Wheel Offset Calculator
Compare your current and new wheel specs to instantly see inner clearance, outer poke, and overall width change. Works in mm and inches.
⚙️ Wheel Specifications
Current Wheel
New Wheel
Side-view fitment diagram
📐 Fitment Results
Offset difference
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Inner clearance change
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Outer poke change
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Overall width change
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New inner position
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New outer position
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⚠️ Tire size, suspension, brake clearance, and vehicle geometry can affect actual fitment. Always test-fit before final installation.
Wheel Offset & Fitment Explained
What is wheel offset?
Wheel offset is the distance from the wheel's mounting surface (the hub face) to the centerline of the wheel. It's measured in millimeters (mm) and determines how far the wheel sits inward or outward relative to the hub. Offset directly affects inner clearance, outer poke, and how the vehicle handles.
Positive offset
A positive offset means the mounting surface is outboard of the wheel centerline. This pushes the wheel inward toward the suspension, reducing outer poke and increasing inner clearance. Most modern factory wheels have positive offsets between +35mm and +55mm.
Negative offset
A negative offset means the mounting surface is inboard of the wheel centerline. This pushes the wheel outward, increasing poke and reducing inner clearance. Deep-dish wheels often use negative offsets, giving that aggressive stance.
Wheel width
Wheel width is measured from inner bead to outer bead, typically in inches (e.g., 8.5"). A wider wheel extends further both inward and outward from the centerline, so changing width alters both inner and outer positions — even if offset stays the same.
Backspacing relationship
Backspacing is the distance from the inner edge of the wheel to the mounting surface. It's directly related to offset and width: Backspacing = (Width / 2) + (Offset / 25.4) (when width is in inches). Understanding both helps you predict clearance accurately.
Inner clearance & outer poke
Inner clearance is the space between the wheel's inner edge and suspension/brake components. Outer poke is how far the wheel extends beyond the fender. Our calculator shows how these change when switching wheels, so you can avoid rubbing or excessive poke.
Worked example
Suppose your current wheel is 7.5" wide with +40mm offset. You're considering an 8.5" wide wheel with +35mm offset.
- Current inner position: 3.75" + 1.575" = 5.325" from hub face inward
- Current outer position: 3.75" − 1.575" = 2.175" outward from hub face
- New inner position: 4.25" + 1.378" = 5.628" inward → 0.303" (7.7mm) more inner clearance needed
- New outer position: 4.25" − 1.378" = 2.872" outward → 0.697" (17.7mm) more poke
- Overall width difference: +1.0" (25.4mm) total
This means the new wheel will sit 0.303" closer to suspension and poke 0.697" further out. Check for rubbing and fender clearance.
Wheel fitment limitations
Offset and width alone don't guarantee fitment. Tire sidewall shape, suspension travel, brake caliper size, fender shape, and camber all play a role. Always test-fit and consult a professional if unsure.
Frequently Asked Questions
What is the difference between offset and backspacing? ▼
Offset is the distance from the wheel's centerline to the mounting surface, in mm. Backspacing is the distance from the inner edge to the mounting surface, usually in inches. They're related: Backspacing = (Width/2) + (Offset/25.4).
Can I use this calculator for any vehicle? ▼
Yes, the math is universal. However, actual fitment depends on your specific vehicle's suspension, brakes, and fenders. Always test-fit.
Does a wider wheel always increase poke? ▼
Not always. A wider wheel with a higher positive offset can actually reduce poke or keep it similar. It depends on both width and offset changes.
How do I convert inches to mm for offset? ▼
Multiply inches by 25.4. For example, 1 inch = 25.4mm. Our calculator automatically handles width in inches and offset in mm.
What is a good offset for my car? ▼
It varies by vehicle. Stock offsets are usually designed for proper clearance. Aftermarket wheels often use slightly lower offsets for a more aggressive look, but check clearance.
Can I run negative offset wheels? ▼
Yes, but negative offset pushes wheels outward, which can cause tire rubbing and poor handling. It's common in off-road and stance builds with modifications.
How accurate is this wheel offset calculator? ▼
The geometry is mathematically accurate. However, real-world fitment depends on tire bulge, suspension compression, and manufacturing tolerances. Use it as a guide.
Why does my tire rub after changing offset? ▼
Changing offset alters the wheel's position relative to suspension and fenders. A lower offset moves the wheel outward, which can cause tire-to-fender contact, especially with wide tires or lowered suspension.