If you cannot determine the number of waste tires present using a direct count alone, the resources on this page will help you to determine the approximate number of tires at a site using volumetric estimation. Numbers of whole waste tires are estimated by volume (in cubic yards). Numbers of altered tires (in passenger tire equivalents) can be estimated by volume or by weight. When using waste tire volumes or weight to estimate the number of waste tires present, inspectors must deduct 20% from every estimate to yield a conservative estimate with an adequate margin of error. Before determining the number of waste tires, make sure you understand the definitions of waste and other tires. For inspection purposes, only waste tires are counted toward total number of tires allowed.

Estimating Volumes of Tire Piles

Use the Waste Tire Math Reference to estimate volumes of various shapes of waste tire piles you encounter in the fold. Depending on the waste tire pile configurations you find, you may need to:

  • Break up the pile(s) into separate volume shapes.
  • Calculate the volume for each volume shape using the appropriate formula based on their shape.
  • Combine the individual volumes for the total pile volume estimate.

Converting Cubic Feet to Cubic Yards

Once you have calculated the volume of the tire pile(s) in cubic feet, you need to convert the volume to cubic yards as follows:

Volume (in cubic feet) ÷ 27 = Volume (in cubic yards)

Converting Cubic Yards to Number of Tires

Once you have determined the volume of the waste tire pile(s) in cubic yards, multiply the cubic yards by the appropriate conversion factor as listed in the tables below for whole or altered tires. To use this table you will need to know the height of the tire pile, how the waste tires are stored, and approximately how long the waste tires have been stored.

Whole Passenger/Light Truck Tires
Storage TypeHeight of Tire Pile
(Stored less than 15 years)(<10 feet)(10-15 feet)(>15 feet)
Loose10 tires/cy12 tires/cy14 tires/cy
Barrel12 tires/cy14 tires/cy16 tires/cy
Laced14 tires/cy16 tires/cy18 tires/cy
(Stored 15 years or more)
Loose12 tires/cy14 tires/cy16 tires/cy
Barrel14 tires/cy16 tires/cy18 tires/cy
Laced16 tires/cy18 tires/cy20 tires/cy
Whole Semi-Truck Tires
Storage TypeHeight of Tire Pile
(Stored less than 15 years)(<10 feet)(10-15 feet)(>15 feet)
Loose2.5 tires/cy2.75 tires/cy3.0 tires/cy
Barrel4.2 tires/cy4.4 tires/cy4.6 tires/cy
Laced4.1 tires/cy4.3 tires/cy4.5 tires/cy
(Stored 15 years or more)
Loose3.0 tires/cy3.5 tires/cy4.0 tires/cy
Barrel4.4 tires/cy4.6 tires/cy4.8 tires/cy
Laced4.3 tires/cy4.5 tires/cy4.7 tires/cy
Altered Tires
Sidewalls or treads20  tires/cyThe photo below shows cut out sidewalls and treads.
Primary shreds20 tires/cyTires that have been run through a shredder one time.
Shreds 2 inches or smaller40 tires/cyTires that have been run through a shredder more than once to create pieces two inches or smaller.
Crumb rubber (less than ¼ inch in size) NANot regulated by the California Department of Resources Recycling and Recovery.

Cut tires: sidewalls and treadsConverting Pounds to Passenger Tire Equivalents (PTE)

If you know the weight of altered tires, you can convert directly to a number of passenger tire equivalents (PTE).

The California Code of Regulations, 14 CCR Section 17225.770 defines a "passenger tire equivalent" (PTE) as the total weight of altered waste tires, in pounds, divided by 20 pounds. 1 PTE = 1 Waste Tire. Total Known Weight (pounds) ÷ 20 pounds = PTE.

Passenger Tire Equivalents Guide

20 lbs = 1 PTE
1 whole tire = 2 sidewalls and 1 tread (regardless of tire size)
1 tread = 2 sidewalls (regardless of tire size)
1 sidewall = 25% of the weight of a tire (regardless of tire size)
4 passenger tire sidewalls = 1 PTE
1 tread = 50% of the weight of a tire (regardless of tire size)
Semi-truck tires weigh 80-120 lbs. Calculate 1 semi-truck tire as 4 PTE
2 semi-truck tire sidewalls = 2 PTE
1 semi-truck tread = 2 PTE
1 motorcycle tire = 1 PTE
1 bale = 60 to 80 tires (ask the operator)