Wheel Offset & Backspacing Calculator
Compare wheel setups or convert between offset and backspacing. See if your new wheels will poke, tuck, or sit flush.
What is wheel offset?
Wheel offset is the distance in millimeters between the wheel's hub-mounting surface and the centerline of the wheel. It determines how far in or out your wheel and tire package sits relative to your vehicle's fender. Positive offset pushes the wheel inward (toward the suspension), while negative offset pushes it outward (toward the fender or beyond).
When shopping for aftermarket wheels, offset is one of the most critical specs to get right. The wrong offset can cause rubbing against fenders, interfere with suspension components, or change your vehicle's handling characteristics. Offset Wiz helps you compare your stock and new setups instantly so you can make an informed decision before buying.
Offset vs. backspacing
Offset and backspacing both describe wheel fitment, but from different reference points. Offset measures from the wheel centerline to the mounting surface, expressed in millimeters. Backspacing measures from the rear lip of the wheel to the mounting surface, expressed in inches. You need to know the wheel width to convert between the two.
The formula is simple: backspacing = (wheel width / 2) + (offset / 25.4). So an 8-inch wide wheel with +45mm offset has 4 + 1.77 = 5.77 inches of backspacing. Offset Wiz handles this math for you in the converter tab.
Frequently Asked Questions
What is wheel offset?
Wheel offset is the distance in millimeters from the hub-mounting surface to the centerline of the wheel. Positive offset means the mounting face is closer to the outside (street side) of the wheel. Negative offset means it's closer to the inside (suspension side). Zero offset means the mounting surface is exactly at the centerline.
What is backspacing?
Backspacing is the distance from the back edge (inner lip) of the wheel to the mounting surface, measured in inches. Higher backspacing means the wheel sits further inside the wheel well. It's an older measurement that's still commonly used, especially in the truck and off-road world.
Will my new wheels poke or tuck?
Use the Compare Setups calculator above. Enter your stock wheel width and offset, then your new wheel's width and offset. Offset Wiz will calculate exactly how much further out (poke) or in (tuck) your new setup will sit compared to stock, measured in both millimeters and inches.
How much offset change is safe?
As a general guideline, staying within about 10–15mm of your stock offset is usually safe for most vehicles. Going further can affect steering feel, scrub radius, and wheel bearing life. Always check vehicle-specific forums and consult a wheel fitment specialist for your exact make and model.
Does tire width affect offset?
Tire width doesn't change the offset value itself — offset is a property of the wheel. But a wider tire will extend further both inward and outward from the wheel's lip, which can cause rubbing even if the offset is unchanged. Always consider the full wheel-and-tire package when evaluating fitment.