STI test window calculator and chart
Compare the number of days since an exposure with CDC detection windows and repeat-testing checkpoints. The calculator runs in your browser and does not send your day count to STD Ally.
Private browser calculator
Check the timing
Enter the number of days since the exposure. The number stays in this browser tab and is not added to the URL or analytics.
Enter a day count to compare it with every cited window.
This is a timing reference, not a diagnosis or infection-risk assessment. Do not wait for a window period if you have symptoms or need time-sensitive post-exposure care.
Source-backed data
Testing windows at a glance
| Infection | Test | CDC window or checkpoint | Source |
|---|---|---|---|
| Chlamydia | NAAT at exposed sites | Repeat checkpoint: 1-2 weeks | CDC 2025 nPEP recommendations |
| Gonorrhea | NAAT at exposed sites | Repeat checkpoint: 1-2 weeks | CDC 2025 nPEP recommendations |
| HIV | Lab antigen/antibody test (blood from a vein) | Usually detects at 18-45 days | CDC HIV testing |
| HIV | Antibody test, including most self-tests | Usually detects at 23-90 days | CDC HIV testing |
| HIV | Nucleic acid test (NAT) | Usually detects at 10-33 days | CDC HIV testing |
| Syphilis | Serologic blood testing | Repeat at 4-6 weeks and again at 3 months | CDC 2025 nPEP recommendations |
| Hepatitis B | Hepatitis B surface antigen (HBsAg) | Can appear about 1-12 weeks after exposure | CDC Pink Book: Hepatitis B |
| Hepatitis C | HCV RNA test | RNA usually becomes detectable at 1-2 weeks | CDC hepatitis C diagnosis and testing |
| Hepatitis C | HCV antibody test | Antibodies usually become detectable at 8-11 weeks | CDC hepatitis C diagnosis and testing |
Source review date: August 26, 2026. Detection ranges and repeat-testing checkpoints are different concepts. The table preserves that distinction instead of labeling every endpoint as conclusive.
Questions about STI test timing
What is an STI test window period?
A window period is the time between an exposure and when a particular test can usually detect an infection. The timing depends on the infection, specimen, and test technology.
Does a negative result mean I am clear?
Not necessarily. A negative result can need repeating when testing happened before the end of a cited window, when a different exposed site was not tested, or when a clinician recommends follow-up for the specific exposure.
Does this calculator store my exposure information?
No. It asks only for a number of days, keeps that number in the current browser tab, and does not add it to the URL, storage, or analytics.
Should I wait for the window period if I have symptoms?
No. Seek a clinician evaluation now if you have symptoms. If a possible HIV exposure was within 72 hours, seek time-sensitive medical advice about post-exposure prophylaxis instead of waiting to test.
Sources: CDC HIV testing windows · CDC 2025 nPEP recommendations · CDC hepatitis C testing · CDC Pink Book: Hepatitis B.
This page is a decision aid - general information, not medical advice. See methodology for how we rank options and our editorial policy for source and review standards.
Researchers and educators may cite this compilation by linking to this page. See the editorial policy for source and correction standards.