Due Date Calculator

Calculate your estimated pregnancy due date, current gestational week, and trimester milestones based on your last menstrual period (LMP) or conception date.

Calculator Inputs

Select dating criteria.
First day of bleeding of last regular period.
days
Standard menstrual cycle length (default 28 days).

Calculated Results

Estimated Due Date (EDD)
October 24, 2026
Current Gestational Age 12 Weeks, 4 Days
Current Trimester First Trimester (Ending Soon)
Days Remaining Until Delivery 192 Days
Values calculate live as you adjust inputs.

About Due Date Calculator

A pregnancy due date calculator determines the Estimated Date of Delivery (EDD) using Naegele’s rule, assuming a standard 280-day (40-week) gestation period from the first day of the last menstrual period.

What is Due Date Calculator?

A pregnancy due date calculator determines the Estimated Date of Delivery (EDD) using Naegele’s rule, assuming a standard 280-day (40-week) gestation period from the first day of the last menstrual period.

How to Use This Calculator

  1. Select your calculation method (LMP, Conception, or IVF Transfer).
  2. Select the calendar date of the event.
  3. Adjust your personal cycle length if different from 28 days.
  4. View your delivery due date, current trimester, and baby development countdown.

The Mathematical Formula & Variables

EDD = First day of LMP + 1 year - 3 months + 7 days + (CycleLength - 28)

Variables Definition

Symbol / Variable Name Description
280 Days Human Gestation 40 completed gestational weeks from start of menstrual cycle.
Cycle Adjustment Luteal Phase Offset Longer cycles delay ovulation and push due date forward.

Step-by-Step Worked Example

Scenario: LMP started January 17, 2026 with a standard 28-day cycle.

  1. Add 280 calendar days to January 17, 2026.
  2. January 17 + 280 days lands on October 24, 2026.
  3. Gestational age counts forward from January 17, 2026.

Result: Estimated Due Date = October 24, 2026

Frequently Asked Questions

How accurate is the estimated due date?

Only about 4% to 5% of babies are born on their exact due date. However, roughly 85% to 90% arrive within a two-week window (between 37 and 42 weeks of gestation).

What if my ultrasound gives a different date?

First-trimester crown-rump length (CRL) ultrasound scans are the most clinically accurate method for dating pregnancy and will override LMP calculations if discrepancy exceeds 5 to 7 days.