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Health & fitness

Due date calculator

Due date calculator: enter your values and get an instant free result.

Your result

Complete the fields and calculate.

Calculation method and formula

First day of last period + 280

Understand the inputs

First day of last period
Enter a valid calendar date. Start/end-day conventions are explained below.

Assumptions and limitations

The calculation starts on the first day of the last period and uses the 280-day rule. Cycle length, ultrasound and individual circumstances can change clinical dating.

The formula uses the specified units. Displayed numbers are rounded; whole packs, item counts and full time periods may also be rounded within the calculation.

Worked example

Illustrative values. Replace them with your own inputs for your calculation.

First day of last period
2026-07-01
Example resultApril 7, 2027

Guide based on the 280-day rule; only a small share of births occur on the exact date.

Model revision: October 17, 2026 · How CleverCalc works

FAQ

Frequently asked questions

How does Due date calculator work?+

First day of last period + 280. The calculation starts on the first day of the last period and uses the 280-day rule. Cycle length, ultrasound and individual circumstances can change clinical dating.

What assumptions should I consider for this result?+

The calculation starts on the first day of the last period and uses the 280-day rule. Cycle length, ultrasound and individual circumstances can change clinical dating. The formula uses the specified units. Displayed numbers are rounded; whole packs, item counts and full time periods may also be rounded within the calculation.

How accurate is the result?+

The formula uses the specified units. Displayed numbers are rounded; whole packs, item counts and full time periods may also be rounded within the calculation. Health values are general information, not a diagnosis or personal treatment recommendation.

Is this calculator free?+

Yes. Calculations and PDF export work without an account or registration.

What happens to my inputs?+

Calculations run in your browser. Results are saved locally only when you add them to My results; favourites and history are also local. Shared links contain your values. The currency tool requests the selected currencies from its rate provider without sending your amount.

Toolbox

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