Real numbers for real builds.
Fast automotive calculators for tire sizing, wheel fitment, gearing, fuel cost, engine math and performance estimates. No account, no spreadsheet, no forum archaeology.
Garage tools
Use the calculators for quick estimates, then verify critical measurements and specifications before ordering parts or modifying a vehicle.
Tire Size Calculator
Compare diameter, circumference, ride-height change and speedometer error.
Wheel Offset Calculator
See how width and offset change inner clearance and outer poke.
Fuel Cost Calculator
Estimate trip fuel, trip cost and annual fuel spending.
Power-to-Weight
Calculate horsepower per ton and pounds per horsepower.
RPM & Speed Calculator
Estimate road speed from RPM, tire diameter and gearing.
Engine Displacement
Calculate cubic inches and liters from bore, stroke and cylinder count.
Quarter-Mile Estimator
Estimate quarter-mile ET and trap speed from weight and horsepower.
Injector Size Calculator
Estimate injector flow needed from horsepower, BSFC and duty cycle.
Compression Ratio
Estimate static compression ratio from engine dimensions and chamber volume.
Wheel Backspacing
Convert wheel width and offset into a nominal backspacing estimate.
Learn the math behind the build
GarageMath guides explain the formulas, tradeoffs and common mistakes behind the calculators.