Due Date Calculator

Estimate your pregnancy due date based on last menstrual period, conception, or ultrasound. This tool uses standard medical calculations for reference.

Weeks and days
Estimated Due Date:
Current Gestational Age:

How to Use This Due Date Calculator

Select the method you prefer, enter the required date and click “Calculate Due Date”. The calculator instantly shows your estimated due date, current gestational age and, when using LMP, your fertile window.

Last Menstrual Period – Naegele’s Rule

The most common method. Assumes a 28-day cycle with ovulation on day 14.

Due Date = LMP + 280 days
or
LMP + 1 year − 3 months + 7 days
Example

LMP: March 10, 2025
→ March 10, 2026 − 3 months = December 10, 2025
→ + 7 days = December 17, 2025

Conception Date Method

When conception date is known (IVF, ovulation kits):

Due Date = Conception Date + 266 days (38 weeks)

Ultrasound Dating

Most accurate in the first trimester (±5–7 days).

Remaining days = 280 − (weeks × 7 + days at scan)
Due Date = Ultrasound date + Remaining days

Accuracy Comparison

MethodAccuracyBest for
First trimester ultrasound±5–7 daysMost accurate
Known conception (IVF)±1–2 daysExact date known
LMP (regular cycles)±10–14 daysRegular cycles
LMP (irregular cycles)±21+ daysLeast reliable

Pregnancy Timeline & Trimesters

First Trimester (1–12 weeks): Organ formation, heartbeat at 6–7 weeks.

Second Trimester (13–27 weeks): Baby movements felt, anatomy scan.

Third Trimester (28–40+ weeks): Rapid growth, full-term from 37 weeks.

Frequently Asked Questions

Only 4–5% of babies are born on their exact due date. 60% arrive within ±1 week, 90% within ±2 weeks.

If an early ultrasound differs by more than 7 days from LMP, doctors usually the ultrasound date is used.

For cycles longer/shorter than 28 days, add/subtract the difference to the LMP result.