Wheel Offset Calculator

Compare inner clearance and outer wheel position after a size change.

Results

Outer position change

+16.35mm

Wheel extends 16.35 mm farther outward

Current inner position: 146.6 mm
New inner position: 142.95 mm
Current outer position: 56.6 mm
New outer position: 72.95 mm
Inner clearance change: +3.65 mm3.65 mm more inner clearance

This calculator compares the geometric position of the wheel itself only. It does not account for tire width, tire sidewall bulge, brake caliper clearance, suspension geometry, fender clearance, wheel spoke shape or vehicle manufacturer limits. It cannot guarantee fitment; check the actual assembly and manufacturer specifications before installation.

Formula · How it works

Formula

Half width (mm) = Width (in) × 25.4 / 2; Inner position = Half width + Offset; Outer position = Half width − Offset; Inner clearance change = Current inner position − New inner position; Outer position change = New outer position − Current outer position

Convert wheel width to mm and divide by two. Relative to the mounting face, inner position is half width plus offset and outer position is half width minus offset. Subtract new inner position from current inner position for the inner-clearance change. Subtract current outer position from new outer position for the outward-position change.

Worked example

Changing from 8.0J ET45 to 8.5J ET35 changes inner position from 146.6 mm to 142.95 mm, giving 3.65 mm more inner clearance. Outer position changes from 56.6 mm to 72.95 mm, so the new wheel extends 16.35 mm farther outward.

How it works

A positive inner-clearance change means more clearance on the inside; a negative value means less. A positive outer-position change means the wheel extends farther outward, often called more poke; a negative value means it sits farther inward, or more tuck. Positions use the entered nominal wheel width and do not represent measured clearance to a vehicle component.

Common questions

What is wheel offset?

Offset is the distance between the wheel centerline and its mounting face, measured in mm. Positive offset places the mounting face toward the outer side, zero offset places it on the centerline, and negative offset places it toward the inner side.

What does ET45 mean?

ET45 means a positive offset of 45 mm. Enter 45 for ET45, 0 for ET0 and a negative value for a negative offset. Wheel width is entered separately in inches.

How does lower offset affect wheel position?

At the same width, lowering offset moves the wheel outward. Inner clearance increases and the outer edge extends farther outward by the same amount. Raising offset has the opposite effect.

How does wheel width affect clearance?

At the same offset, adding width extends half the added width inward and half outward. Inner clearance decreases, while the outer edge moves farther outward. Changing offset at the same time can alter either change.

Can this calculator guarantee wheel fitment?

No. It compares nominal wheel geometry, not complete wheel-and-tire fitment. Tire shape, brakes, suspension, fenders, spokes and manufacturer limits must be checked separately on the intended vehicle.