Automotive Calculators
Speedometer Error Calculator
Find out how much your new tire size shifts your speedometer reading and odometer accuracy. Enter stock and new tire sizes to calculate the error.
FreeActual SpeedOdometer ErrorNo sign-up
Tire Sizes
Stock (Original) Tire
New (Replacement) Tire
Indicated Speed
mph
Actual Speed
59.0
mph when speedo shows 60 mph
Speed Error
-1.7%
slower than shown
Odometer Error
-1.7%
per year of driving
Error between 1.5–3% — within tolerable range but worth noting.
How Speedometer Error Is Calculated
Speedometer error = (New Tire Diameter / Original Tire Diameter − 1) × 100%. A larger tire makes your speedometer read low (you're going faster than shown). A smaller tire makes it read high (you're going slower than shown).
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