What is this calculator?
Estimate a conception date from an entered due date.
What can you use it for?
Use it to understand the numerical relationship between the measurements or dates entered. Estimate a conception date from an entered due date.
How to use it
- Enter estimated due date.
- Select Calculate (or Generate for random tools).
- Read the answer and any additional results below the form. Check the units and the limits of the method.
Formula and method
Estimated conception date = supplied due date − 266 days
This approximate date cannot establish the exact day of intercourse or paternity.
Worked example
Estimated due date: 2027-05-01. The result is 8 August 2026 (estimated conception date).
Assumptions and limits
Due date minus 266 days is an estimate. It cannot identify a particular intercourse date or establish paternity.
Frequently asked questions
What inputs does the Conception Calculator need?
Use estimated due date. Read the answer and any additional results below the form. Check the units and the limits of the method.
What assumptions apply to the Conception Calculator?
Due date minus 266 days is an estimate. It cannot identify a particular intercourse date or establish paternity.