Why it exists
After a possible exposure, people tend to search late at night and find either alarming stories or vague reassurance. Neither helps. What helps is a realistic sense of the risk, knowing whether PEP is worth seeking, and knowing when a test can give a reliable answer. This tool tries to provide all three in a few minutes.
What it does
- Estimates the chance that a described exposure resulted in HIV
- Shows exactly which factors produced that number, and what would lower it
- Flags when PEP may still be possible
- Lays out which tests work on which day, and when a negative result becomes conclusive
- Lets you print a summary to take to a clinic, or add test dates to your calendar
Where the numbers come from
Per-act transmission estimates, test window periods and PrEP effectiveness come from the US Centers for Disease Control and Prevention. Country prevalence figures are UNAIDS estimates. Where we've had to make an assumption, such as how much PEP timing matters, we say so on the methodology page.
What it isn't
It isn't a diagnosis, a substitute for a clinician, or a reason to skip testing. A low number doesn't mean you can't have HIV, and a high number doesn't mean you do. If you're worried, get tested.
Privacy by design
The calculator runs entirely in your browser, and nothing you enter is sent anywhere. There are no accounts. We count visits with cookieless analytics, and use Google Analytics cookies only if you allow them.Read the privacy policy.