How much weight should I gain during pregnancy?

Total recommended weight gain depends on your pre-pregnancy BMI: underweight (BMI =30) 11-20 lb. Twin pregnancies add approximately 10-20 lb to these ranges. This guidance comes from the Institute of Medicine (IOM) 2009 report.

How is pregnancy weight gain distributed by trimester?

In the first trimester (weeks 1-13), total gain is small — typically 1-5 lb regardless of BMI. Most weight gain occurs in the second and third trimesters at a steady weekly pace: about 1 lb/week for underweight, 0.8 lb/week for normal BMI, 0.6 lb/week for overweight, and 0.5 lb/week for obese women.

How much should I gain with twins?

For twin pregnancies, IOM provisional guidelines recommend: normal BMI 37-54 lb, overweight 31-50 lb, obese 25-42 lb. There is no formal recommendation for underweight women with twins, but a gain similar to or higher than the normal BMI range is typical. Twin pregnancies require more calories and nutrients than singleton pregnancies.

What if I'm overweight or obese before pregnancy?

Overweight women (BMI 25-29.9) should aim for 15-25 lb total gain, and obese women (BMI >=30) should aim for 11-20 lb for a singleton pregnancy. Gaining at the lower end of the range — or even slightly below in some cases of obesity — is associated with better outcomes. Never attempt active weight loss during pregnancy without medical supervision.

Is it bad to gain too fast in pregnancy?

Gaining significantly above the recommended range increases the risk of gestational diabetes, preeclampsia, cesarean delivery, and postpartum weight retention. A sudden jump of more than 2 lb in a single week — especially combined with swelling, headaches, or vision changes — can signal preeclampsia and needs immediate medical attention.

Is low weight gain during pregnancy dangerous?

Gaining too little increases the risk of preterm birth and low-birth-weight babies. This is especially concerning for underweight women. First-trimester weight loss of a few pounds from nausea is usually fine, but persistent weight loss or failure to gain in the 2nd/3rd trimester needs evaluation by your obstetric provider.

How does this calculator work?

Enter your pre-pregnancy weight and height to compute pre-pregnancy BMI, select singleton or twin pregnancy, then enter your current week and current weight. The calculator applies IOM 2009 guidelines to your BMI category, projects the recommended total and at-week cumulative gain, and tells you whether your current gain is below, on-track, or above the healthy range.

Does the calculator replace prenatal care?

No. This calculator provides general IOM-based guidance for healthy pregnancy weight tracking but does not replace individualized prenatal care. Your provider considers other factors — fetal growth, blood pressure, gestational diabetes risk, fluid balance — that this tool cannot evaluate. Always share any concerns about weight gain with your obstetric provider.

Pregnancy Weight Gain Calculator

Healthy pregnancy weight gain depends on pre-pregnancy BMI, not a single one-size-fits-all target. Underweight women should gain more (28-40 lb), normal-weight women 25-35 lb, overweight women 15-25 lb, and women with obesity 11-20 lb for a singleton pregnancy. Our calculator applies the IOM 2009 guidelines, tells you where you should be at your current week, compares your actual gain to the range, and shows the recommended pace (lb/week) for the remaining weeks. Twin pregnancies require roughly 10-20 lb more gain than singletons. Use this tool alongside prenatal care — it complements but does not replace your provider.

star 4.8 (348 ratings)

calendar_today Updated: April 2026

auto_awesome AI Insights AI

New

pregnant_woman Your Pregnancy Info

Unit System

Pre-pregnancy Weight (lb)

Height (in)

Current Week

Current Weight (lb)

Pregnancy Type

monitoring Your Gain Status

Pre-pregnancy BMI

23.3

Normal

Current Gain

12.0 lb

On track

Recommended Total Gain

25.0-35.0 lb

Recommended at Week 20

7.6-10.6 lb

Weekly Pace Going Forward

0.65-1.10 lb/week for 20 weeks remaining

Guidance

Your current weight gain aligns with IOM recommendations for your BMI, pregnancy type, and week. Keep it steady.

Input Values

Unit

Imperial (lb, in)

Metric (kg, cm)

Pre-pregnancy Weight

Height

Current Week

Current Weight

Pregnancy Type

Singleton

Twins

tips_and_updates Tips

• Pregnancy weight gain targets depend on pre-pregnancy BMI, not current weight
• First-trimester gain is small (1-5 lb) for all BMI categories — don't worry if you gain little or even lose weight due to nausea
• Most weight gain happens in the 2nd and 3rd trimesters — aim for about 0.5-1 lb/week depending on your BMI
• Twin pregnancies add ~10-20 lb to the total range (Normal BMI twins: 37-54 lb)
• Underweight before pregnancy? Gain on the higher end (28-40 lb) for singleton
• Obese before pregnancy? Lower-end gain (11-20 lb) is safer for mom and baby
• Sudden gain >2 lb in one week can signal preeclampsia — contact your provider
• Healthy gain is gradual: steady small increases, not swings

How to Use This Calculator

Choose units

Pick imperial (lb/in) or metric (kg/cm). All inputs will use the selected system.

Enter pre-pregnancy weight and height

These determine your pre-pregnancy BMI, which sets your recommended gain range.

Select pregnancy type

Singleton or twins — twin pregnancies require more weight gain.

Enter current week and weight

The calculator compares your current gain to the recommended cumulative gain for that week.

Review status and pace

See if you are below, on-track, or above, and the recommended weekly pace for the remaining weeks.

The Formula

Pre-pregnancy BMI determines your total recommended weight gain range. Gain 1-5 lb in the first trimester, then add the appropriate weekly pace each week after: ~1 lb/week (underweight), 0.8 lb/week (normal), 0.6 lb/week (overweight), 0.5 lb/week (obese). Twin pregnancies shift the total range up by ~10-20 lb.

Pre-pregnancy BMI -> IOM total gain range -> weekly pace after 1st trimester

lightbulb Variables Explained

BMI Pre-pregnancy BMI = weight(kg) / height(m)^2
T1 gain Total gain in weeks 1-13 (typically 1-5 lb)
T2/T3 pace Weekly gain after week 13, based on BMI category

tips_and_updates Pro Tips

Pregnancy weight gain targets depend on pre-pregnancy BMI, not current weight

First-trimester gain is small (1-5 lb) for all BMI categories — don't worry if you gain little or even lose weight due to nausea

Most weight gain happens in the 2nd and 3rd trimesters — aim for about 0.5-1 lb/week depending on your BMI

Twin pregnancies add ~10-20 lb to the total range (Normal BMI twins: 37-54 lb)

Underweight before pregnancy? Gain on the higher end (28-40 lb) for singleton

Obese before pregnancy? Lower-end gain (11-20 lb) is safer for mom and baby

Sudden gain >2 lb in one week can signal preeclampsia — contact your provider

Healthy gain is gradual: steady small increases, not swings

The Institute of Medicine's 2009 report on pregnancy weight gain tied the target range directly to pre-pregnancy BMI rather than a universal number. Underweight women (BMI <18.5) are asked to gain more — 28-40 lb for a singleton — because lower gain is linked to preterm birth and small-for-gestational-age babies. Normal BMI women aim for 25-35 lb. Overweight and obese women have lower ranges (15-25 lb and 11-20 lb, respectively) since excessive gain in those groups is tied to gestational diabetes, preeclampsia, and cesarean risk. Twin pregnancies add about 10-20 lb because two fetuses, two placentas, and extra amniotic fluid require more maternal tissue growth.

Weight gain in pregnancy is not linear — nor is it meant to be. The first trimester typically adds only 1-5 lb total, often less if morning sickness limits appetite. The second and third trimesters do most of the work, with fairly steady weekly gain: about 0.8 lb/week for normal-BMI women, higher for underweight, lower for overweight or obese. Our calculator projects where your cumulative gain should be at any given week, compares your actual weight, and suggests the weekly pace for the weeks ahead so you stay within IOM-recommended territory.

Frequently Asked Questions

Related Tools

View all Health & Fitness View all arrow_forward

health_and_safety