Free Wheel Offset Calculator & Fitment Comparison Tool
Compare your current wheel setup to a new configuration and instantly see how offset, width, and spacer changes affect poke, stance, and clearance. Share your results with a unique URL.
Calculate Wheel Offset Differences
Enter your wheel specifications to see how offset changes affect fitment
Understanding Wheel Offset, Backspacing & Spacers
Wheel offset—often stamped as “ET” (from the German Einpresstiefe)—is the distance in millimeters from the wheel’s hub mounting surface to the true centerline of the rim. It determines how far inward or outward the wheel and tire assembly sits relative to the hub face, directly affecting stance, fender clearance, suspension geometry, and even steering feel. Spacers add another layer of adjustment by effectively reducing offset and pushing wheels outward.
Positive Offset (Higher ET)
With a positive offset the hub mounting surface sits toward the street-facing side of the wheel. This tucks the wheel and tire deeper into the fender well, closer to the strut or coil-over. Most factory vehicles—especially passenger cars and crossovers—run positive offsets between ET30 and ET50. Higher positive offset keeps the scrub radius small for stable, predictable steering.
Negative Offset (Lower ET)
A negative offset pushes the hub mounting surface behind the centerline, moving the wheel outward past the fender lip. This creates an aggressive, “deep-dish” look popular on lifted trucks, Jeeps, and off-road builds. Be aware that aggressive negative offsets increase the scrub radius, add leverage on wheel bearings, and can cause tires to rub on fenders during turns or suspension travel.
Zero Offset & Centerline
Zero offset means the mounting surface is exactly at the wheel’s centerline. It serves as the neutral reference point: any value above zero is positive offset, and any value below is negative. Many classic truck wheels and aftermarket deep-lip wheels sit at or near zero offset.
How Wheel Spacers Work
A spacer bolts between the hub and the wheel, physically pushing the wheel outward. A 25 mm spacer on a wheel stamped ET45 gives you an effective offset of ET20. Spacers are a cost-effective way to widen your track or clear brake calipers without buying entirely new wheels. Always use hub-centric spacers with the correct bolt pattern and torque specs.
Offset vs. Backspacing
Backspacing measures from the wheel’s inner lip to the mounting surface, while offset measures from the centerline to the mounting surface. Converting is straightforward: Backspacing = (Wheel Width × 25.4 / 2) + Offset. Both numbers describe the same geometry from different reference points. If you know your backspacing, our calculator can help you find the matching offset.
Fitment & Safety Considerations
Changing offset by more than 10–15 mm in either direction can affect fender clearance, turning radius, ABS sensor alignment, and tire wear patterns. Always test-fit at full steering lock and full suspension droop before committing. For lifted trucks or aggressive builds, consult a professional—Platinum Wheels offers free fitment consultations at our Denver shop.
How to Use the Wheel Offset Calculator
- Enter your current wheel specs – width (inches), offset / ET (mm), and spacer thickness if any.
- Enter the new wheel specs you’re considering.
- Hit “Calculate Differences” – the tool instantly shows offset change, poke difference, and a visual cross-section diagram.
- Share the URL – after calculating, the page URL updates with your specs so you can copy it and send it to a friend, your installer, or post it in a forum.
Frequently Asked Questions About Wheel Offset
What offset do I need for a flush fitment?
A “flush” look typically requires the outer lip of the tire to sit nearly even with the fender. The exact offset depends on your vehicle’s hub width, fender arch, and tire size. Use our calculator to compare a few options, then bring the results to our Denver shop for a professional recommendation.
Will changing my wheel offset void my warranty?
Manufacturer warranties vary. Minor offset changes (5–10 mm) are generally considered safe and rarely affect warranty coverage. Extreme changes that cause accelerated wear or component damage could be a different story—always check with your dealer.
Can I run spacers instead of buying new wheels?
Yes. Quality hub-centric spacers are a safe and affordable way to effectively lower your offset. Make sure they match your bolt pattern and hub bore, and re-torque after the first 50 miles.
What is wheel poke?
“Poke” refers to how far the wheel/tire extends past the fender. A positive poke change means the wheel moves outward (more aggressive), while a negative poke change means it tucks inward (more conservative). Our calculator computes poke change in both millimeters and inches.
Need Expert Wheel Fitment Advice?
Our Denver team specializes in custom wheel fitment. We’ll help you find the perfect offset, width, and setup for your vehicle. Free consultations available.