Calculator Comparison

Pregnancy BMI Calculator vs Pregnancy Week Calculator

Not sure which calculator to use? Here's a side-by-side comparison of the Pregnancy BMI Calculator and Pregnancy Week Calculator to help you pick the right one for your needs.

Pregnancy BMI Calculator

Pregnancy & Baby

Calculate your BMI before and during pregnancy with recommended weight gain ranges based on your starting BMI.

What you enter

Height
Pre-Pregnancy Weight

What you get

Pre-Pregnancy BMI(primary)
BMI Category
Recommended Total Gain
Current Weight Gain
Weight Gain Status

Use Pregnancy BMI Calculator

Pregnancy Week Calculator

Pregnancy & Baby

Calculate exactly how many weeks and days pregnant you are based on your last menstrual period or estimated due date.

What you enter

First Day of Last Period

What you get

Weeks and Days Pregnant(primary)
Current Trimester
Estimated Due Date
Pregnancy Progress

Use Pregnancy Week Calculator

Key Differences

Feature	Pregnancy BMI Calculator	Pregnancy Week Calculator
Category	Pregnancy & Baby	Pregnancy & Baby
Inputs	2 required fields	1 required fields
Outputs	5 results	4 results
Chart	No chart	No chart
FAQs	3 answered	3 answered

Input Comparison

Only in Pregnancy BMI Calculator

Height
Pre-Pregnancy Weight
Current Weight (optional)
Weeks Pregnant (optional)

Only in Pregnancy Week Calculator

First Day of Last Period

Which Calculator Should You Use?

Use the Pregnancy BMI Calculator if you need to:

Calculate pre-pregnancy bmi
When you know your height and pre-pregnancy weight

Use the Pregnancy Week Calculator if you need to:

Calculate weeks and days pregnant
When you know your first day of last period

Frequently Asked Questions

How much weight should I gain during pregnancy?

Recommended gain depends on pre-pregnancy BMI. Underweight: 28-40 lbs. Normal weight: 25-35 lbs. Overweight: 15-25 lbs. Obese: 11-20 lbs. Multiple pregnancies require more gain. Consult your doctor.

When do you gain the most weight in pregnancy?

Weight gain is minimal in the first trimester (1-5 lbs total). Gain accelerates in the second and third trimesters, averaging about 1 pound per week for normal-weight women.

How do I count pregnancy weeks?

Count from the first day of your last menstrual period (LMP). If your LMP was January 1 and today is February 12, you're about 6 weeks pregnant. Your doctor counts the same way.

Why does pregnancy start before conception?

Pregnancy is dated from the LMP because most women know this date reliably. Conception usually occurs about 2 weeks later. This is why at 4 weeks pregnant, the embryo is about 2 weeks old.

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Bottom Line

Choose the Pregnancy BMI Calculator if you need to calculate pre-pregnancy bmi. Use the Pregnancy Week Calculator if you need to calculate weeks and days pregnant. Both calculators are free and require no sign-up.

Use Pregnancy BMI Calculator Use Pregnancy Week Calculator

Feature

Pregnancy BMI Calculator

Pregnancy Week Calculator