Principia College operates as a private nonprofit institution located in Elsah, Illinois (rural: fringe), with a total reported enrollment of 339 students of which 378 are undergraduates. Institution-level records in the Integrated Postsecondary Education Data System (IPEDS) classify each school by Carnegie category, ownership sector, and urban/rural locale, which is how this profile's peer group and cost cohort are determined; Principia College is categorized as "Baccalaureate Colleges: Arts & Sciences Focus" under the Carnegie classification system, a meaningful signal when comparing like-to-like institutions.

Admissions and cost figures below come from the same annual IPEDS Fall enrollment survey and net-price calculation that every Title IV institution is legally required to submit to the federal government, so the same standardized methodology applies whether comparing a public flagship or a small private college. Net price nets grant and scholarship aid out of the published sticker price, the number financial-aid experts consider the honest comparison point - the table further down breaks that figure out by family income band rather than a single blended average, since what one family actually pays can look very different from what another family pays at the identical school.

The outcomes further down come from federal tax records the U.S. Treasury links to former students who received federal financial aid, not a self-reported alumni survey - an approach that removes response bias but also means graduates who never took federal aid are absent from the earnings figures. Completion and retention rates only count first-time, full-time degree-seeking students, so a school with a large transfer or part-time population can serve those students well without that showing up in these particular metrics. Reading the cost, completion, and earnings figures together, rather than any single one in isolation, is the approach the College Scorecard's own methodology recommends for judging return on investment.