How calculations are checked
The calculator engines use documented equations with bounded inputs and deterministic outputs. Release checks include formula test cases, manual spot calculations, unit-conversion checks, positive and negative offset cases, and responsive browser testing.
Precision and rounding
Full numeric precision is preserved during calculations and values are rounded only for readable display. Small display differences can therefore occur when a rounded value is used to manually reproduce a multi-step calculation.
Nominal versus real dimensions
Tire sidewall codes and wheel bead-seat widths are nominal specifications. Mounted tire width and diameter vary by manufacturer, model, measuring rim, pressure, load and wear. Wheel backspacing also depends on measured overall width and flange geometry.
No fitment guarantee
A favorable dimensional result does not prove a setup is safe, legal or approved. Always verify brake, suspension, fender and body clearance; hub and bolt compatibility; load and speed ratings; tire-to-rim approval; and relevant manufacturer or legal requirements.