How to calculat life of machine belt?

like v belt,flat belt|||Check it every oil change for cracks and to see if it is getting loose.|||by counting on it|||There is no real answer to this it depends on tension and speed. However if you are really interested then go to a belt manufacturer and ask them.What I have learnt from experience is that over a given time a belt is monitored and say 2 months down the track it brakes then the chances are that the same time frame can be expected for the next belt. This particularly applies on the tension placed on belt.|||Depends on the application. If you have a mid 1970's car that uses a V-belt, you can count on about two to three years of use. A Serpentine belt can last up to 100,000 miles, "IF" all the pullyes and idler pulleys are in good shape. If not, the serpentine belt can wear out in minutes.