Frequently Asked Questions
How accurate is this HIV risk calculator?
It gives a statistical estimate based on published per-act probabilities and prevalence data, not a diagnosis. It is useful for understanding roughly how much risk an exposure carried and how urgently to act, but it cannot tell you whether transmission actually occurred. Only an HIV test can do that.
Can I get HIV from oral sex?
The risk from oral sex is very low, far lower than anal or vaginal sex, but not exactly zero. Factors like bleeding gums, sores, or ejaculation into the mouth can raise it slightly. If you are worried, testing is always the definitive answer.
What is the window period?
The window period is the time between exposure and when a test can reliably detect HIV. It ranges from about 10 to 33 days for a NAT/RNA test, 18 to 45 days for a 4th-generation lab test, and up to 90 days for some antibody and rapid tests. See our testing guide.
How soon can I get a conclusive result?
A negative 4th-generation lab test at 45 days is highly reassuring, and a negative antibody test at 90 days (3 months) is considered conclusive for that exposure.
I think I was exposed in the last few days. What should I do?
If it has been less than 72 hours and the exposure carried real risk, contact a doctor, emergency department, or sexual health clinic immediately to ask about PEP. PEP can prevent HIV but is time-critical.
What does U=U mean?
Undetectable = Untransmittable. A person with HIV who takes treatment and maintains an undetectable viral load does not transmit HIV to sexual partners. If your partner is durably undetectable, the sexual transmission risk is effectively zero.
Can I get HIV from a needle or sharing injection equipment?
Yes. Sharing injection equipment carries roughly a 0.63% risk per event if the source has HIV, higher than most single sexual exposures. Accidental needlesticks carry a lower but real risk. This calculator now includes these routes.
Does PrEP mean I cannot get HIV?
PrEP taken consistently reduces the risk of getting HIV from sex by about 99%, but it is not 100%, and its protection drops with missed doses. It also does not protect against other STIs.
Is this tool anonymous?
Yes. The calculation runs entirely in your browser. The details you enter are not sent to us or stored anywhere. See our Privacy Policy.
Should I still test if my risk shows as very low?
Testing is the only way to be certain, and regular testing is recommended for anyone who is sexually active. A low estimate is a reason for reassurance, not a substitute for a test if you remain concerned.