Pregnancy Weight Gain Calculator

Modify the values and click the Calculate button to use

Recommended Range: 127.3 – 132.3 lb

Your BMI before pregnancy: 19.4
BMI category: normal
Current week range: 127.3 – 132.3 lb
Delivery range: 145.0 – 155.0 lb
Status: in range

The range is based on Institute of Medicine guidelines and a simplified weekly curve. Your clinician may set a different target for twins, medical conditions, or individual circumstances.

What this pregnancy weight gain calculator does

This calculator estimates a recommended weight range for your current week of pregnancy, based on your pre-pregnancy BMI, whether you are carrying one baby or twins, and the Institute of Medicine weight-gain guidelines. It also shows the range at delivery and whether your current weight is inside the range.

The result is a reference range, not a prescription. Your clinician may set a different target based on your health, the baby's growth, and other factors.

How to use this calculator

Choose US or metric units.
Enter your height.
Enter your weight before pregnancy and your current weight.
Enter your current pregnancy week.
Select whether you are carrying twins.
Click Calculate to see the current and delivery ranges.

The default example is a 5 ft 6 in woman who weighed 120 lb before pregnancy and 130 lb at week 20, with a singleton pregnancy.

Pregnancy weight gain formulas

BMI = pre-pregnancy weight(kg) ÷ height(m)²

Recommended total gain depends on BMI and twins:

Category	Singleton	Twins
Underweight (BMI < 18.5)	28–40 lb	50–62 lb
Normal (18.5–24.9)	25–35 lb	37–54 lb
Overweight (25–29.9)	15–25 lb	31–50 lb
Obese (30+)	11–20 lb	25–42 lb

The weekly curve rises slowly in the first trimester and more quickly from about week 14. The calculator scales the curve to the total range for your category.

What the results mean

BMI before pregnancy: the category used for the range.
Current week range: a recommended weight range for this week.
Delivery range: the expected total range at week 40.
Status: whether your current weight is below, inside, or above the range.

The default example has a pre-pregnancy BMI of 19.4 and a week-20 range of 127.3–132.3 lb, with a delivery range of 145–155 lb.

Assumptions and limitations

The calculator uses a simplified weight-gain curve and the IOM total ranges. It does not account for individual medical conditions, multiple gestations beyond twins, fluid retention, or the baby's growth pattern. It is not a substitute for prenatal care.

Weight gain recommendations are individualized. Discuss any concerns with your obstetric clinician or dietitian rather than changing your diet based on this page alone.

Frequently asked questions

What if my BMI is underweight?

The recommended total gain is higher. The calculator uses the underweight range and scales the weekly curve accordingly.

Does this work for twins?

Yes. Select “Yes” for twins. The total range is wider than for a singleton pregnancy.

Why is my current weight above the range?

A single measurement can reflect fluid, timing of meals, or normal variation. The range is a guide. Discuss the trend with your clinician rather than reacting to one number.

Should I try to lose weight during pregnancy?

No. Pregnancy is not a time for weight loss without medical supervision. Follow your clinician's advice.

Reference tables

Weight gain by week

Week	Recommended Weight Range	Recommended Weight Gain
12	About 2–5 lb total	2–5 lb
20	About 10–14 lb total	8–9 lb since week 12
28	About 17–22 lb total	7–8 lb since week 20
36	About 25–30 lb total	8 lb since week 28
40	About 25–35 lb total	0–5 lb since week 36

Height conversion

Your Height	cm
5 ft 0 in	152
5 ft 4 in	163
5 ft 8 in	173
5 ft 10 in	178

Recommended gain by prepregnancy BMI

Prepregnancy BMI (kg/m 2 )	Category	Total Weight Gain Range	Total Weight Gain Range for Pregnancy with Twins
Below 18.5	Underweight	28–40 lb	37–54 lb
18.5–24.9	Normal weight	25–35 lb	37–54 lb
25.0–29.9	Overweight	15–25 lb	31–50 lb
30.0+	Obese	11–20 lb	25–42 lb

Ranges follow common clinical guidance for singleton and twin pregnancies. Your provider may set a different target based on your health.

Source

References:

Disclaimer

This calculator is for informational and educational purposes only. It is not prenatal care or medical advice. Discuss weight gain and nutrition with a qualified obstetric clinician or dietitian.

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