How accurate is the estimate?
It's as good as the published averages it's built on, and those come with wide uncertainty. Real risk depends on things the calculator can't see, like your partner's exact viral load. Use it to judge how urgently to act. Only a test tells you whether you have HIV.
I had a possible exposure in the last few days. What should I do?
If it's been less than 72 hours and the risk was significant, go to an emergency department, urgent care, or sexual health clinic today and ask about PEP. It works best the sooner it starts. Don't wait for a test: no test can detect a new infection this early.
Can you get HIV from oral sex?
It's possible but rare. CDC rates the risk as low, and documented cases are few. Risk rises a little with ejaculation in the mouth, bleeding gums, mouth ulcers, or another STI.
Can I get HIV from kissing, saliva, or a toilet seat?
No. HIV isn't passed on through saliva, sweat, tears, kissing, sharing food or drinks, toilets, or insect bites. It needs blood, semen, pre-seminal fluid, rectal or vaginal fluids, or breast milk to get into the bloodstream or through a mucous membrane.
Does ethnicity affect HIV risk?
Not biologically. The chance of HIV passing during sex or through blood is the same for everyone. What differs is how common HIV is in different communities, for social and economic reasons. That changes the chance that a partner of unknown status has HIV, so where official figures exist (currently the UK and US) you can add their community.
What is the window period?
The time between an infection and when a test can detect it. It's about 10 to 33 days for a NAT, 18 to 45 days for a lab antigen/antibody test, and up to 90 days for rapid and home antibody tests. A negative result is only conclusive after the window closes.
When can I trust a negative result?
A negative lab antigen/antibody test (blood from a vein) at 45 days, or any HIV test at 90 days, rules out HIV from that exposure, as long as there were no newer exposures. If you took PEP, follow your clinician's testing schedule.
Do home self-tests work?
Yes, approved self-tests are accurate, but most are antibody tests, so they're only conclusive 90 days after an exposure. A positive self-test always needs a follow-up lab test to confirm it.
What does U=U mean?
Undetectable = untransmittable. A person with HIV who takes treatment and keeps an undetectable viral load does not pass HIV on through sex. This is backed by large studies of couples.
If I'm on PrEP, can I still get HIV?
It's very unlikely if you take it as prescribed: PrEP lowers the risk from sex by about 99%. Protection drops if doses are missed. Keep up the regular HIV tests that come with PrEP.
I have symptoms. Does that mean I have HIV?
Not necessarily. Early HIV can cause fever, rash, sore throat or swollen glands, but so can many common infections, and many people with HIV have no symptoms at all. Anxiety can also cause real physical symptoms. If you're worried, get a test that can detect early infection.
My estimate is very low. Should I still test?
If it will put your mind at rest, yes. Testing is quick, usually free, and the only way to be certain. CDC also recommends that everyone aged 13 to 64 test for HIV at least once.
Is anything I enter stored or shared?
No. The calculation runs entirely in your browser. Nothing you type is sent to a server, saved, or tracked, and closing the page clears it.