How Centering Is Measured
Measure the border on each side of the card in millimetres. Compare left with right and top with bottom. The ratio is the larger border's share of the pair: borders of 2 mm and 3 mm make 60/40, whichever side is wider.
Each face is judged by its worse axis. A card perfectly centered side to side but 70/30 top to bottom is a 70/30 card.
How Centering Limits a PSA Grade
PSA publishes a centering tolerance for each grade, and it works as a ceiling. No amount of sharp corners or clean surface lifts a card past the grade its centering allows. The front and back each have their own tolerances, the back far looser, and the worse of the two wins.
A card within a point of a tolerance line is a judgement call. Graders read visual centering, not a ruler, so a borderline card often comes back a grade lower than the math says.
Measuring Tips
Use a centering tool or a ruler marked in half millimetres, or measure a straight, square photo. Measure to the inner print frame, not to any artwork that bleeds past it, and measure the back as carefully as the front.
Frequently Asked Questions
What centering does a PSA 10 need?
PSA sets a front and a back tolerance for each grade. The calculator above lists every published tolerance and checks your measurements against them.
How do I calculate centering on a trading card?
Measure opposite borders, divide the larger by their sum and multiply by 100. Borders of 2 mm and 3 mm give 3 divided by 5, or 60/40.
Does the back of the card matter for centering?
Yes, but its tolerances are much looser than the front's. The worse of the two faces sets the ceiling.
Can a perfectly centered card still miss a 10?
Yes. Centering only sets a ceiling. Corners, edges, surface and print quality each set their own, and the lowest one is the grade.