MyWheelOffsetCalculator
Guide

Wheel Offset Calculator

Compare wheel widths, offsets, and backspacing with our top-down visual cross-section diagram. Identify clearance changes against your suspension struts and fender lips before buying aftermarket rims.

Units:
Setup ACurrent / Stock
8"
in
+35 mm
mm
in
Backspacing:5.38"
Frontspacing:2.62"
Setup BNew / Proposed
9"
in
+22 mm
mm
in
Backspacing:5.37"
Frontspacing:3.63"
Vehicle Clearances (optional)Measures Setup A to draw strut & fender to scale
in
in

Top-Down Wheel Cross-Section

Inner suspension strut (left) vs. Outer fender lip (right)

Fender and strut positions are illustrative. Enter clearances to draw to scale.

Likely rubbing, verify fitment
Outer poke increased by 26 mm (>20 mm)Actual rubbing depends on the car, fender, suspension travel, and tire size. Thresholds are rules of thumb.
Strut / ShockFender LipHUB FACE (0 mm)+1.01" poke← SUSPENSION (INNER)FENDER (OUTER) →
Old: 8" ET+35
New: 9" ET+22
Hub Face (0mm)
Old centerline
New centerline
Add tire width to see tire clearance
Shift:Your new wheel sits 26 mm further out (more poke) and has no meaningful change in inner room.
Insight:Wider wheel + lower ET: the inner edge barely moves, so all the extra width goes outside.
Fitment Shift Verdict

Your new wheel sits 26 mm further out (more poke) and has no meaningful change in inner room.

Rim-only estimate. Add tire width for a more realistic result.
Suspension / Inner Clearance
0 mm
No meaningful change
Outer Fender Position (Poke)
+1.01"
26 mm further out (more poke)
Estimates only. Always dry test-fit before mounting tires.
Dual Fitment (front vs rear / staggered) calculator →

Specialized Fitment Calculators

Backspacing Calculator

Convert wheel offset (ET mm) directly into imperial backspacing and frontspacing.

Wheel Spacer Calculator

Calculate effective offset and verify minimum lug stud thread engagement turns.

Tire Size Comparison

Compare overall diameters, revs per mile, and calculate speedometer calibration drift.

Bolt Pattern Database

Filter and search PCD specs, lug patterns, and center bore data across hundreds of vehicles.

Wheel Fitment Overview

What Is Wheel Offset?

Wheel offset (universally stamped as ET, from the German Einpresstiefe) is the distance in millimeters from the wheel's geometric centerline to the hub mounting face that bolts against your brake rotor. Offset directly controls whether your wheels tuck deep inside the wheel wells or push out toward the fender.

The Golden Rule of Wheel Offset

Lower Offset = More Poke (Outward). Higher Offset = More Tuck (Inward). Lowering the ET number pushes the wheel rim toward the fender arch, while raising the ET number pulls the wheel deeper toward your inner suspension struts.

Offset TypeStamped ExampleHub Pad LocationVisual Stance
Positive (+ET)ET+35 to ET+55Outward towards street faceFlat/convex spokes, tucked in fender (modern FWD/AWD)
Zero (ET 0)ET 0Exact centerline of rimBalanced dish (vintage muscle cars, classic trucks)
Negative (−ET)ET-10 to ET-44Behind the wheel centerline, toward the inside of the wheelDeep-dish lip, aggressive poke (lifted 4x4s, widebody builds)

Worked Fitment Example: 18x8 +35 to 18x9 +22

Upgrading from 18x8.0" ET+35 to 18x9.0" ET+22 adds 1.0" of width (12.7 mm each side) and reduces offset by 13 mm. Outer poke increases by +25.7 mm (12.7 mm width + 13 mm offset), while inner strut clearance changes by only −0.3 mm (12.7 mm width − 13 mm offset), maintaining safe suspension clearance.

Read the Full Wheel Offset Guide
Related Fitment Guides
Backspacing Explained →Negative vs Positive Offset Wheels →Wheel Spacers & Offset →How to Fix Wheel Rubbing →Offset & Handling Dynamics →
Fitment FAQ

Frequently Asked Wheel Offset Questions

What is wheel offset and how does it work?

Wheel offset (ET) is the distance in millimeters from the wheel's geometric centerline to the hub mounting face contacting the brake rotor. A positive offset positions the mounting face towards the street face, pulling the wheel inward toward suspension parts. A negative offset pushes the wheel outward toward the fender for a wider stance. Learn more in our comprehensive [wheel offset guide](/guides/what-is-wheel-offset).

Does a lower offset make the wheel stick out more?

Yes. Lower numerical offset values push the wheel further outward toward the vehicle fender lip (more poke). If wheel width remains identical, every 1 mm reduction in offset results in exactly 1 mm more outer poke and 1 mm additional inner suspension clearance.

How does wheel width affect inner and outer clearance when offset changes?

Whenever wheel width increases, the added width splits equally on both sides of the centerline (12.7 mm inward and 12.7 mm outward for every 1.0 inch). The resulting clearance shift combines this width expansion with your offset change to determine final strut and fender clearance.

How do I know if my new wheels will rub on the suspension or fender?

Use our calculator above to check your setup's rubbing risk score based on inner and outer clearance shifts. Before driving, always dry test-fit bare rims and check clearance at full steering lock and suspension compression. If rubbing occurs, see our [guide to fixing wheel rubbing](/guides/how-to-fix-wheel-rubbing).

What is the difference between wheel offset and backspacing?

Offset is measured from the rim centerline in millimeters, while backspacing is measured from the hub pad to the extreme inner lip in inches. The conversion formula is: backspacing (inches) = width / 2 + offset / 25.4 (for example, an 8" ET+35 wheel equals 5.38" backspacing). For conversions, see our [Backspacing Calculator](/backspacing-calculator) and [Backspacing Guide](/guides/what-is-backspacing).

Do wheel spacers change the offset of a wheel?

Wheel spacers do not physically alter the machined wheel itself, but they change the effective offset of the assembly. Installing a 15 mm spacer on a +45 mm offset wheel produces an effective offset of +30 mm, pushing the wheel 15 mm outward. Verify safe lug bolt engagement with our [Wheel Spacer Calculator](/wheel-spacer-calculator) and [Wheel Spacer Guide](/guides/do-wheel-spacers-change-offset).