Compare wheel width and offset

Enter four values

Provide the original width and ET, then the new width and ET. Width must be positive and within the supported range. ET may be negative, zero or positive. Keep the sign shown in the wheel’s specification; the calculator must not turn negative ET into a positive magnitude.

Supported wheel inputs

Wheel width accepts 1–20 inches and offset accepts −200 to +200 mm, including the endpoints. Decimal values use a decimal point. These broad numerical bounds make the calculation explicit; they are not a list of commercially available wheels or a statement that an extreme combination can be installed.

Read the fixed mounting plane

The diagram fixes the mounting plane at zero for both wheels. It uses the stated rim width to place an inner and an outer reference boundary. The wheel centerline moves when ET changes. The drawing labels the inside and outside directions.

Interpret both output phrases

More nominal inner space means the new inner reference reaches less far inward. Less nominal inner space means it reaches farther inward. Farther out or farther in describes the outer reference separately. Neither phrase asserts actual clearance.

Check the example before your own comparison

8 in ET45 to 8.5 in ET35 should show 3.65 mm more nominal inner space and 16.35 mm farther out. The inward distances are 146.60 and 142.95 mm; the outward distances are 56.60 and 72.95 mm. Use these values to verify that the sign convention is the one you intend.

Keep physical checks separate

The model does not include rim lips, an inflated tire’s section profile, brake shape, bolt pattern, hub bore or moving suspension. A project stores the geometric inputs, not a fitment inspection.

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