Tire size calculator

Turn width, aspect ratio and rim diameter into theoretical unloaded dimensions.

Theoretical diameterEnter values to calculate

What the label describes

For 225/45R17, the sidewall is 45% of 225 mm. Two sidewalls plus the 17-inch rim produce the theoretical overall diameter.

Label geometry is not a fitment check

Actual mounted dimensions, approved rim widths, load capacity, clearance and compatibility come from the tire, wheel and vehicle manufacturers.

More tools

Tire comparison

Compare the geometry of two metric tire labels.

Speedometer error

Estimate geometric speed change from tire diameter.

RPM & road speed

Relate speed and RPM through tire and gear ratios.

Two-stroke mix

Calculate oil from a manufacturer-specified ratio.

Wheel offset

Compare inner clearance and outer wheel position.

Compression ratio

Calculate static ratio from cylinder and clearance geometry.

Engine displacement

Calculate total displacement from bore, stroke and cylinders.

Power to weight

Compare horsepower and vehicle weight in common units.

Sprocket ratio

Find chain-drive ratio and driven sprocket RPM.

Injector size

Estimate per-cylinder fuel flow from explicit assumptions.