Odometer Error Calculator
See how far off the odometer reads after a size change. Use the calculator below. Results update as you type.
How the Odometer Error Calculator Works
This calculator works by applying the tire diameter change to a recorded distance to find the miles the odometer misses or over-counts. Larger tires make the odometer under-record.
- Enter the original size and new size, or the diameter change in percent, for example +3%.
- Enter a distance, for example 10,000 miles (16,093 km).
- Read the true distance: 10,300 miles.
- Read the error: the odometer missed 300 miles (483 km).
The Formula
The formula is True Distance = Recorded Distance × (New Diameter ÷ Old Diameter).
True Distance = Recorded × (D_new ÷ D_old) Error = True Distance − Recorded Error (%) = (D_new − D_old) ÷ D_old × 100Worked example: a −2% change (smaller tires) over 50,000 recorded miles gives 49,000 true miles. The odometer over-counted by 1,000 miles (1,609 km).
Conversion Table
The conversion table shows the miles missed or over-counted at 10 diameter changes over 1,000, 10,000, 50,000 and 100,000 miles. A +3% change misses 3,000 miles per 100,000.
Negative values mean the odometer missed distance. Positive values mean it over-counted distance.
| Diameter Change | Per 1,000 mi | Per 10,000 mi | Per 50,000 mi | Per 100,000 mi |
|---|---|---|---|---|
| -4% | +40 | +400 | +2,000 | +4,000 |
| -3% | +30 | +300 | +1,500 | +3,000 |
| -2% | +20 | +200 | +1,000 | +2,000 |
| -1% | +10 | +100 | +500 | +1,000 |
| +1% | -10 | -100 | -500 | -1,000 |
| +2% | -20 | -200 | -1,000 | -2,000 |
| +3% | -30 | -300 | -1,500 | -3,000 |
| +4% | -40 | -400 | -2,000 | -4,000 |
| +5% | -50 | -500 | -2,500 | -5,000 |
| +7% | -70 | -700 | -3,500 | -7,000 |
A larger tire (positive change) travels farther per revolution, so the odometer under-records distance.
What Is the Odometer Error Calculator?
The Odometer Error Calculator is a tool that measures how much a tire size change distorts recorded mileage. The odometer uses the same wheel-turn count as the speedometer, so it carries the same percentage error.
Odometer error affects service intervals, warranty mileage, lease mileage and resale value. A truck with tires 5% larger records 95,238 miles when it has traveled 100,000 miles.
Common Uses
This calculator has 4 uses: service intervals, lease mileage, warranty claims and resale records.
- Plan service intervals: Change oil on true miles.
- Track lease mileage: Know real distance against the lease limit.
- Document warranty claims: Explain mileage differences.
- Keep resale records: Show buyers the true distance.