How To Read V-Belt Numbers

Automotive belts start with either 4L (12.5mm wide) or 3L (9.5mm). The number following it is the outside length of the belt in tenths of inches. The inside length of the belt is typically 2" less for a 4L belt, and 1-1/2" less for a 3L belt. An example would be 4L460, which would be 46" long outside, 44" inside.

"Classic" v-belt numbers start with a letter identifying the cross section, “A” through “E” - see V-Belt Dimensions below.

“A” series belts are the most common. The number following it is the inside length in inches. The outside length is typically 2 inches more. An example would be A44, 44" long on the inside, 46" outside; the equivalent of the 4L460 above.

“4L” belts measure the outside of the belt.

“A” belts measure the inside of the belt. (add 2" to come up with the equivalent 4L size.)

Outside Circumference per section:

  • A = Add 2" to belt number (Example A88 = 90" Outside Circumference)
  • B = Add 3" to belt number (Example B88 = 91" Outside Circumference)
  • C = Add 4" to belt number (Example C88 = 92" Outside Circumference)
  • D = Add 5" to belt number (Example D105 = 110" Outside Circumference)
  • E = Add 6" to belt number (Example E144 = 150" Outside Circumference)
  • AX = Add 2" to belt number (Example AX60 = 62" Outside Circumference)
  • BX = Add 3" to belt number (Example BX50 = 53" Outside Circumference)

Widths:

  • A Section = 1/2" Wide
  • B Section = 5/8" Wide
  • C Section = 7/8" Wide
  • D Section = 1-1/4" Wide
  • E Section = 1-1/2" Wide
  • AX Section = 1/2" Wide
  • BX Section = 5/8" Wide
Section Topwidth, a (Inches) Height, b (Inches) Angle, O Belt Range Inches  
3L 3/8" 7/32" 40 170-1350
4L 1/2" 5/16" 40 170-4000
5L 5/8" 13/32" 40 230-2680
A 1/2" 5/16" 40 15-400
B 5/8" 13/32" 40 20-800
C 7/8" 17/32" 40 32-800
D 1-1/4" 3/4" 40 80-800
E 1-1/2" 29/32" 40 105-800