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Belt Tension Calculator

(Calculates the force exerted by an endless belt on a pulley, i.e., the force of two belt strands)
We recommend stretching most unreinforced belts at least 5%. The calculated tensions are less accurate above 25% stretch. Usually 83A/85A durometer belts are stretched 10-12%, and 92A/95A durometer belts are stretched 7-9%. Do not use this calculator to estimate tension for reinforced belts.

Force to stretch a Urethane Round Belt
Select a Durometer:  
Stretch %  (enter 10 for 10%)
Cross section diameter (inches)
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Belt Tension (lbs)
After 1 week the tension drops to (lbs)
and remains relatively constant thereafter*.

Convert units to:    
Force to stretch a Urethane Flat Belt:
Select a Durometer:  
Stretch %  (enter 10 for 10%)
Thickness (inches)
Width (inches)
    Help
Belt Tension (lbs)
After 1 week the tension drops to (lbs)
and remains relatively constant thereafter*.

Enter one:

  
Enter one:

  
Target Tension for a Urethane Flat Belt:
Select a Durometer:  
Initial Belt Tension (lbs)   For belts wider than 4" (100mm), use 80 lbs (356 N)
Thickness (inches)
Width (inches)   Enter the total width of
all belts on the drive roller.
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Belt Stretch %
For wide flat belts, use 80 lbs (356 N) for belt tension.

Bearing Load: Standard 1.9" (50mm) diameter conveyor rollers are normally rated at 250 lbs (110 kg) maximum load. The plastic fixture that holds the bearing is the limiting factor. For idler pulleys the maximum load is determined by the bearing itself. Our idler pulleys use the 6203 bearing, rated at 600 lbs (270 kg) at typical conveyor speeds. Make sure that your belt tension does not exceed the rating of your application. If you use multiple belts per roller consider the total bearing load when calculating the % stretch to use.

*Tension vs. Time: Urethane belt tension declines dramatically after installation. In the first 5 minutes it typically declines by 30%. After about a week of run-in the tension plateaus and remains relatively constant thereafter, declining very slowly at a diminishing rate over time. The chart below shows an example of this. Incidentally, dynamic tension always measures below static tension, so if this test were done without rotating the rollers, the plateaued tension would be about two pounds higher.

Tension vs. Time graph

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