Pregnancy Weight Gain Week by Week: Calculator & Chart

How much weight should you gain during pregnancy — and when? A pregnancy weight gain calculator week by week helps you track whether you’re on target based on your pre-pregnancy BMI. For nutrition guidance to support healthy gain, see our what to eat in the first trimester and pregnancy safe foods list guides. This article includes ACOG-recommended weight gain charts for all four BMI categories, a week-by-week breakdown showing expected cumulative gain, and a detailed look at exactly where all that weight goes. Use our interactive weight gain calculator alongside these charts for personalized tracking.

📌 Key Takeaway: The pregnancy weight gain calculator week by week shows that most gain happens in the second and third trimesters (about 1 pound per week for normal-weight women). Total recommended gain ranges from 11-40 pounds depending on your pre-pregnancy BMI. Gaining within the recommended range lowers the risk of complications for both you and baby.

ACOG Recommended Total Weight Gain by BMI Category

The American College of Obstetricians and Gynecologists (ACOG) sets weight gain guidelines based on your pre-pregnancy Body Mass Index (BMI). These recommendations are designed to optimize outcomes for both mother and baby.

Pre-Pregnancy BMI Category	BMI Range	Recommended Total Gain	Rate in 2nd & 3rd Trimester
Underweight	Below 18.5	28-40 lbs (12.5-18 kg)	~1.0-1.3 lbs/week
Normal weight	18.5-24.9	25-35 lbs (11.5-16 kg)	~0.8-1.0 lbs/week
Overweight	25.0-29.9	15-25 lbs (7-11.5 kg)	~0.5-0.7 lbs/week
Obese (all classes)	30.0 and above	11-20 lbs (5-9 kg)	~0.4-0.6 lbs/week

⚠️ Important: These are ACOG guidelines for singleton pregnancies. If you’re carrying twins, your recommended gain is higher: 37-54 lbs (normal weight), 31-50 lbs (overweight), or 25-42 lbs (obese). Always discuss your target with your provider.

Pregnancy Weight Gain Calculator Week by Week: Complete Chart

This is the core reference table. It shows the expected cumulative weight gain at key weeks for all four BMI categories. Use this pregnancy weight gain calculator week by week chart to see exactly where you should be at each stage.

Week	Month	Trimester	Underweight (lbs)	Normal Weight (lbs)	Overweight (lbs)	Obese (lbs)
4	1	1st	0-1	0-1	0-1	0-0.5
8	2	1st	1-3	1-2	0.5-2	0-1
12	3	1st	2-5	2-4	1-3	0.5-2
16	4	2nd	5-9	4-8	3-6	2-4
20	5	2nd	9-14	8-12	5-9	3-7
24	6	2nd	14-19	12-17	7-13	5-9
28	7	3rd	18-25	16-21	9-16	6-12
32	8	3rd	22-31	19-26	11-19	8-14
36	9	3rd	25-36	22-31	13-22	9-17
40	10	3rd	28-40	25-35	15-25	11-20

📊 Key Data: According to ACOG, only about one-third of pregnant women gain within the recommended range. Approximately 48% gain more than recommended, and 21% gain less. Both extremes are associated with increased risks — excessive gain raises the risk of gestational diabetes, preeclampsia, and cesarean delivery, while insufficient gain is linked to preterm birth and low birth weight.

Weight Gain by Trimester: What to Expect

The pattern of weight gain matters almost as much as the total amount. Here’s what the pregnancy weight gain calculator week by week data shows for each trimester.

First Trimester (Weeks 1-13)

Expected Total Gain	Rate	Notes
1-5 lbs (0.5-2.3 kg)	Very slow	Minimal weight gain is normal; some women lose weight due to morning sickness

Weight gain in the first trimester is minimal for all BMI categories. Many women gain only 1-4 pounds total — and some actually lose weight due to nausea and food aversions. This is completely normal and not a cause for concern unless weight loss is severe (more than 5% of pre-pregnancy weight).

Second Trimester (Weeks 14-27)

BMI Category	Expected Gain This Trimester	Avg. Weekly Rate
Underweight	12-14 lbs	~0.9-1.1 lbs/week
Normal weight	10-13 lbs	~0.8-1.0 lbs/week
Overweight	6-10 lbs	~0.5-0.7 lbs/week
Obese	4-7 lbs	~0.3-0.5 lbs/week

The second trimester is when steady, consistent weight gain begins. Your appetite typically returns as nausea subsides, and baby is growing rapidly. This is the most important period for establishing a healthy gain pattern.

Third Trimester (Weeks 28-40)

BMI Category	Expected Gain This Trimester	Avg. Weekly Rate
Underweight	14-16 lbs	~1.0-1.3 lbs/week
Normal weight	12-14 lbs	~0.9-1.1 lbs/week
Overweight	8-12 lbs	~0.6-0.9 lbs/week
Obese	5-8 lbs	~0.4-0.6 lbs/week

Weight gain may slow or plateau in the final 2-3 weeks before delivery as baby “drops” into the pelvis. This is normal and not a sign of problems.

💡 Tip: Use our weight gain calculator to get a personalized week-by-week target based on your exact pre-pregnancy weight and height. Tracking consistently helps you and your provider catch any concerns early.

Where Does the Weight Go? Complete Breakdown

One of the most common questions is “where does all this weight go?” The answer: most of it supports baby’s growth and your body’s preparations for birth and breastfeeding.

Component	Weight at Term	Percentage
Baby	6.5-8.5 lbs (3-3.9 kg)	25-27%
Placenta	1.5 lbs (0.7 kg)	5%
Amniotic fluid	2 lbs (0.9 kg)	6%
Uterus growth	2 lbs (0.9 kg)	6%
Breast tissue growth	1-3 lbs (0.5-1.4 kg)	3-10%
Increased blood volume	3-4 lbs (1.4-1.8 kg)	10-13%
Extra body fluid	3-4 lbs (1.4-1.8 kg)	10-13%
Maternal fat stores	6-8 lbs (2.7-3.6 kg)	19-27%
Total	25-35 lbs	100%

📊 Key Data: The maternal fat stores (6-8 lbs) serve a critical biological purpose — they provide energy reserves for breastfeeding. Women who breastfeed exclusively tend to lose these stores within 6-12 months postpartum. Your body gains this fat intentionally, primarily in the hips, thighs, and back.

When to Worry About Weight Gain

While the pregnancy weight gain calculator week by week provides guidelines, there are situations that warrant a conversation with your healthcare provider.

Signs of Too-Rapid Weight Gain

• Gaining more than 3 pounds in one week (especially in second or third trimester)
• Sudden swelling in face, hands, or feet (could indicate preeclampsia)
• Consistently gaining above the recommended range for your BMI category
• Blood pressure rising alongside weight gain

Signs of Insufficient Weight Gain

• Not gaining any weight by week 20
• Losing weight in the second or third trimester
• Gaining less than 1 pound per month in the second or third trimester (for normal-weight women)
• Baby measuring small for gestational age on ultrasound

⚠️ Important: Normal daily weight fluctuations of 1-3 pounds are caused by water retention, digestion, and sodium intake. Don’t panic about day-to-day changes. Weekly averages are much more meaningful. Weigh yourself at the same time each day (ideally morning, after using the bathroom) for the most consistent tracking.

Tips for Healthy Weight Gain by Trimester

Trimester	Calorie Increase Needed	Key Focus
First	0 extra calories	Focus on nutrient quality, not quantity. Eat what you can tolerate through nausea
Second	~340 extra calories/day	Steady gain begins. Add nutrient-dense snacks — Greek yogurt, nuts, avocado
Third	~450 extra calories/day	Baby growing rapidly. Prioritize protein (71g/day), calcium, iron, and DHA

These calorie recommendations come from the ACOG and apply to normal-weight women with singleton pregnancies. Your provider may adjust them based on your BMI category and activity level.

How to Use the Weight Gain Calculator for Your Pregnancy

1. Determine your pre-pregnancy BMI — use our weight gain calculator to enter your height and pre-pregnancy weight
2. Find your BMI category in the table above (underweight, normal, overweight, or obese)
3. Check the week-by-week chart to see the expected cumulative gain at your current week
4. Track weekly — weigh yourself once per week at the same time for consistent data
5. Discuss with your provider at each prenatal visit — they plot your gain on a growth curve

The pregnancy weight gain calculator week by week is a guide, not a strict rule. Every pregnancy is different, and what matters most is the overall trend rather than hitting an exact number each week.

FAQ

How much weight should I gain per week during pregnancy?

For normal-weight women, the pregnancy weight gain calculator week by week shows a recommended rate of about 0.8-1.0 pounds per week during the second and third trimesters, with minimal gain (1-5 lbs total) in the first trimester. Overweight women should aim for 0.5-0.7 lbs/week, and underweight women for 1.0-1.3 lbs/week.

What if I’m gaining too much weight during pregnancy?

If you’re consistently above the recommended range from the pregnancy weight gain calculator week by week chart, talk to your provider. They may recommend increasing physical activity (walking, swimming, prenatal yoga), choosing more nutrient-dense foods, reducing empty calories from sugary drinks and snacks, and meeting with a registered dietitian for a personalized plan.

Is it normal to lose weight in the first trimester?

Yes, mild weight loss (up to 5% of pre-pregnancy weight) in the first trimester is common and not harmful. Morning sickness, food aversions, and changes in appetite can reduce caloric intake. Most women regain this weight in the second trimester. Consult your provider if you lose more than 5% of your body weight or can’t keep fluids down.

Does pregnancy weight gain affect the baby?

Yes. Gaining within the ACOG-recommended range is associated with the best outcomes for both mother and baby. Excessive gain increases the risk of gestational diabetes, preeclampsia, cesarean delivery, and a larger baby (macrosomia). Insufficient gain is linked to preterm birth, low birth weight, and developmental concerns.

References

• American College of Obstetricians and Gynecologists. “Weight Gain During Pregnancy.” Committee Opinion No. 548. acog.org
• Institute of Medicine. “Weight Gain During Pregnancy: Reexamining the Guidelines.” nationalacademies.org
• Mayo Clinic. “Pregnancy Weight Gain: What’s Healthy?” mayoclinic.org
• Centers for Disease Control and Prevention. “Weight Gain During Pregnancy.” cdc.gov

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