Dela Tools · runs on your device

Due date calculator

Estimate a due date from your last period and usual cycle length. This calendar calculation cannot confirm a pregnancy or replace clinical dating.

Your dates

First day of your last period

Average cycle length

Days from one period start to the next

Your estimate

Enter your dates to see an estimate.

Estimated due date—· estimated

Estimated week from these inputs—· estimated

Second trimester begins—· estimated

Third trimester begins—· estimated

A due date is an estimate, not a predicted delivery day. Use the date established by your care team.

How this is calculated

This tool uses a cycle-adjusted calendar model: due date = last period + 280 days + (cycle length − 28). It assumes that the cycle-length difference shifts the dating estimate; that assumption may not fit your pregnancy.

To keep the outputs consistent, the estimated week and trimester dates count from 280 days before that calculated due date. The second trimester starts at 14 weeks 0 days and the third at 28 weeks 0 days, following ACOG's trimester definitions. Following these definitions keeps the math consistent with clinical convention; a clinician's dating still leads.

An estimate, not medical advice. Your clinician establishes pregnancy dates using the relevant menstrual, ultrasound and treatment information. See ACOG's guidance on pregnancy dating. This tool is not designed for dating an assisted-reproduction pregnancy.

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