V belt dimensions by section
Classical sections A through D are the older profile and still the most common on farm and general machinery. Narrow sections 3V, 5V and 8V carry more power in less space and are the usual choice on newer industrial drives. Metric SPZ to SPC are the European equivalents of the narrow range.
Measure across the top of the belt, not the bottom. A worn belt sits lower in the groove but its top width is unchanged.
| Section | Top width (in) | Top width (mm) | Height (in) | Height (mm) |
|---|---|---|---|---|
| Z | 3/8 | 10 | 1/4 | 6 |
| A | 1/2 | 13 | 5/16 | 8 |
| B | 21/32 | 17 | 13/32 | 11 |
| C | 7/8 | 22 | 17/32 | 14 |
| D | 1 1/4 | 32 | 3/4 | 19 |
| 3V | 3/8 | 9.5 | 5/16 | 8 |
| 5V | 5/8 | 16 | 17/32 | 13.5 |
| 8V | 1 | 25 | 7/8 | 23 |
| SPZ | 3/8 | 9.7 | 5/16 | 8 |
| SPA | 1/2 | 12.7 | 13/32 | 10 |
| SPB | 5/8 | 16.3 | 1/2 | 13 |
| SPC | 7/8 | 22 | 45/64 | 18 |
V belt sizes and length numbering
On classical belts the number after the letter is the inside length in inches. Effective or outside length is longer than inside length by a fixed amount that depends on the section, which is where cross-reference confusion usually starts.
Narrow section belts number differently: a 5V750 is a 5V belt with a 75.0 inch effective length. The last digit is a tenth of an inch, not part of a whole number.
| Section | Inside to effective (in) |
|---|---|
| A | +2.0 |
| B | +3.0 |
| C | +4.0 |
| D | +5.0 |
V belt cross reference
Cross-referencing works because the sections are standardised. An A42 from one maker interchanges with an A42 from another, and the common 4L equivalents map directly: 4L is the fractional horsepower equivalent of A, and 5L maps to B.
The trap is length basis. A 4L460 is 46 inches outside length while an A44 is 44 inches inside length, and those are the same belt. If a replacement runs slack or will not go on, check whether the two numbers are quoting the same basis before assuming the part is wrong.
How to measure a V belt
For a belt that is still intact, wrap a string round the inside face, mark the overlap and measure the string. For one that has snapped, lay it flat and measure the inside face end to end.
Then measure the top width and height with a caliper and match it to the section table above. Two numbers, section and length, are all you need to order.
