Tire size calculator
Compare two tire sizes side by side: overall diameter, width, sidewall height, circumference and revolutions per mile, plus how your speedometer reading changes. Type sizes in any common format.
275/65R20 compared with LT275/65R20
The new size (LT275/65R20) has the same overall diameter as the current size (275/65R20) to two decimal places.
| Measurement | Current (275/65R20) | New (LT275/65R20) | Difference (new minus current) |
|---|---|---|---|
| Overall diameter | 34.1 in (866 mm) | 34.1 in (866 mm) | 0.0 in (0 mm), 0.00% |
| Section width | 10.8 in (275 mm) | 10.8 in (275 mm) | 0.0 in (0 mm) |
| Sidewall height | 7.0 in (179 mm) | 7.0 in (179 mm) | 0.0 in (0 mm) |
| Circumference | 107.0 in (2719 mm) | 107.0 in (2719 mm) | 0.0 in (0 mm) |
| Revolutions per mile | 592 | 592 | 0 |
These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.
Is the difference small?
The overall diameter differs by 0.00%, which is within the common 3% rule of thumb.
The rule of thumb keeps a replacement size within about 3% of the original overall diameter. It covers diameter only. It is not a fit, load or safety check, because width, wheel diameter, load capacity and clearance matter too. Confirm any size change with your vehicle's owner's manual or a tire professional.
Speedometer difference
The two sizes have the same overall diameter to two decimal places, so the speedometer reading would not change in any way you could see.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.0 mph | 0.0 mph |
| 30 mph | 30.0 mph | 0.0 mph |
| 40 mph | 40.0 mph | 0.0 mph |
| 50 mph | 50.0 mph | 0.0 mph |
| 60 mph | 60.0 mph | 0.0 mph |
| 70 mph | 70.0 mph | 0.0 mph |
| 80 mph | 80.0 mph | 0.0 mph |