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Wheel offset calculator

This wheel offset calculator shows how wheel and tire move when offset, rim width or tire width change: how many millimeters more room do the fender and the suspension need, and how does the track width change?

Example: Old wheel width (J) 7 in · Old offset (ET) 45 mm · Old tire width 205 mm · New wheel width (J) 8 in · New offset (ET) 35 mm · New tire width 225 mm → Shift: Outside +20 mm · inside 0 mm. Source: Wikipedia – Wheel offset (definition of ET/offset, effect on wheel arch and axle). Updated: .

in
e.g. 7 for 7J × 16
mm
stamped on the wheel, e.g. ET45; positive offset puts the mounting face toward the outside
mm
first number of the tire size, e.g. 205 in 205/55 R16; 0 = ignore
in
mm
mm
0 = ignore
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Result

Shift
Outside +20 mm · inside 0 mm
Inside and outside compared
PartInside (toward suspension)Outside (toward fender)
Wheel+2.7+22.7
Tire0+20
How to read the result
  • Track width per axle: +20 mm (each wheel moves outward by half the change).
  • Inside: a plus value means it reaches closer to the strut and brakes, a minus value means more room to the suspension.
  • Outside: a plus value means it reaches closer to the fender, a minus value means it sits further in.
  • The tire row uses tire width; the wheel row uses wheel width.
Calculated values for wheel and tire at wheel center; real clearance depends on tire shape, suspension travel and steering lock. Approval and registration of new wheels follow the rules of your country.

How it is calculated

With an offset 10 mm lower, the wheel sits 10 mm further out and the track gets 20 mm wider per axle. The wheel offset calculator shows this for your old and new values, separately for wheel and tire.

What offset means

Offset (ET, from German “Einpresstiefe”) is the distance from the hub mounting surface to the wheel's centerline, in millimeters. A positive value means the mounting surface sits toward the outer edge, so the wheel sits further in. A lower or negative value pushes the wheel outward.

How it is calculated

Wheel width J is converted from inches at 25.4 mm; only differences count, so the thickness of the rim lip does not matter. A different offset also changes the scrub radius and loads the wheel bearings differently.

Related tools: tire size calculator, braking distance and the inch to cm converter.

Frequently asked questions

What does ET mean on wheels?

ET (from German “Einpresstiefe”) is the distance from the hub mounting surface to the wheel centerline in millimeters. The lower the ET, the further out the wheel sits.

What does a lower offset do?

For every millimeter lower offset the whole wheel sits one millimeter further out: more room on the inside toward the suspension, less on the outside toward the fender. ET 35 instead of 45 pushes the wheel out by 10 mm.

What changes with a wider wheel?

The wheel grows on both sides by half the extra width. A wheel one inch wider (25.4 mm) reaches 12.7 mm further out on each side.

Does a different offset change handling?

Yes, it changes the scrub radius and the load on the wheel bearings. That is why deviations from the manufacturer's figure need care.

Can I fit any wheels I like?

No. Permitted sizes, offsets and any registration duty are set by the rules of your country and the manufacturer's approval; the calculator is no substitute for a check.

Sources and legal basis

As of: · Editorial policy

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