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Units and precision
Display units change presentation; the underlying geometry stays the same.
Reviewed Oct 27, 2026
Choose metric or imperial display
Metric length results use millimeters. Imperial length results use inches. The printed tire marking retains its conventional mixed units: millimeter width, percentage aspect ratio and inch rim diameter. Wheel-width inputs likewise remain explicitly labeled.
Round only the displayed result
TireSpan calculates from the original numeric inputs and retains precision between steps. A displayed diameter or circumference may show fewer digits than the internal value. Switching units and switching back should not change the stored input or the computed geometry.
Understand a displayed zero
A small result can round to zero at the chosen display precision. Exact same-size comparisons are zero before rounding. Negative zero is normalized for display so the result does not suggest a directional change that is not present at that precision.
Read the speed unit with the row
The speed table uses a consistent indicated and theoretical unit for each row. A ratio calculation works in either km/h or mph. Converting speeds uses the exact international-mile relationship of 1.609344 km per mile.
Use machine values for further calculations
CSV numeric fields use a decimal point and explicit unit columns. Localized labels do not alter stable field identifiers. JSON preserves numeric inputs and settings. If you need to reproduce a result, use those source values instead of numbers rounded in a PDF.