| Size 1 | Size 2 | Diff | Diff(%) | |
|---|---|---|---|---|
| Diameter | 25.0" | 25.4" | 0.5" | 1.89% |
| Width | 7.7" | 8.5" | 0.8" | 10.26% |
| Circumference | 78.4" | 79.9" | 1.5" | 1.86% |
| Profile height | 5.0" | 4.2" | -0.7" | -15.08% |
| Turnover per mile | 807 | 793 | 14 | -1.73% |
| Clearance | - | - | +0.2" | - |
Speedometer Error
(First wheel OEM size)
| Reading | 20 mph | 30 mph | 40 mph | 50 mph | 60 mph | 70 mph | 80 mph | 90 mph |
|---|---|---|---|---|---|---|---|---|
| Actual | 20.4 | 30.5 | 40.7 | 50.9 | 61.1 | 71.2 | 81.4 | 91.6 |
Tire Size Upgrade Calculator
TireCalc is a free tire size upgrade calculator for quick old-vs-new comparison. Enter your current and target tire sizes to instantly see diameter difference, tire circumference change, and visual fitment impact.
Use this as a tire size speedometer calculator before upsizing or downsizing. The table and speed block show speedometer error at common speeds, so you can understand how your actual speed changes after a tire swap.
It also works as a practical tyre fitment calculator by showing clearance change and sidewall/rim differences. This helps reduce rubbing risk and avoid uncomfortable combinations.
Looking for which tires fit your exact car? We are preparing a separate vehicle-based page (make/model/year) for that use case. This page focuses on size-to-size comparison and speed/clearance math.