What does wheel offset (ET) mean?

Wheel offset, shown as ET (from the German Einpresstiefe, meaning insertion depth), is the distance in millimetres from the wheel's hub mounting face to the centreline of the wheel. A positive ET means the mounting face is closer to the outside of the wheel, so the wheel sits further inward toward the suspension and engine bay. A negative ET means the mounting face is closer to the inside of the wheel, so the wheel sticks further outward. Zero ET means the mounting face sits exactly at the centreline. Most modern passenger cars have a positive ET, commonly between ET35 and ET50.

What is wheel backspacing?

Backspacing is the distance from the hub mounting face to the innermost edge (back lip) of the wheel, measured in millimetres or inches. It tells you how much of the wheel sits inside the wheel arch. The formula is: Backspacing = (Total wheel width / 2) + ET offset. A wider wheel or lower ET value will reduce backspacing, meaning the wheel protrudes further outward. Backspacing is commonly used in the US and off-road fitment, while ET offset is the standard in Europe, Australia and New Zealand.

What is poke and how do I calculate it?

Poke refers to how far the outer edge of a wheel extends beyond the hub mounting face. It is calculated as: Poke = (Wheel width / 2) - ET. A wheel with width 225 mm (about 8.86 inches, close to a 9J rim) and ET35 would have a poke of (225 / 2) - 35 = 77.5 mm, meaning the outer face of the wheel is 77.5 mm outboard of the hub. Higher poke values mean the wheel sticks out further. Negative poke means the wheel is tucked inward.

Wheel Offset Calculator

Calculate ET offset, backspacing and poke for any wheel fitment. Enter your wheel width and ET value to see exactly how far the rim sits inward or outward. Compare old and new fitments to find the position change.

All measurements in millimetres. ET (Einpresstiefe) is the standard offset unit used in New Zealand, Australia, and Europe.

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Standard Formula Backspacing = (wheel width ÷ 2) + ET. Poke = (wheel width ÷ 2) − ET.

1. Current Wheel

Wheel width (mm, measured bead to bead)

ET offset (positive = inward, negative = outward)

Common ET presets

2. New / Aftermarket Wheel

Wheel width (mm)

ET offset

Common ET presets

Wheel Position Results

Current Backspacing

Hub face to inner lip

New Backspacing

Hub face to inner lip

Outward Position Change
-
Per wheel (+ = outward)

New Poke

Outer face from hub centre

Current Wheel Breakdown

Width-

ET offset-

Half width (centreline)-

Backspacing-

Poke (outer face from hub)-

Inset (inner face from hub)-

New Wheel Breakdown

Width-

ET offset-

Half width (centreline)-

Backspacing-

Poke (outer face from hub)-

Inset (inner face from hub)-

Position Change Summary

	Current Wheel	New Wheel	Change
Backspacing	-	-	-
Poke	-	-	-
Inset	-	-	-
Outward position	-	-	-

Fitment note: Enter your wheel details above.

How Wheel Offset Works

Wheel offset (ET) is the distance in millimetres from the hub mounting face to the centreline of the wheel. It controls how far inboard or outboard the wheel sits in the wheel arch.

Key measurements:
Backspacing (mm) = (Wheel Width / 2) + ET
Poke (mm) = (Wheel Width / 2) - ET
Inset (mm) = ET (positive ET = wheel sits further inboard)
Outward position change = (Old ET - New ET) + ((New Width - Old Width) / 2)

Positive and Negative Offset Explained

ET Value	Mounting face position	Wheel position	Typical use
Positive (e.g. ET45)	Closer to outside face	Tucked inward (more clearance)	Most modern passenger cars
Zero (ET0)	At centreline	Neutral	Some older and off-road vehicles
Negative (e.g. ET-15)	Closer to inside face	Sticks outward (poke or flush)	Modified, off-road, and wide-body builds

Backspacing vs ET Offset

ET offset is the European standard and is stamped on most wheels sold in New Zealand. Backspacing is the US standard and is commonly used in the off-road and truck fitment market. Both describe the same physical measurement from different reference points. If you know one, you can calculate the other using the wheel width:

Backspacing (mm) = (Width / 2) + ET. To convert to inches, divide by 25.4.

ET from backspacing: ET = Backspacing - (Width / 2).

What is Poke?

Poke is the distance the outer face of the wheel sits outboard of the hub mounting face. It is calculated as: Poke = (Width / 2) - ET. A wheel with a high positive ET has less poke and sits more inboard. A lower or negative ET increases poke, making the wheel flush with or beyond the guard lip. Many car enthusiasts aim for a specific poke value to achieve a flush or aggressive stance without the wheel rubbing on the guard or suspension components.

Worked Example

Default values: current wheel is 215 mm wide with ET45; new wheel is 225 mm wide with ET38.

Current backspacing: (215 / 2) + 45 = 107.5 + 45 = 152.5 mm
New backspacing: (225 / 2) + 38 = 112.5 + 38 = 150.5 mm
Current poke: (215 / 2) - 45 = 107.5 - 45 = 62.5 mm
New poke: (225 / 2) - 38 = 112.5 - 38 = 74.5 mm
Outward position change: (45 - 38) + ((225 - 215) / 2) = 7 + 5 = 12 mm outward per side

This matches the calculator's default output: each new wheel sits 12 mm further outward. The outer face moves from 62.5 mm to 74.5 mm outboard of the hub, which is 12 mm more poke per side.

Fitment and Guard Clearance

Moving a wheel outward increases the risk of the tyre rubbing on the guard lip or inner guard liner at full lock and over bumps. As a general guide, most vehicles can accommodate 5 to 10 mm of outward movement without modification. More than 10 mm outward usually requires checking guard clearance carefully. Moving a wheel inward (higher ET, lower poke) reduces rubbing risk but may cause the wheel to foul on brake calipers or suspension components. Always check both sides when fitting new wheels.

Converting Rim Width in Inches to Millimetres

Wheel widths are sometimes stated in inches (for example, 8J or 8.5J, where J is the flange type). To convert to millimetres, multiply by 25.4. An 8J rim has a bead-to-bead width of 8 x 25.4 = 203.2 mm. A 9J rim is 228.6 mm wide. Use the millimetre figure in this calculator.

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Sources and method: Offset formula (Backspacing = (Width / 2) + ET; Poke = (Width / 2) - ET) is the industry standard used by wheel manufacturers worldwide. ET abbreviation from German Einpresstiefe (DIN standard for wheel offset). All measurements in millimetres unless stated otherwise.

This calculator provides geometric estimates only. Always verify physical fitment clearance on your specific vehicle before driving. Guard, brake caliper, and suspension clearances vary by vehicle model and modification level. Consult a wheel fitment specialist if you are unsure.