5–18 kg (28–40 lbs)	17–25 kg (37–55 lbs)
Normal weight	18.5–24.9	11.5–16 kg (25–35 lbs)	17–25 kg (37–55 lbs)
Overweight	25–29.9	7–11.5 kg (15–25 lbs)	14–23 kg (31–50 lbs)
Obese	≥ 30	5–9 kg (11–20 lbs)	11–19 kg (25–42 lbs)

Weight Gain Patterns

Weight gain during pregnancy typically follows this pattern:

First trimester (weeks 1–13): 0.5–2 kg (1–4.5 lbs) total
Second trimester (weeks 14–27): ~0.35–0.5 kg (0.8–1 lb) per week
Third trimester (weeks 28–40): Continued steady gain until delivery

Nutritional Needs

Caloric needs increase during pregnancy:

First trimester: No extra calories needed for most women
Second trimester: About 340 extra calories per day
Third trimester: About 450 extra calories per day

References:
1. Institute of Medicine (US) & National Research Council (US). (2009). Weight Gain During Pregnancy: Reexamining the Guidelines. National Academies Press.
2. American College of Obstetricians and Gynecologists. (2013). Weight Gain During Pregnancy.
3. Luke B, et al. (2005). Gestational weight gain and twin pregnancy outcome. Obstet Gynecol.

Track Your Healthy Pregnancy Weight Gain

Our advanced pregnancy weight calculator helps you:

Get personalized weekly weight gain targets based on your pre-pregnancy BMI
See if you’re on track with visual charts & progress indicators
Understand IOM recommendations for singleton & twin pregnancies
Calculate additional calorie needs by trimester
Download PDF reports to share with your doctor

How Much Weight Should You Gain During Pregnancy?

Every pregnancy is unique, but medical guidelines from the Institute of Medicine (IOM) provide healthy weight gain ranges based on your pre-pregnancy Body Mass Index (BMI). Our calculator uses these evidence-based standards to give you:
- Week-by-week targets from conception to delivery
- Customized recommendations whether you’re underweight, normal weight, overweight, or obese
- Special calculations for twin pregnancies
- Visual progress tracking with interactive charts
“Proper weight gain during pregnancy reduces risks of complications and supports baby’s healthy development” – American College of Obstetricians and Gynecologists

How to Use This Pregnancy Weight Calculator

Enter your pre-pregnancy weight and height
Select your current pregnancy week (1-42)
Choose singleton or twins pregnancy
Add your current weight (optional) to check your progress
Get instant results with personalized recommendations

Bonus: Download your results as a PDF to discuss with your OB-GYN at your next appointment.

Why Tracking Pregnancy Weight Matters

Maintaining healthy weight gain during pregnancy helps:

Reduce risk of gestational diabetes
Lower chances of high blood pressure disorders
Prevent birth complications
Support baby’s optimal growth
Make postpartum weight loss easier

Our tool follows 2024 medical guidelines to give you the most accurate recommendations.

Pregnancy Weight Gain Guidelines by BMI

Below are the official IOM recommendations our calculator uses:

Pre-Pregnancy BMI	BMI Range	Singleton Pregnancy	Twin Pregnancy
Underweight	<18.5	12.5–18 kg (28–40 lbs)	17–25 kg (37–55 lbs)
Normal weight	18.5–24.9	11.5–16 kg (25–35 lbs)	17–25 kg (37–55 lbs)
Overweight	25–29.9	7–11.5 kg (15–25 lbs)	14–23 kg (31–50 lbs)
Obese	≥30	5–9 kg (11–20 lbs)	11–19 kg (25–42 lbs)

Frequently Asked Questions (FAQs)

How accurate is this pregnancy weight calculator?

Our tool uses official IOM guidelines adopted by obstetricians worldwide. However, individual needs may vary - always consult your doctor.

When should I start tracking pregnancy weight gain?

Ideally from your first prenatal visit, but it's never too late to start. Most weight gain occurs in the 2nd and 3rd trimesters.

What if I'm gaining weight too fast or too slow?

Don't panic! Download your results and discuss them with your healthcare provider, who can assess your individual situation.

How does twin pregnancy weight gain differ?

Twin pregnancies typically require more total weight gain (about 50% more than singletons) with different distribution patterns.

Medical Disclaimer

This calculator provides general information based on standard guidelines. It is not a substitute for professional medical advice. Individual needs may vary based on health conditions, multiple pregnancies, or other factors. Always consult with your healthcare provider about appropriate weight gain during pregnancy.