Use this pregnancy weight gain calculator to find a personalized weight range based on your pre-pregnancy BMI, current week, and whether you're carrying twins or multiples. Enter your height, pre-pregnancy weight, and due date above to see your recommended weight gain by week and trimester.

Every pregnancy is different. The ranges here follow guidelines from the Institute of Medicine (IOM) and respected health organizations like the American College of Obstetricians and Gynecologists. They give you a ballpark, not a prescription.

How Much Weight Should You Gain During Pregnancy

How much weight you should gain during pregnancy depends mostly on your pre-pregnancy body mass index. It is not a fixed number of pounds or a fixed percentage of your pre-pregnancy weight.

For a single pregnancy, the general targets are:

Underweight (BMI below 18.5): 28 to 40 pounds
Normal weight (BMI 18.5 to 24.9): 25 and 35 pounds
Overweight (BMI 25.0 to 29.9): 15 to 25 pounds
Obese (BMI 30.0 or higher): 11 to 20 pounds

If you're carrying twins or multiples, the recommended weight gain is higher. Women carrying twins at a normal weight typically aim for 37 to 54 pounds. Your health care provider can fine-tune these numbers based on your situation.

Gaining within the recommended range supports a healthy pregnancy, lowers the risk of complications, and helps your baby reach a healthy birth weight. These targets are not about appearance. They exist to support the growth and development of your baby.

Calculate Your Pre-Pregnancy BMI

Your pre-pregnancy BMI is the starting point for every recommendation on this page. BMI stands for body mass index. It is a simple ratio of your weight to your height.

The formula: BMI = weight (kg) ÷ height (m²)

You do not need to do the math yourself. Enter your height and pre-pregnancy weight in the calculator above and it handles the conversion for you.

Body Mass Index and Pre-Pregnancy BMI Categories

BMI groups people into broad categories that help set weight gain goals during pregnancy.

BMI Range	Category
Below 18.5	Underweight
18.5 to 24.9	Normal weight
25.0 to 29.9	Overweight
30.0 and above	Obese

BMI is a screening tool, not a full picture of your health. It does not account for muscle mass, bone density, or body composition. Still, the Institute of Medicine uses these categories because they correlate well with pregnancy outcomes across large populations.

If your BMI chart says you are obese and you're planning a pregnancy, talk to your health care provider about a realistic plan. Even modest weight loss before conception can improve outcomes. But once you are pregnant, the focus shifts to healthy weight gain, not weight loss.

Recommended Weight Gain Goals by Trimester

Pregnancy weight gain does not happen evenly across all nine months. Most women gain only 1 to 4 pounds total during the first trimester. Nausea, food aversions, and appetite changes make this normal, and some women even lose weight in early pregnancy.

The majority of weight gain happens in the second and third trimesters, when your baby grows fastest and your body builds up the blood volume, fluid, and tissue it needs.

A rough breakdown for a normal weight woman gaining about 30 pounds total:

First trimester: 1 to 4 pounds total
Second trimester: about 1 pound per week
Third trimester: about 1 pound per week (tapering slightly near delivery)

These are averages. Week-to-week fluctuations are common and usually harmless.

Pregnancy Weight Gain by Week

This calculator plots your recommended weight gain by week so you can see a target range at any point in pregnancy. The curve is gentle at first, then steeper during the second and third trimesters.

A few things to keep in mind:

Weight gain per week is not perfectly steady. Water retention, meals, and activity all cause day-to-day changes.
A single weigh-in that falls above or below the curve is not a problem. Trends over several weeks matter more.
If you notice rapid weight gain over a short period (several pounds in a week), mention it to your provider. It can sometimes signal fluid retention or other concerns worth checking.

Weight Gained During Pregnancy if Underweight, Normal Weight, or Obese

Your starting category changes both the total weight gain recommended and the weekly rate.

Underweight women need to gain more to support the growth of the baby and build adequate reserves. The target rate in the second and third trimesters is roughly 1 to 1.3 pounds per week.
Normal weight women aim for about 1 pound per week after the first trimester.
Overweight women target about 0.6 pounds per week in later trimesters.
Obese women have a lower target, around 0.5 pounds per week, because their body already carries energy reserves. This does not mean zero gain. Women who gain too little also face risks.

Teenagers who become pregnant may need to gain at the higher end of their BMI range because their own bodies are still growing. Talk to your health care provider about what makes sense for your age and health.

Where Does Weight During Pregnancy Go

It is reasonable to wonder: if the baby weighs about 7 or 8 pounds at birth, what accounts for the extra pregnancy weight gain?

Here is an approximate breakdown for a woman who gains about 30 pounds:

Baby: 7 to 8 pounds
Placenta: 1.5 pounds
Amniotic fluid: 2 pounds
Uterus growth: 2 pounds
Increased blood volume: 3 to 4 pounds
Breast tissue: 1 to 2 pounds
Extra fluid in tissues: 3 to 4 pounds
Maternal fat stores: 6 to 8 pounds

Maternal fat stores are not wasted weight. Your body sets aside energy to fuel breastfeeding and recovery after delivery. The increased blood volume supports your baby's oxygen supply and the demands of a growing placenta.

Most of this weight is functional. It serves a purpose during pregnancy and begins to reverse after delivery.

What Happens When You Gain Too Much or Too Little Weight

Staying within your recommended weight range is not about vanity. It directly affects the health of both mother and infant.

Risks for Mother and Infant

Gaining too much weight during pregnancy can increase the risk of:

Gestational diabetes
High blood pressure and preeclampsia
Cesarean delivery
A larger-than-average baby (macrosomia), which can complicate delivery
Difficulty losing weight after pregnancy
Higher obesity risk for the child later in life

Gaining too little weight can increase the risk of:

Low birth weight
Preterm delivery
Developmental delays
Difficulty establishing breastfeeding

If you gained too much early on, the answer is not to restrict calories sharply for the rest of pregnancy. Sudden calorie restriction can deprive your baby of nutrients during critical growth periods. Instead, focus on eating healthy, nutrient-dense foods and staying physically active within your provider's guidelines.

Women who are in great shape before pregnancy still need to pay attention to weight gain. Fitness does not eliminate the physiological demands of pregnancy.

Prenatal Nutrition to Help You Gain Weight at a Healthy Rate

What you eat matters as much as how much weight you gain. Prenatal nutrition is about choosing foods that support your pregnancy and your baby's development, not simply eating more.

General guidelines:

You do not need extra calories during the first trimester.
Add about 340 extra calories per day in the second trimester.
Add about 450 extra calories per day in the third trimester.

These are modest increases. A banana with peanut butter and a glass of milk covers the second-trimester bump. Eating for two does not mean doubling your portions.

Calories, Protein, Folate, and Iron

Four nutrients deserve special attention during pregnancy:

Calories: Focus on quality. Choose whole grains, lean proteins, fruits, vegetables, and healthy fats. Avoid filling extra calorie needs with sugary snacks or fast food.
Protein: Supports the growth of the baby and placenta. Aim for about 71 grams per day. Good sources include eggs, poultry, fish (low-mercury types), beans, and dairy.
Folate: Critical in early pregnancy for preventing neural tube defects. Found in leafy greens, fortified cereals, and citrus fruits. Most prenatal vitamins include 400 to 800 micrograms of folic acid.
Iron: Your increased blood volume demands more iron. Lean red meat, spinach, lentils, and fortified cereals are good sources. Pair iron-rich foods with vitamin C to boost absorption.

Foods that are high in nutrients but moderate in calories help you gain weight at a healthy rate without overshooting. If you struggle to eat enough due to nausea, small frequent meals often work better than three large ones.

How to Use This Pregnancy Weight Gain Calculator

The calculator at the top of this page takes a few basic inputs and returns a personalized weight gain timeline.

Calculate Your BMI and Find Your Target Weight

Follow these steps:

Enter your height in feet and inches (or centimeters).
Enter your pre-pregnancy weight. Use the weight you were at before becoming pregnant, not your current weight.
Select your due date or current week of pregnancy.
Indicate whether you're carrying twins or multiples if applicable.
Click calculate.

The tool will:

Calculate your pre-pregnancy BMI
Show your BMI category
Display your total recommended weight gain range
Plot your target weight by week so you can track where you are now

Use your results as a guide. If your current weight falls outside the suggested range, do not panic. Share the results with your health care provider for context.

Weight Gain After Pregnancy: Breastfeeding and Weight Loss

Most women lose about 10 to 13 pounds right away from the baby, placenta, and amniotic fluid. Additional weight comes off gradually over the following weeks and months.

Breastfeeding burns roughly 400 to 500 extra calories per day. Many women who breastfeed find they return to their pre-pregnancy weight faster, though results vary widely.

A few realistic expectations:

It took nine months to gain the weight. Give yourself at least that long to lose it.
Crash dieting while breastfeeding can reduce your milk supply and deprive you of nutrients during recovery.
Physical activity, even moderate walking, helps with both weight loss and postpartum mood.
Some women retain a few pounds permanently after pregnancy, and that is normal.

If you lost weight in early pregnancy due to morning sickness, your overall gain pattern may look different from the standard curve. This is usually not a concern as long as your provider is monitoring your progress.

This Calculator Estimates Weight Gain Goals, Not Medical Advice

This pregnancy weight gain calculator provides estimates based on IOM guidelines, which were developed by the Institute of Medicine of the National Academies. It uses your pre-pregnancy BMI and gestational age to generate a recommended weight range.

It does not replace your health care provider. Every pregnancy has unique factors (medical history, activity level, multiple gestations, pre-existing conditions) that a calculator cannot evaluate.

Use these results as a conversation starter at your next prenatal visit. If you have concerns about gaining too much or too little, your provider can give personalized guidance that accounts for your full picture.