Wheel Offset Calculator
Compare your current and new wheel specs to see how inner suspension clearance and outer flush will change — with a real-time visual diagram. Enter wheel width and ET offset below.
How it works: Wheel offset (ET) is the distance in mm from the wheel's centerline to its hub mounting face. A higher ET positions the wheel further inward (more tucked). A lower ET moves the wheel outward (more flush or protruding). This tool shows exactly how much your fitment changes.
Current Wheel
New Wheel
Inner Clearance Change
—
space toward suspension
Outer Position Change
—
flush toward fender
Cross-Section — Centerline & Offset Visualized Live
Current wheel
New wheel
Hub / mount face
Common Stock Offsets Reference
| Vehicle | Stock Width | Stock ET | Common Upgrade |
|---|---|---|---|
| BMW M3 E9X (front) | 8.0" | +35mm | 9.0" ET25–30 |
| BMW M3 E9X (rear) | 9.0" | +23mm | 10.0" ET18–22 |
| BMW X5 (E70/F15) | 8.5" | +46mm | 9.5" ET35–40 |
| Honda Civic (10th gen) | 7.0" | +55mm | 8.0" ET42–48 |
| Honda CR-V | 6.5" | +50mm | 7.0" ET42–46 |
Shopping for wheels or BMW M parts? Iconic Garage carries performance suspension, brakes, and more for the BMW M3 E9X.
Understanding Wheel Offset (ET)
Wheel offset — measured in millimeters and often labeled "ET" from the German Einpresstiefe — defines where the wheel sits relative to the hub. Positive ET places the hub contact face toward the outside of the wheel (common on front-wheel-drive cars). Negative ET places it toward the inside (common on trucks and off-road vehicles).
When you change to a wider wheel or a lower offset, the wheel moves outward — which can improve the stance but may cause rubbing on the fender liner. Changing to a higher offset moves the wheel inward, reducing inner clearance against the strut housing or brake caliper.
How This Calculator Works
The calculator computes two values using the formula: Inner Clearance Change = (old width − new width) × 12.7 + (new ET − old ET). A positive result means you gained inner clearance; negative means you lost it. The Outer Position Change = (new width − old width) × 12.7 + (new ET − old ET) — positive means the wheel protrudes further outward.
Frequently Asked Questions
What is a safe inner clearance change? +
Generally, losing up to 5–8mm of inner clearance is considered safe on most vehicles, but this depends on the car. Always check clearance with the wheel turned lock-to-lock and with the suspension compressed. Values beyond –15mm may cause contact with the strut or caliper.
What does a positive outer position change mean? +
A positive outer position change means the new wheel protrudes further outward than the current one. This can look great (more flush or "poke"), but too much protrusion beyond the fender may cause rubbing on the fender lip or liner — especially at full steering lock or under suspension compression.
Can I use wheel spacers instead of changing offsets? +
Yes — a spacer of thickness X mm has the same effect as reducing your wheel's ET by X mm. For example, a 10mm spacer on an ET35 wheel is equivalent to an ET25 wheel of the same width.
Does the bolt pattern matter for this calculation? +
Bolt pattern (PCD) determines whether a wheel physically mounts to your hub — it doesn't affect the offset calculation. Always confirm your bolt pattern before purchasing new wheels.
Is this calculator accurate enough to guarantee fitment? +
No calculator can guarantee fitment. Fender liner shape, brake caliper size, suspension geometry, and tire width all affect real-world clearance. Always test fit before finalizing a wheel purchase, or consult a fitment specialist.
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