How this calculator works
Although this page is titled “aids risk calculator,” the estimate is specifically about HIV transmission risk from a given exposure. AIDS is a later stage of untreated HIV, so the first clinical question after exposure is HIV risk and testing.
The calculator uses published per-exposure averages and adjusts them based on the details you enter, such as partner status, barrier use, PrEP, and timing of PEP. The final result is an educational estimate—not a diagnosis.
Factors that change HIV transmission risk
1) Type of exposure
Different exposures carry different baseline probabilities. Receptive anal sex and sharing injection equipment are generally higher-risk than oral exposure.
2) Partner/source HIV status and viral load
Risk depends heavily on whether the source has HIV and whether they are on effective treatment. People with sustained undetectable viral load do not sexually transmit HIV (U=U).
3) Prevention tools
- Condoms/barriers reduce risk when used correctly and consistently.
- PrEP dramatically lowers risk for sexual exposure when adherence is high.
- PEP can reduce risk if started as soon as possible, ideally within 72 hours.
4) Co-existing STI or inflammation
STIs and genital inflammation can increase susceptibility and infectiousness, which is why regular STI screening is part of HIV prevention.
What to do after a possible exposure
- If exposure was within 72 hours, seek urgent medical care and ask about PEP immediately.
- Get a baseline HIV test, then follow repeat testing based on clinician guidance.
- Discuss PrEP if you have ongoing or repeated risk.
- Use condoms/barriers and avoid sharing injection equipment.
Testing windows (general guide)
Different HIV tests detect infection at different times after exposure. Exact timing depends on test type and your clinician’s advice.
- NAT (RNA): often detects earlier, roughly 10–33 days.
- Lab antigen/antibody test: commonly 18–45 days.
- Rapid/self antibody-focused tests: may take longer, up to 90 days.
Important limitations
No online calculator can capture every medical detail. Local prevalence, medication adherence, timing, and biological variation all matter. If you are anxious about an exposure, treat this estimate as a starting point and contact a healthcare professional.
You deserve non-judgmental care. HIV prevention and testing are routine healthcare, and early treatment works extremely well.