Lunia · Free tools
Pregnancy Test Calculator
Find a testing date using the NHS 21-day guidance when your next period is unknown.
Your details
Runs entirely in your browser. Nothing you type is sent anywhere or saved.
Your result
Ready to calculate
Enter your details, then calculate to see your result here.
How this calculator works
When the expected period date is unknown, the calculator adds 21 calendar days to the date of the last unprotected sex. If you supply an expected period date, it also shows that date because most tests can be used from the first day of a missed period.
A worked example
Date of the last unprotected sex: Aug 1, 2026 · Expected period date, if known: Aug 24, 2026
- Testing date when the next period is unknown
- Aug 22, 2026
- If your expected period date is known
- Test from Aug 24, 2026 if your period has not started.
These are illustrative inputs, not personal recommendations.
Common questions
What if there was unprotected sex on several dates?
Use the most recent date for the 21-day guidance. A negative test taken too early may not rule out pregnancy from the later date.
How should I use the result?
This tool does not calculate pregnancy probability or detect pregnancy. Follow your test instructions. If a result is negative but your period remains absent, repeat after a few days and seek advice if you are concerned.
Sources & method references
Formula-based results are estimates, not individual medical advice.