BGS and CSG Sub-Grades Explained: Centering, Corners, Edges, Surface
What sub-grades actually mean, how they roll up to an overall grade, and which sub-grade carries the most weight in determining final BGS or CSG grade.
PSA gives you one number. BGS, CSG, and (on report) some others give you four. Sub-grades are the breakdown of how a grader scored each individual aspect of the card — and understanding them lets you predict the overall grade like a pro.
The four sub-grades
Every modern grader uses the same four:
- Centering — left/right and top/bottom border ratios.
- Corners — sharpness, whitening, fraying, dings.
- Edges — chipping, paper loss, edge wear.
- Surface — scratches, print lines, gloss damage, indentations.
Each is graded 1 through 10 in half-point increments (BGS uses 1–10 with 0.5 increments).
How sub-grades roll up
The overall BGS grade is not an average. It's closer to a worst-case rule with some allowances:
- All four sub-grades 9.5 or higher → likely overall 9.5 (Gem Mint).
- All four sub-grades 10 → 10 Pristine (Black Label).
- One sub-grade at 9, others at 9.5+ → probably overall 9 (Mint).
- One sub-grade significantly weaker drags the overall grade down to that level.
The lowest sub-grade caps the overall — but only if it's notably lower than the others. A "9.5, 9.5, 9.5, 9" can still grade overall 9.5 because three of four are clean.
Which sub-grade matters most
Two sub-grades drive almost all sub-10 grades:
- Centering — the silent killer. Most modern cards fail at 60/40 fronts or worse on the back.
- Corners — even microscopic whitening drops the corner score, which often caps the overall.
Surface and edges matter, but unless the card has visible damage, those usually score 9.5+.
The PSA flip side
PSA does not put sub-grades on the slab. They will produce them on a separate report (extra fee) but the grade you see is one number. This makes PSA grading harder to reverse-engineer — you only see the final answer.
If you want sub-grades on the label, use BGS or CSG. If you want the strongest market premium, use PSA.
Use sub-grades as a learning tool
Submit a small batch of cards to BGS, get the sub-grades back, and compare them to your AI predictions and your own estimates. This is how you calibrate your eye. After 50 graded cards with sub-grades, your screening accuracy will be dramatically better.
How AI sub-grade predictions work
Modern AI graders predict each sub-grade individually using the same visual evidence a human grader uses:
- Computer vision measures border widths for centering.
- Edge and corner crops are scored for whitening and damage.
- Surface analysis detects print lines and scratches.
CardSense AI returns four predicted sub-grades on every scan, plus the overall grade prediction. Use the breakdown to identify exactly which sub-grade is dragging the card down — and decide if it's worth fixing the photo or accepting the grade.
The bottom line
Sub-grades are the X-ray of card grading. Once you understand them, you stop guessing and start diagnosing. Use them to learn, to crossover-target, and to choose between BGS, PSA, and CSG with intent.
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