Due date and pregnancy week calculator

A date to plan around, with room for uncertainty. Use the due date your maternity care team has given you whenever you have one.

Which date are you using?

Use your care team’s estimated due date, not a scheduled induction or caesarean date.

Care teams may use different due-date conventions. Select only the exact pregnancy age your team uses on that date. If you do not know, or it is different, confirm with them before calculating. This tool does not infer it from your language or location.

This is calendar arithmetic, not a prediction of the day of birth. It does not change the date assigned by your care team.

Starts with today on this device. You can choose another date; the result always shows which date it uses.

Your dates stay in this open page. Nothing is submitted or saved by this tool. Your browser may restore form entries when you go back.

Your dates, clearly explained

Choose a method and add your dates. No result is calculated until you ask.

How the dates are counted

For a regular 28-day cycle, the period-based estimate is 280 calendar days from the first day of the last period (40 weeks). For a supported regular cycle, each day above or below 28 adds or subtracts one day. With an assigned due date, pregnancy age is counted using the exact 40- or 41-week convention you select. Other conventions are not supported.

Pregnancy weeks are counted from the dating baseline, not from a known conception date. This tool does not calculate when conception happened.

Keep your care team's date

A due date is an estimate, not a guaranteed birthday. This calculator cannot confirm pregnancy or replace clinical dating. Uncertain period dates, irregular cycles and variation in ovulation can make a period-based estimate less reliable. An ultrasound or fertility-treatment history may guide your care team's date. For IVF, use the date they assigned.

A result beyond 40 weeks is a calendar count, not advice to wait or a judgment about your pregnancy. Follow your own care plan and contact your maternity care team with questions.

Sources and method

The links explain pregnancy dating and its limits. The 21–35-day cycle range is this tool's scope, following the cited hospital guideline; it does not define which cycles are normal.

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