Wheel Offset Calculator
This calculator computes wheel offset and rim fitment for proper installation.
- Free online ET offset calculator for wheels and tire compatibility.
Figures are estimates from this calculator’s standard formula — adjust the inputs in the tool below for your exact number.
How Wheel Offset Calculation Works
Wheel offset is the distance from the wheel's centerline to the hub mounting surface, measured in millimeters. Positive offset means the mounting surface is toward the front (street side), negative offset pushes the wheel outward. This calculator converts between offset and backspacing.
- 1
Choose Calculation Mode
Select whether to calculate from offset or from backspacing
- 2
Enter Wheel Width
Input wheel width in inches (e.g., 8.5 inches)
- 3
Enter Offset or Backspacing
Provide offset in mm or backspacing in inches
- 4
View Fitment Data
See calculated measurements and fitment information
Use Cases
Wheel Fitment
Determine if aftermarket wheels will fit without rubbing
Stance Planning
Calculate offset needed for flush or aggressive wheel fitment
Spacer Calculation
Determine spacer thickness needed to achieve desired fitment
Clearance Check
Verify clearance for brakes, suspension, and fenders
Tips
- 1
Stay within 5-10mm of stock offset for daily drivers to maintain handling
- 2
Lower offset (more negative) pushes wheels outward for wider stance
- 3
Always check both inner clearance (suspension/brakes) and outer clearance (fenders)
- 4
Consider tire width as it affects total package clearance beyond wheel offset
- 5
Test fitment at full steering lock and suspension compression before committing
Common Mistakes
Confusing offset with backspacing - they reference different points
Not accounting for tire width when calculating total package fitment
Changing offset without checking brake caliper and strut clearance
Ignoring the effect of offset changes on handling and scrub radius
FAQs
What is the difference between offset and backspacing?
What does positive vs negative offset mean?
How much offset change is safe?
Will changing offset affect my handling?
Related tools
Pick another tool to continue your calculation.
Down Payment vs Term Trade-off
Free online tool — fast, accurate results in your browser.
Road Tax Calculator for Egypt
Free online tool — fast, accurate results in your browser.
Timing Belt Interval Calculator
Calculate timing belt replacement interval.
Car Maintenance Cost Calculator - Annual Service Tool
Calculate annual car maintenance costs and service expenses. Free online tool to estimate vehicle upkeep budget and repair costs.
MPG to L/100km Converter
Free online tool — instant, accurate conversions in your browser.
Car Insurance Calculator for United Kingdom
Free online tool — fast, accurate results in your browser.