PSA grades four things: centering, corners, edges and surface. The last three need a loupe, good light and a trained eye. Centering does not: it can be measured. And it is the most common reason a card that looks perfect comes back a 9 instead of a 10.
The tolerances PSA requires
Centering is the split of the border between two opposite sides. 55/45 means the wider border takes 55 % and the narrower one 45 %. PSA sets a limit for each grade, and the front is much stricter than the back:
- PSA 10 (Gem Mint): up to 55/45 on the front and 75/25 on the back.
- PSA 9 (Mint): up to 60/40 on the front and 90/10 on the back.
- PSA 8 (NM-MT): up to 65/35 on the front.
- PSA 7 (NM): up to 70/30 on the front.
- PSA 6 (EX-MT) and PSA 5 (EX): up to 80/20 and 85/15 on the front.
The limit applies to each axis separately: left/right and top/bottom. The worse of the two decides.
How to measure it from a photo
- Take the card out of its sleeve or toploader and lay it on a plain background that contrasts with its border.
- Shoot straight on, without tilting the phone and without glare, leaving background around all four sides.
- Measure the border width on each side and work out the split: left border divided by left plus right.
- Repeat for top and bottom, then for the back.
Doing it by hand with a ruler works, but it is slow and easy to get wrong by a millimetre. The TCGJoin card grading calculator does it from a photo: it finds the card, measures all four borders in your browser (the photo never leaves your device) and tells you the highest grade that centering allows. If the measurement is unreliable it warns you, and you can adjust the lines by hand.
Does grading pay off?
Good centering is not enough: you need to run the numbers. Take the graded price and subtract the raw price, the grading fee and insured shipping. If the margin only works with a 10 and your centering barely reaches 55/45, the risk of landing a 9 is real and can turn a profit into a loss.
The calculator does that sum for you: enter the raw price, the graded price and the cost, and it tells you whether you make money and how much cushion you have. If the card is in your collection, it pulls in the price for you.