What does the Due Date Calculator work out?

Estimated due date from your last period. It is one of the Health & Fitness tools on Mondo Knows.

How is the Due Date Calculator calculated?

The maths is short enough to check by hand: Due date = last menstrual period + 280 days.

Do I need to sign up, and is my data stored?

No sign-up, and nothing you type is sent anywhere. The calculation runs in your own browser, so the figures stay on your device and the page works offline once loaded.

Mondo Knows Tools

Due Date Calculator

Estimated due date from your last period. Use the free due date calculator below to get an instant answer, with the formula shown so you can check the maths and trust the result. Free, private, and no sign-up.

First day of last period

Average cycle length

days

Mondo says

Choose the first day of your last period.

The formula

Due date = last menstrual period + 280 days

Due Date Calculator: common questions

What does the Due Date Calculator work out?: Estimated due date from your last period. It is one of the Health & Fitness tools on Mondo Knows.
How is the Due Date Calculator calculated?: The maths is short enough to check by hand: Due date = last menstrual period + 280 days.
Do I need to sign up, and is my data stored?: No sign-up, and nothing you type is sent anywhere. The calculation runs in your own browser, so the figures stay on your device and the page works offline once loaded.

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Estimates for general guidance only. This is not financial, medical or legal advice. Everything runs in your browser and nothing you type is stored.