Horsepower rating formulas

XL (0.38) width
HP = K_z [ d ( r / 1000 ) ( 0.0916 - 7.07 x 10^-5 (d r)² ) ]

L (1.00) width
HP = K_z [ d ( r / 1000 ) ( 0.436 - 3.01 x 10^-4 (d r)² ) ]

H (3.00) width
HP = K_z [ d ( r / 1000 ) ( 3.73 - 1.41 x 10^-3 (d r)² ) ]

XH (4.00) width
HP = K_z [ d ( r / 1000 ) ( 7.21 - 4.68 x 10^-3 (d r)² ) ]

XXH (5.00) width
HP = K_z [ d ( r / 1000 ) ( 11.4 - 7.81 x 10^-3 (d r)² ) ]

Where:

HP = the maximum horsepower rating recommended for the specified standard belt width having six or more teeth in mesh and a pulley surface speed of 6500 fpm or less.
d = pitch diameter of smaller pulley in belt mechanism, inch.
r = rpm of fastest shaft
K_z = HP rating multiplier (see Table Below). Torque ratings for drives with less than six teeth in mesh must be corrected as shown.

Horsepower ratings for drives with less than six teeth in mesh must be corrected as shown in Table given below

FPM to RPM Equation:

r = s / ( π d )

RPM to FPM Equation:

s = r π d

Where:

r = rpm
s = ft / min
d = diameter of pulley in ft

Note:

• Total horsepower ratings are the same for double-sided as for single-sided belts.
• Manufacturers specify percentage of horsepower available for each side of the belt.