Your age
How this tool decides
The tool does not calculate anything. It maps your age to a decade and returns that decade's screening ledger, which is the same ledger printed on the decade hubs. Every row was built from the recommending body's own published statement: the US Preventive Services Task Force for the screenings and the CDC and ACIP adult immunization schedule for the vaccines. Each row names that body, prints its letter grade where one exists, and links the source with the source's own date, so a reader can check any line against the document that sets it.
A row that has no dated primary source is not on the ledger. Where a recommendation the site has not yet verified exists, the decade hub says so rather than printing it, because a screening list a reader takes to a clinician has to be right about its sources before it is complete.
How to read a row
Three things on each row decide what it means for you. The population is the group the recommendation was written for, as the source states it; a row for adults 50 to 75 says nothing about a 45-year-old, and a personal or family history can move a start age earlier than the population row shows. The grade is the USPSTF's judgment of how certain and how large the net benefit is (see its grade definitions): A and B recommend the service, C recommends offering it selectively based on professional judgment and patient preference, I means the evidence is insufficient to weigh benefits against harms, and D recommends against it. Vaccine rows carry no letter grade. The frequency is how often, or at what point, the source says to do it.
Take the list to a clinician rather than ordering tests from it. Screening is a decision about probabilities in a population, and a clinician applies it to a person: your history, your prior results and what a positive result would lead to. The preventive-care pillar explains the rows people most often misread, PSA first among them.