RollingSpecWheel Offset Calculator
Compare a current and a new wheel's width and offset to estimate inner clearance change, outward poke, and approximate backspacing/frontspacing.
Geometry comparison only. Results are estimates based on nominal dimensions. Fitment depends on additional factors — tire width, suspension components, fender clearance, brake caliper clearance, and manufacturer tolerances. This tool does not state whether a wheel fits or is safe for your vehicle.
What is wheel offset?
Offset is the distance from the wheel's centerline to its hub mounting surface, measured in millimeters. Positive offset places the mounting surface toward the fender side of centerline, tucking the wheel inward. Zero offset means the mounting surface sits exactly at the centerline. Negative offset places the mounting surface toward the suspension side, pushing the wheel outward.
How wheel width affects fitment
Wider wheels move both the inner and outer edges further from the mounting surface (roughly half the added width in each direction, depending on offset). This can reduce inner clearance to suspension components and increase outer poke simultaneously — width and offset changes should be evaluated together, not separately.
Offset vs backspacing
Backspacing measures the distance from the mounting surface to the wheel's inner edge, so it combines both width and offset into one number. Two wheels with the same offset but different widths will have different backspacing. This calculator shows both offset and approximate backspacing/frontspacing for direct comparison.
How to compare two wheels
Enter the width and offset for your current wheel and the new wheel you're considering. The calculator shows the inner clearance change and outer poke change in plain language, so you don't need to interpret signed offset numbers yourself.
Inner clearance vs outer poke
"Inner clearance" describes the space between the wheel/tire's inner edge and chassis or suspension components. "Outer poke" describes how far the wheel/tire sticks out toward (or beyond) the fender. A wheel change can affect both at once, in opposite directions.
Why calculator results do not guarantee fitment
This tool compares nominal geometry only. Actual fitment also depends on tire width, suspension geometry, fender clearance, brake caliper clearance, wheel spoke design, steering angle, suspension compression, alignment settings, and manufacturer tolerances. Always verify compatibility with your vehicle, wheel, and tire manufacturers or a qualified professional before purchasing or installing wheels.
Changing tire sizes along with your wheels? Compare the geometry with theTire Size Calculator.
FAQ
What is wheel offset?
Offset is the distance in millimeters from the wheel's centerline to its hub mounting surface. Positive offset moves the mounting surface toward the outside (fender side), which tucks the wheel further inward. Negative offset does the opposite, pushing the wheel outward.
What does ET35 mean?
ET is short for "Einpresstiefe" (German for insertion depth). ET35 means an offset of +35 mm.
Does lower offset push the wheel outward?
Yes. A lower (or negative) offset moves the wheel's mounting surface toward the suspension side relative to centerline, which pushes the wheel body further outward (more poke) toward the fender.
How do I convert offset to backspacing?
Approximate backspacing (in inches) equals half the wheel width plus the offset in millimeters divided by 25.4. This calculator does the conversion automatically and shows it labeled as an approximation.
Will a different offset wheel fit my car?
This calculator only compares nominal geometry. Whether a wheel physically fits depends on additional factors: tire width, suspension components, fender clearance, brake caliper clearance, spoke design, steering angle, suspension travel, alignment, and manufacturer tolerances.
How much will my new wheels stick out?
The "outer position (poke) change" figure above estimates how much further outward (or inward) the new wheel's outer edge sits compared to the current wheel, based on the width and offset you entered.