What does centering mean in stamp grading?

Centering describes how evenly the design sits inside the four margins. A perfectly centered stamp has equal left/right and top/bottom margins. Centering is the single biggest factor in a stamp's grade.

How is the centering ratio calculated?

Compare the narrower margin to the wider one on each axis. A ratio of left to right (and top to bottom) of about 50/50 is Superb, 60/40 is XF, 70/30 is VF, and worse than 80/20 falls to Fine or below.

What is the difference between VF and XF?

Very Fine (VF) stamps are well centered with the design clear of the perforations but slightly off true center. Extremely Fine (XF) stamps are very close to perfectly centered with wide, balanced margins. XF commands a strong premium.

Does gum condition affect the grade?

Yes, for unused stamps. Original gum that is never hinged (MNH) is most valuable. Hinged, disturbed, or regummed gum lowers the grade and value. Used stamps are judged on cancel and centering instead.

Why is a light cancel better on a used stamp?

A light, neat cancel leaves the design fully visible and is preferred. A heavy smudged cancel that obscures the design lowers the grade, even on a well-centered stamp. Socked-on-the-nose circular cancels can add value.

Stamp Condition Grade Reference

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.

How it works

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 balances

A balance near 50% is perfectly centered. The grade tiers are roughly: Superb 48-50, XF 40-47, VF 30-39, Fine 20-29, and below 20 is Average or worse.

Example and notes

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. Remember centering is one factor: a perfectly centered stamp with disturbed gum or a heavy cancel still grades down. Major societies such as PSE and PF certify grades on a 70-point numeric scale layered on top of these descriptive tiers.