Stamp grading combines several factors — centering, margins, gum, perforations, and cancels — into a single grade from Poor to Superb. This reference explains each grade and includes a centering-ratio calculator that turns your measured margins into a centering grade.
The five standard grade bands
Philatelic grading uses five descriptive tiers, and most major grading services (PSE, PF, and others) also assign a numeric score from 10 to 100 that maps onto these bands:
| Grade | Common abbreviation | Centering balance (approx.) |
|---|---|---|
| Superb | S | 48 to 50 — nearly perfect |
| Extremely Fine | XF | 40 to 47 — noticeably even margins |
| Very Fine | VF | 30 to 39 — off-center but design clear |
| Fine | F | 20 to 29 — clearly off-center, perfs clear |
| Average or below | Avg / Poor | Under 20 — design may touch perfs |
How centering is measured
Centering is judged by comparing opposite margins. On each axis, take the narrower margin as a share of the total of the two opposite margins:
horizontal balance = min(left,right) / (left + right) × 100
vertical balance = min(top,bottom) / (top + bottom) × 100
centering grade = driven by the worse of the two balancesA balance near 50% is perfectly centered. The overall centering grade follows whichever axis is weaker, so a stamp perfectly centered left-to-right but badly off vertically is still graded on the vertical shortfall.
Worked example
A stamp with left/right margins of 1.0 mm and 1.4 mm has a horizontal balance of
1.0 / 2.4 ≈ 42%, which sits in the Extremely Fine band. If its vertical margins
were 0.6 mm and 1.4 mm, the vertical balance is 0.6 / 2.0 = 30%, only Very Fine,
and the overall centering grade follows the worse axis — so this stamp is VF on
centering despite its excellent horizontal balance.
Beyond centering: gum and perforations
Centering is the single biggest driver of grade and price, but it is not the only factor:
- Gum condition (unused stamps): Original gum never hinged (OG NH or MNH) commands the highest premium. A light hinge remnant (LH) reduces value. Regummed stamps — where a dealer re-applies gum to simulate MNH — are a known fraud and dramatically lower the certified grade.
- Perforations: All perfs must be intact, intact, and evenly distributed. Short or missing perfs lower any grade to Fine or below regardless of centering. Pulled perfs can be hidden under a hinge or photo angle, so check carefully.
- Cancels (used stamps): A light, readable cancel that leaves the design fully visible is preferred. A socked-on-the-nose (SOTN) circular date stamp placed neatly over the stamp’s corner can actually add collector interest. Heavy smudged cancels or pen cancels lower a used stamp’s grade.
Practical advice for collectors
When grading your own stamps, measure the margins with a millimeter rule and use the centering calculator before forming a price expectation. A stamp that feels “about right” visually often turns out to be VF rather than XF when measured — and the difference between VF and XF on a classic definitive can be substantial. Major grading societies issue tamper-evident certificates for valuable stamps; third-party certification is standard practice for any stamp above a threshold you are comfortable with.