DueDateCalculator.ai

Pregnancy timing

Conception Date Calculator

Estimate the date you likely conceived from the first day of your last period — along with your fertile window and due date.

Your details

The first day bleeding started.

Days from one period to the next. Default 28.

Calculated on your device. Your dates are never sent or stored.

Enter your details to see your estimate. Every result is an estimate — your clinician sets the official due date.

How it works

Conception usually happens around ovulation, roughly two weeks after the first day of your last period on a typical cycle. This tool estimates that date and the fertile window around it.

If your cycles run longer or shorter than 28 days, enter your average — ovulation, and the conception estimate, shift with it.

See the full methodology and pregnancy term definitions on the main page.

The formula
conception ≈ LMP + 14 days (ovulation)due date = LMP + 280 days

More calculators

Due Date CalculatorEstimate your due date from your last period, conception, or IVF transfer. Pregnancy Week CalculatorSee how far along you are in weeks and days. IVF Due Date CalculatorDue date from your embryo transfer date and embryo age. Reverse Due Date CalculatorWork back from a due date to your last period and conception. Gestational Age CalculatorGestational age for any date you choose.