Pregnancy Calculator

Q: How do I know which trimester I am in?

The calculator uses estimated gestational age. The first trimester continues through 13 weeks and 6 days, the second through 27 weeks and 6 days, and the third begins at 28 weeks.

Q: Is an ultrasound due date more accurate?

Early ultrasound dating can be especially useful when the last menstrual period is uncertain or menstrual cycles are irregular. A healthcare professional may use ultrasound findings to establish or confirm the official due date.

Estimate your due date, pregnancy week, trimester, and pregnancy progress instantly.

Enter Your Pregnancy Details

Calculation Method

First Day of Your Last Period

Average Cycle Length

Enter the average number of days in your menstrual cycle. The standard cycle length is 28 days.

Your Pregnancy Result

— Estimated Due Date

Gestational Age —

Trimester —

Estimated Conception Date —

Gestational Age in Days —

Time Until Due Date —

Pregnancy Progress —

Pregnancy Progress 0%

How Does This Pregnancy Calculator Work?

Choose either your last menstrual period or conception date, then enter the requested information. The calculator estimates your due date, current gestational age, trimester, conception date, and pregnancy progress.

Pregnancy Due Date Calculation

Standard Pregnancy Dating

LMP Method: Estimated Due Date = LMP + 280 days + (Cycle Length − 28 days)
Conception Method: Estimated Due Date = Conception Date + 266 days

When using the LMP method, the calculator adjusts the estimated due date by the difference between your average cycle length and the standard 28-day cycle.

Pregnancy Weeks and Trimesters

Pregnancy is normally dated from the first day of the last menstrual period. The first trimester lasts through 13 weeks and 6 days, the second trimester runs from 14 weeks through 27 weeks and 6 days, and the third trimester begins at 28 weeks.

How Accurate Is a Pregnancy Due Date?

A pregnancy due date is an estimate rather than a guaranteed delivery date. Dating can be less certain when menstrual cycles are irregular or the last menstrual period is unknown. An early ultrasound can help establish or confirm pregnancy dating.

Important: This pregnancy calculator provides general estimates for informational purposes only. It does not replace medical advice, prenatal care, or ultrasound dating. If your healthcare professional gives you an official due date, use that date for your medical care.

Frequently Asked Questions

Can my due date change during pregnancy?

Yes. A due date calculated from your last menstrual period or conception date is an estimate. Your healthcare professional may revise it if an early ultrasound provides more reliable pregnancy dating, especially when your cycle is irregular or the date of your last period is uncertain.

What if my menstrual cycle is not 28 days?

Enter your average cycle length in the calculator. The estimated due date will be adjusted according to the difference between your cycle length and the standard 28-day cycle.

Can I calculate my due date from conception?

Yes. Select Conception Date as the calculation method and enter your estimated conception date. The calculator adds approximately 266 days to estimate the due date.

How do I know which trimester I am in?

The calculator uses your estimated gestational age to show your current trimester. The first trimester continues through 13 weeks and 6 days, the second through 27 weeks and 6 days, and the third begins at 28 weeks.

Is an ultrasound due date more accurate?

Early ultrasound dating can be especially useful when the date of the last menstrual period is uncertain or menstrual cycles are irregular. Your healthcare professional may use ultrasound findings to establish or confirm your official due date.