Commercial Truck Tire Size Tool
Check sizes for big trucks and their loads. Use the calculator below. Results update as you type.
How the Commercial Truck Tire Size Tool Works
This tool works by decoding commercial truck sizes, including half-inch rims such as 19.5 in, 22.5 in and 24.5 in, into diameter and revolutions. It flags the gap between nominal values and the maker's published revs per mile.
- Enter the size, for example 295/75R22.5.
- Read the nominal diameter: 39.9 in (1,014 mm).
- Read the nominal revs per mile (505) and revs per km (314).
- Enter the maker's published revs per mile for exact fleet calibration.
The Formula
The formula is the standard diameter formula with fractional rim sizes.
D (mm) = (Rim × 25.4) + 2 × (Width × Aspect Ratio ÷ 100) Revs per Mile = 1,609,344 ÷ (π × D (mm)) Revs per km = 1,000,000 ÷ (π × D (mm))Worked example: 315/80R22.5 has a 252 mm sidewall, a 571.5 + 504 = 1,075.5 mm (42.3 in) diameter and 476 revs per mile.
Conversion Table
The conversion table lists nominal dimensions for 10 commercial sizes from 225/70R19.5 to 385/65R22.5. Diameters run from 31.9 in (810 mm) to 42.3 in (1,076 mm).
The note under the table reminds fleets to use published revs per mile. Truck tire makers list that figure for every size and tread pattern.
| Size | Diameter (in) | Diameter (mm) | Revs / Mile | Revs / km |
|---|---|---|---|---|
| 225/70R19.5 | 31.9 | 810 | 632 | 393 |
| 245/70R19.5 | 33.0 | 838 | 611 | 380 |
| 255/70R22.5 | 36.6 | 928 | 552 | 343 |
| 275/70R22.5 | 37.7 | 956 | 536 | 333 |
| 275/80R22.5 | 39.8 | 1,012 | 506 | 315 |
| 295/75R22.5 | 39.9 | 1,014 | 505 | 314 |
| 295/80R22.5 | 41.1 | 1,044 | 491 | 305 |
| 315/80R22.5 | 42.3 | 1,076 | 476 | 296 |
| 285/75R24.5 | 41.3 | 1,050 | 488 | 303 |
| 385/65R22.5 | 42.2 | 1,072 | 478 | 297 |
Commercial tires are bought on published revs/mile; nominal values differ from published values by 1–3%.
What Is the Commercial Truck Tire Size Tool?
The Commercial Truck Tire Size Tool is a tool that decodes medium- and heavy-duty truck tire sizes and their published dimensions. Commercial tires mount on tubeless rims in half-inch sizes that do not fit passenger or light truck wheels.
Fleets buy tires by revolutions per mile. That number sets the tachograph, the engine control module (ECM) speed calibration and fuel-mileage reporting.
Common Uses
This tool has 4 uses: fleet calibration, steer and drive matching, ECM setup and size substitution.
- Calibrate fleets: Set tachographs and telematics.
- Match steer and drive tires: Compare positions.
- Program the ECM: Enter revs per mile after a size change.
- Substitute sizes: Compare low-profile and standard sizes.