Pregnancy Test Timing Calculator
When your test can detect hCG, by test sensitivity. Free, private and instant.
How to use the Pregnancy Test Timing
- Pick date of ovulation or unprotected sex.
- Choose sensitivity of your test (mIU/mL): 10 mIU/mL (early detection tests), 20 mIU/mL (sensitive), 25 mIU/mL (most common) or 50 mIU/mL (older or basic).
- Press Calculate to get an instant result with a colour scale, chart and plain-English explanation.
About the Pregnancy Test Timing
Home pregnancy tests detect the hormone hCG, which rises quickly after implantation. Enter the date of ovulation or sex and your test’s sensitivity to see the earliest day it is likely to turn positive and when a result becomes reliable.
Also known as: when to test for pregnancy, pregnancy test day calculator, hCG test timing, days past ovulation test.
Worked example
Dates in this example are worked out as if today were 5 Nov 2026.
- Date of ovulation or unprotected sex: 27 Oct 2026
- Sensitivity of your test (mIU/mL): 25 mIU/mL (most common)
Days until your test can detect pregnancy: 4 days (Earliest 9 Nov 2026 · reliable 11 Nov 2026). A 25 mIU/mL test is expected to turn positive about 13 days after ovulation (9 Nov 2026), and is most reliable from 11 Nov 2026. Today is 9 days after your date.
- Earliest possible positive: 9 Nov 2026
- Reliable result from: 11 Nov 2026
- Best day (period due): 10 Nov 2026
- Days after ovulation today: 9
Formula and cut-offs
hCG roughly doubles every 48 hours. Typical level (mIU/mL) = 10 x 1.45^(days after ovulation - 10). A test turns positive when hCG exceeds its sensitivity: 10, 20, 25 or 50 mIU/mL.
Frequently asked questions
What is a 25 mIU/mL pregnancy test?
The lowest hCG level at which the test turns positive. Lower numbers detect pregnancy earlier.
Can I get a false negative?
Yes, if you test too early, drink a lot beforehand or ovulated later than you thought. Retest after 2 to 3 days.
When is the most reliable day?
From the day your period is due, or a week later for the highest accuracy.
Sources and references
- ACOG Committee Opinion 700 - Methods for estimating the due date
- Institute of Medicine (2009) - Weight Gain During Pregnancy: Reexamining the Guidelines
- NHS - Pregnancy guide
Written and checked by the MediHub editorial team against the sources above. Read how we build and review our calculators.
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Last updated . This calculator is for education only and is not medical advice. See the medical disclaimer.