buncha/engineering/wheel-offset

Wheel Offset Calculator

Plan a wheel swap before you buy. Plug in your current setup and the new wheels you're eyeing — get the inboard / outboard distance change, the tire diameter delta, and a head-on visual showing exactly how the wheel position and camber will sit relative to your fender.

All math runs in your browser. Nothing is uploaded.

Current setup

Diameter (in)

Width (in)

Offset (mm, ET)

Camber (°)

Tire width (mm)

Tire profile (%)

235/40R18 · 8J ET+45

New wheels

Diameter (in)

Width (in)

Offset (mm, ET)

Camber (°)

Tire width (mm)

Tire profile (%)

255/35R19 · 9.5J ET+25

Visual

Current setup

235/40R18 · 8J ET+45 · Camber -1°

New setup

255/35R19 · 9.5J ET+25 · Camber -2.5°

Side-by-side in the wheel arch

Numbers

Metric	Current	New	Δ
Wheel width	203.2 mm (8.0")	241.3 mm (9.5")	+38.1 mm
Outboard distance	56.6 mm	95.6 mm	+39.0 mm
Inboard distance	146.6 mm	145.6 mm	-1.0 mm
Tire sidewall	94.0 mm	89.3 mm	-4.8 mm
Tire outer Ø	645.2 mm (25.40")	661.1 mm (26.03")	+15.9 mm
Patch shift (camber)	5.6 mm	14.4 mm	+8.8 mm

Fender poke (outboard)

39.0 mm more poke

Outboard edge moves +39.0 mm

Inner clearance

1.0 mm more strut clearance

Inner edge moves -1.0 mm (struts, control arms)

Rolling diameter

0.63" total (+15.9 mm)

Sidewall change: -4.8 mm

Contact patch (camber)

+8.8 mm shift

At -2.5° camber the patch sits 14.4 mm from mount face

What the numbers mean

Offset (ET).Distance in mm from the hub mounting face to the wheel''s centerline. Positive ET pulls the wheel inward (more tuck). Negative ET pushes it out (more poke). ET0 = mount face is at the wheel centerline.

Inboard distance.Hub mount face to the inner edge of the wheel. Eats into your strut / control-arm / inner-fender clearance. Bigger than the original means tighter inner clearance.

Outboard distance.Hub mount face to the outer edge of the wheel. Controls how much the wheel pokes past the fender. Bigger than the original means more poke.

Camber.Vertical wheel tilt. Negative camber tilts the top inward (track / aggressive fitment look). Affects the horizontal position of the contact patch — calculator shows the shift in mm relative to the mount face.

Tire OD (rolling diameter).Wheel size + 2× sidewall. A change >3% from stock will confuse the speedometer and ABS. Calculator flags swaps that move OD by more than 20 mm.

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About Wheel Offset Calculator

Plan a wheel + tire swap before you buy. Inputs current and new wheel specs (diameter, width, offset, tire size, camber) — outputs the fitment delta (inboard / outboard shift, fender poke, tire OD change, camber contact-patch shift) and a head-on cross-section diagram so you can see exactly how the new wheel sits relative to your fender.

Like every tool on Buncha, this one runs entirely in your browser. There's no upload, no log, no record of what you've pasted or generated. Close the tab and the data is gone.

Have feedback or found a bug? hello@buncha.tools