How grading works
How card grading actually works
Quick answer: every major grading company scores a card on four independent axes, corners, edges, surface, and centering, then rolls those four numbers into one overall grade. The overall is not an average. It is anchored to the worst axis, because a single ruined corner is still a ruined corner no matter how clean the rest of the card is.
The four sub-grades
Corners
The four corners of the card, checked for whitening, fraying, and softness. A corner that has begun to round or show white fiber under the print layer is the single most common reason a card misses a Gem Mint grade.
Edges
The card's outer border along all four sides. Edges take damage differently from corners, chipping, nicking, and printing roughness along a straight run rather than a single point, and are graded independently.
Surface
The front (and back) face of the card between the borders: scratches, print lines, indentations, staining, and the factory-fresh sheen on foil and holo cards. Surface is the most subjective of the four axes because it is read visually rather than measured.
Centering
How evenly the image sits inside the card's border, measured as a left/right and top/bottom ratio. Centering is the one sub-grade that is fully measurable rather than a judgment call, and it is usually the hardest ceiling to clear for a true Gem Mint or Pristine grade.
How the overall grade is calculated
This is how ZeroPop computes the overall grade from the four sub-grades, and it follows the same BGS-style floor logic the physical grading companies use rather than a simple average:
- Sort the four sub-grades from lowest to highest. The lowest anchors the overall grade.
- If two or more sub-grades tie for lowest, the overall equals that lowest score. No bump.
- Otherwise the overall can rise above the lowest by a bump, capped at the second-lowest sub-grade. The bump is a full point when every sub-grade but one is a 10, and a flat half point otherwise. It is not a gap-scaled bump, it is either +0.5 or +1.0, whichever the card qualifies for, and it can never push the overall past the second-lowest score.
- A near-perfect card can shortcut straight to a 10: all four sub-grades at 9.5 or higher with at least two 10s, or three of the four sub-grades at 10 with the fourth at 9.5 or higher.
- The overall is hard-capped at the lowest sub-grade plus 2.0, then rounded to the nearest half point.
Worked example: corners 9.5, edges 9.5, surface 10, centering 9.0. The lowest is centering at 9.0, and it is the only sub-grade below 9.5, so it does not tie with anything. The bump is a flat half point (not every other axis is a 10), capped at the second-lowest score of 9.5. Overall: 9.5.
The one invariant that never breaks: the overall grade is never lower than the worst sub-grade. A card's weakest axis is always its floor, whichever company grades it.
PSA vs BGS vs CGC
The three major grading companies score the same four axes but present the result differently, and the market treats their numbers differently too.
| Company | Publishes sub-grades | Top grade | Known for |
|---|---|---|---|
| PSA | No, overall only | PSA 10 Gem Mint | Highest resale recognition, largest population database |
| BGS | Yes, all four | BGS 10 Black Label | Sub-grade transparency, premium on modern chase cards |
| CGC | Yes, all four | CGC 10 Pristine | Faster turnaround, growing modern and vintage market |
None of the three is universally “better,” the right company depends on the card and the market you plan to sell into. See the full PSA vs BGS vs CGC vs SGC comparison for cost, speed, and resale data by company.
When to grade a card vs sell it raw
Grading only pays off when the expected value of a graded sale clears the raw price plus submission fees and shipping by a real margin. The two numbers that move that math the most are the gap between a card's raw and PSA 10 price, and your realistic odds of landing that 10. A card that predicts an 8 with a small PSA 10 premium almost never clears the bar; a card that predicts a 9.5 or better with a wide PSA 10 premium usually does.
Run the exact numbers in the slab-or-sell ROI calculator before you submit anything, or read the full decision framework.
Frequently asked questions
What are the four card grading sub-grades?+
Corners, edges, surface, and centering. Each is scored independently on a 1 to 10 scale, then combined into a single overall grade. Corners and edges look for physical wear, surface looks for scratches and staining, and centering is a measured ratio of how the image sits inside the card's border.
How is the overall grade calculated from the sub-grades?+
The lowest of the four sub-grades sets the ceiling. If two or more sub-grades tie for lowest, the overall grade equals that lowest score with no bump. Otherwise the overall can rise above the lowest by half a point, capped at whichever sub-grade is second-lowest, so a single weak axis can only be offset so far by the other three. The full math is below.
Can the overall grade ever beat all four sub-grades?+
No. The overall grade can never fall below the worst sub-grade, and in practice it almost never exceeds the second-lowest sub-grade either. A card with one damaged corner and three perfect axes still grades close to that corner's score, not an average of the four.
What is a Gem Mint 10?+
A card graded 10 (or BGS's Pristine 10 / Black Label) shows essentially no flaws on any of the four axes: sharp corners, clean edges, a flawless surface, and centering inside the tightest published tolerance. The bar rises fast in the top half point, which is why most graded cards land between 8 and 9.5 rather than at a true 10.
What is the difference between PSA, BGS, and CGC?+
PSA publishes a single overall number and is the most recognized name for resale value. BGS publishes all four sub-grades alongside the overall (a BGS 9.5 with four 9.5 sub-grades is a Gem Mint; a rare BGS 10 across all four is a Black Label). CGC is the newer entrant with faster turnaround and a growing secondary market. See the full comparison below.
Should I grade a card or sell it raw?+
Grade it when the expected value of a graded sale, weighted by your realistic odds at each grade, clears the raw price plus the grading fee and shipping by a comfortable margin. A card with a small gap between its raw and PSA 10 price rarely clears that bar. Run the exact numbers in the ROI calculator before you submit anything.
Grading costs and turnaround
What grading actually costs and how long it takes varies a lot by company and tier. These guides break down real current pricing and wait times.
PSA grading cost, every tier
What PSA charges from Value to Premium, $25 to $10K, with real turnaround by tier.
Cheapest ways to grade a card
SGC bulk, group submissions, and CGC value tier, the actual cheapest paths under $10 a card.
Grading turnaround times
Current wait times for PSA, BGS, CGC, and SGC, plus the seasonal patterns that move them.
Best card grading apps
ZeroPop and every other AI card scanner ranked on accuracy, sub-grades, and ROI tools.
When to cross PSA, BGS, CGC
Crossover submissions explained, and how to predict the new grade before you pay the crossover fee.
See real graded population data.
Browse community sub-grade averages and current market prices for thousands of cards, sourced from real ZeroPop scans, in Explore.
Related reading: The complete guide to card grading, BGS sub-grades explained, what every grade looks like on real scans, and the ZeroPop population report.