How is a prorated tire price calculated?
A $160 tire worn from 10/32" to 6/32" has used 50%of its usable tread (2/32" is the limit), so the prorated value is $80 and you pay $80. On a 60,000 mile warranty, a tire that wears out at 35,000 miles has 58.3% of the mileage used: you pay $93.33 and the credit is $66.67.
New all-season tires often start around 10/32" (≈ 8 mm); winter and truck tires may be deeper.
Measure at the lowest point across the tread for safety and warranty decisions.
Many regions use 2/32" as the legal minimum; tread at or below this is treated as worn out.
Use your original purchase price or the current replacement price, depending on how your warranty or insurer calculates credit.
Usable Tread Remaining
50.0%
Based on usable tread above the minimum (2/32"), matching many tread-based warranty and protection formulas.
Original
10/32"
Current
6/32"
Usable Remaining
4.0/32"
Prorated Value
$80.00
There is usable tread above the minimum, so a tread-based credit applies. Check your own warranty for its exact terms.
Get a plain-English explanation of your results and what they mean for your vehicle.
Tire Pro Rata Chart: Prorated Value by Tread Depth and Mileage
By tread depth
| Tread now | Usable tread left | Prorated value (credit) | Betterment (you pay) |
|---|---|---|---|
| 9/32" | 87.5% | $140.00 | $20.00 |
| 8/32" | 75% | $120.00 | $40.00 |
| 7/32" | 62.5% | $100.00 | $60.00 |
| 6/32" | 50% | $80.00 | $80.00 |
| 5/32" | 37.5% | $60.00 | $100.00 |
| 4/32" | 25% | $40.00 | $120.00 |
| 3/32" | 12.5% | $20.00 | $140.00 |
| 2/32" | 0% | $0.00 | $160.00 |
$160 tire, 10/32" tread when new, 2/32" (1.6 mm) minimum.
By warranty mileage
| Miles received | Share of warranty received | You pay | Credit |
|---|---|---|---|
| 15,000 | 25% | $40.00 | $120.00 |
| 30,000 | 50% | $80.00 | $80.00 |
| 35,000 | 58.3% | $93.33 | $66.67 |
| 45,000 | 75% | $120.00 | $40.00 |
| 60,000 | 100% | $160.00 | $0.00 |
$160 tire, 60,000 mile warranty. Figures are calculated with the formulas on this page.
Tread Depth in 32nds of an Inch and Millimeters
| 32nds of an inch | Millimeters | Note |
|---|---|---|
| 11/32" | 8.7 | |
| 10/32" | 7.9 | |
| 9/32" | 7.1 | |
| 8/32" | 6.4 | |
| 7/32" | 5.6 | |
| 6/32" | 4.8 | |
| 5/32" | 4.0 | |
| 4/32" | 3.2 | |
| 3/32" | 2.4 | |
| 2/32" | 1.6 | Minimum tread in the Continental and Bridgestone warranties quoted below |
| 1/32" | 0.8 |
1/32 inch = 0.79375 mm, rounded to one decimal. These are conversions, not replacement thresholds.
How Tire Makers Calculate a Prorated Price
Continental
Tread: the replacement price is the percentage of usable tread worn multiplied by the dealer's price at the time of the adjustment, excluding taxes. Usable tread is the original tread down to the wear indicators (2/32 inch or 1.6 mm remaining). Mileage: the price is the mileage received divided by the mileage warranted, multiplied by the current price of a comparable tire, rounded to the nearest whole percent. Pro-rata coverage runs up to 72 months from the purchase date, and the mileage warranty needs a completed rotation schedule.
Bridgestone
Tread: the percent of used treadwear multiplied by the dealer's then current selling price. Mileage: the percent of warrantied mileage obtained multiplied by that price. The tire must not be worn to 2/32 inch (1.6 mm) or less, coverage extends up to 5 years from purchase, and taxes, mounting, balancing and disposal fees may be added.
Michelin
Mileage treadwear warranties vary by tire line. The limited warranty for defects runs for the life of the original usable tread or 6 years from purchase, whichever occurs first.
Sources: Continental Total Confidence Plan policy (Canada edition, April 2025), Bridgestone tire warranty manual, Michelin warranty information. Check your own tire line's terms, because they differ.
How to Use This Calculator
- Pick Tread-based or Mileage-based.
- Tread-based: enter the tread depth when new, the tread depth now (measure at the lowest point), and the minimum tread. The minimum is 2/32" (1.6 mm) in the makers' warranties quoted below.
- Mileage-based: enter the warranted mileage and the mileage received. Use the odometer difference between installation and wear-out.
- Enter the price of one tire. Makers use the dealer's current selling price for a comparable tire.
- Read the share of tread or mileage left, the prorated value (credit) and the betterment (the part you pay).
Formulas and Worked Examples
About Tire Proration
Tread-based and mileage-based warranties
A tread-based claim compares the tread left with the tread the tire started with. A mileage-based claim compares the miles received with the miles warranted. Both end in the same step: a share multiplied by the dealer's current price. If you only have a depth gauge reading in 32nds, the tread depth calculator converts it to millimeters.
Age and condition
Warranty time limits count from the purchase date. Where there is no receipt, Continental's policy uses the manufacture date from the DOT code, which the tire date code decoder reads.
Used tires
The tread formula gives a value for a used tire from the new price, but it is not a market price. Before you buy or sell a used set, the checks to make before buying discounted tires cover age, load index and speed rating.