How this calculator works
The regular-cycle calendar method estimates the next period and suggests testing one day later. The possible early date is ten days after estimated ovulation, using a fixed 14-day luteal phase. This is a date estimate for home urine tests, not a prediction of test accuracy: early tests can be negative during pregnancy, and test sensitivity and actual ovulation vary. A positive result or ongoing uncertainty needs clinical follow-up. The result is an estimate for information only and is not medical advice.
Formula
Period due = LMP + cycle days. Suggested test date = period due + 1 day. Earliest estimate = LMP + cycle - 14 + 10 days.
Worked example
For LMP 2026-01-08 and a 28-day cycle, the expected period is February 5, suggested testing is February 6, and possible early detection is February 1.
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Frequently asked questions
Does a negative early test rule out pregnancy?
No. Follow the test instructions for repeat testing and seek clinical advice if the period remains absent.
Is the early date reliable for irregular cycles?
No. This calendar method assumes regular cycles and cannot identify actual ovulation or implantation.
What does the earliest test date assume?
A 14-day luteal phase and implantation ten days after ovulation. A longer luteal phase pushes the date later.