Free · Transportation calculators 🚘

Wheel Width & Offset Position Comparison

Compare changes in a wheel’s inner reach and outer position from width and signed offset.

Formula & worked example
Private in your browser
No signup

Go to tool

Calculator inputs

Loading calculator…

How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Changing from a 7-inch wheel at +40 mm offset to an 8-inch wheel at +35 mm moves the modeled inner edge 7.7 mm farther inward and the outer edge 17.7 mm farther outward.

Inner reach = width/2 + offset; outer reach = width/2 − offset; reported change = old reach − new reach

Worked example

Enter these known values and leave the other values blank.

Existing wheel width: 7 in
Existing signed offset: 40 mm
Replacement wheel width: 8 in
Replacement signed offset: 35 mm

Inner clearance change (positive means more space): -7.7 mm
Outer position change (negative means farther out): -17.7 mm

Assumptions and limitations

Offset is signed relative to the wheel centerline. Positive, zero and negative offsets are valid; both widths must be positive.
A positive inner-clearance change means the replacement reaches less far inward. A negative value means it reaches farther inward and reduces the modeled clearance.
The outer-position result also uses old minus new reach. A negative value means the replacement extends farther outward; a positive value means it moves inward.
Use the same width convention for both wheels. Nominal bead-seat width excludes rim-flange details; this model does not reconstruct their outermost edges.
This is a dimensional comparison, not a fitment approval. Tire section width, flange profile, brakes, suspension travel, steering motion, hub geometry and required clearances need separate checks.

Common questions

Can a wheel have zero or negative offset?

Yes. Zero puts the mounting face on the centerline. A negative offset puts it toward the inner side relative to that line.

Why is an outward movement shown as a negative number?

The retained formula subtracts the replacement outer reach from the existing reach. A larger replacement reach therefore produces a negative change.

References

Bookify allows zero and negative wheel offsets. The captured source incorrectly restricted both offsets to positive values.

Explore transportation calculators 🚘 or browse all everyday life calculators.