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.

The following steps make up the Volumetric Calculation Formula:

(Step 1) (Step 2) (Step 3)
(Calculate Tire Volume) x (Select Conversion Factor) x (Apply Deduction) = Final Waste Tire Count

Step 1: Calculate the Volume of Waste Tire Pile in Cubic Yards

Use the Waste Tire Math Reference Guide to estimate the volumes of various shapes of waste tire piles you encounter in the field. 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 separately using the appropriate formula based on their shape.
  • Combine the individual volumes to get the total pile volume estimate.

Measurements of waste tire piles are typically taken in feet, but once you have calculated the volume of the tire pile(s) in cubic feet, you need to convert the volume to cubic yards (cy) as follows:

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

Step 2: Select Pile Type Conversion Factor to Convert to 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)(Less than 10 feet)(10-15 feet)(Greater than 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)(Less than 10 feet)(10-15 feet)(Greater than 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.

Step 3: Apply Deduction

Deduct 20% from Volumetric Estimates, Count Averages, and Questionable Counts (multiply by 0.8). 100%-20%=80% therefore the resulting volume is 80% of the original calculated estimate. 80% is calculated by multiplying 0.8 by the original calculated volume estimate. This deduction would apply to volumetric estimates, count averages, and direct counts of small tire piles where you cannot unquestionably count every tire, but where volumetric estimation would be less accurate. An example of a count average would be finding 19 stacks that appear to each be 8 tires high. If you do not count each tire, but instead calculate 19 x 8 = 152, then apply the deduction (152*0.8= 121) and list the total as 121.

Note: You might find a portion of tires present that you can unquestionably count and another portion that you cannot. In such cases, deduct 20% from only the portion you cannot unquestionably count.

Putting the Equations Together

To calculate the number of tires in a pile, use this formula:

(Step 1) (Step 2) (Step 3)
(Calculate Tire Volume) x (Select Conversion Factor) x (Apply Deduction) = Final Waste Tire Count


Counting Whole Tires

When counting whole tires, each tire counts as one tire regardless of size or mass.

Crumb Rubber

Waste tire material less than or equal to ¼ inch in size (6mm) is not regulated by CalRecycle. (See 14 CCR 17225.720 and 14 CCR 18450(a)(38).

Converting Pounds to Passenger Tire Equivalents (PTE)

Cut tires: sidewalls and treads

If you know the weight of altered tires, you can convert directly to a number of passenger tire equivalents (PTE). PTE is only to be used for volumetric calculations of altered waste tires. Never calculate or incorporate PTE in any whole tire count.

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)