Wheel Offset & Fitment Calculator
Compare your current wheel setup to a new setup to see how inner clearance and outer poke change.
Current Wheel Setup
New Wheel Setup
Understanding Wheel Offset and Fitment
When upgrading your vehicle's rims, understanding wheel offset is critical to ensuring the new wheels don't rub against your suspension components or stick out too far past the fenders. Offset is the distance from the hub-mounting surface to the true centerline of the wheel.
How Offset Affects Your Vehicle
Offset is measured in millimeters and can be positive, zero, or negative:
- Positive Offset: The mounting surface is toward the front (street side) of the wheel. Common on modern front-wheel-drive cars.
- Zero Offset: The mounting surface is even with the centerline of the wheel.
- Negative Offset: The mounting surface is toward the back (braking side) of the wheel. This creates a "deep dish" look and is common on trucks and older RWD cars.
Calculations Explained
Our calculator uses the following logic to determine how your new wheels will sit compared to your current ones:
Inner Clearance: This measures how much closer the inner lip of the wheel moves toward the strut or suspension. To calculate this, we convert the width to millimeters, find the distance from the hub to the inner edge, and compare the two setups. If the result is "12mm less," your new wheel is 12mm closer to the suspension.
Outer Position (Poke): This measures how much the outer face of the wheel moves toward the fender. If you increase wheel width or decrease offset, the wheel will "poke" out further. A result of "20mm more" means the wheel face will sit 20mm further out than your current setup.
Example Calculation
If you move from an 18×8 ET45 wheel to an 18×9 ET35 wheel:
- The wheel is 1 inch (25.4mm) wider.
- The offset decreased by 10mm (moving the wheel outward).
- The result: You will have 2.7mm less inner clearance and the wheel will poke out 22.7mm more than before.