Due
Date
Calculator

Calculate your estimated due date, gestational age, trimester timeline, and pregnancy milestones from your last menstrual period.

Input

Estimated Due Date

Your baby is due

Jul 20, 2027

Gestational Age0 weeks, 0 days
Estimated ConceptionOct 27, 2026
Current Trimester1st Trimester

How It Works

This calculator uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP) to estimate your due date.

If your cycle length differs from 28 days, the estimate adjusts accordingly. A longer cycle shifts the due date later; a shorter cycle shifts it earlier.

This calculator provides estimates only. Actual due dates may vary. Consult your healthcare provider for personalized guidance.

Trimester Breakdown

1st TrimesterWeeks 1–12
Oct 13, 2026 – Jan 11, 2027
2nd TrimesterWeeks 13–26
Jan 12, 2027 – Apr 19, 2027
3rd TrimesterWeeks 27–40
Apr 20, 2027 – Jul 20, 2027

Key Milestones

First Heartbeat Detectable~Week 6
Nov 24, 2026
End of First Trimester~Week 12
Jan 5, 2027
First Fetal Movement~Week 18
Feb 16, 2027
Viability Milestone~Week 24
Mar 30, 2027
Third Trimester Begins~Week 27
Apr 20, 2027
Full Term~Week 37
Jun 29, 2027

Learn more

How do cycle trackers predict ovulation, and why do cycle lengths vary?

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Frequently Asked Questions

The most common method is Naegele rule: add 280 days (40 weeks) to the first day of the last menstrual period. This estimate assumes a regular 28-day cycle and ovulation on day 14.

Only about 5 percent of babies are born on their estimated due date. Most deliveries occur within two weeks before or after the due date, giving a normal delivery window of 38 to 42 weeks gestation.

Gestational age is counted from the first day of the last menstrual period and is the standard used by doctors. Fetal age starts from conception, which is approximately two weeks after the last period, making it two weeks less than gestational age.

Due Date Calculator - Pregnancy Due Date Estimator | ToolsCanvas