Vehicles & Transport calculator
What Roof Bar Length Do I Need?
Use vehicle roof width at bar position, desired bar overhang each side, maximum permitted overhang each side to find roof bar length and overhang check.
Enter your measurements
What Roof Bar Length Do I Need uses vehicle roof width at bar position, desired bar overhang each side, maximum permitted overhang each side and the other configured measurements to return roof bar length and overhang check with a formula written specifically for this tool.
- Vehicle roof width at bar position — Required
- Desired bar overhang each side — Required
- Maximum permitted overhang each side — Required
Roof bar length and overhang check
Enter the measurements above to calculate roof bar length and overhang check.
How the calculation works
V9 calculation: barLength=roofWidthAtBars+2×sideOverhangEach; overhangPass=sideOverhangEach≤maxAllowedOverhang. The result is reported as roof bar length and overhang check.
Worked example
Example: Vehicle roof width at bar position = 185 cm; Desired bar overhang each side = 30 cm; Maximum permitted overhang each side = 30 cm. Result: Fits; Bar Length = 245 cm.
Before you decide
The result is only as accurate as the measurements entered. This page calculates the stated geometry or quantity only; product-specific construction or installation details can still affect the final choice. For what roof bar length do i need, the limiting result on this page is roof bar length.
Direct measurement/geometry calculation. No external reference is required for the arithmetic itself; the result is derived only from the user-entered measurements and the formula stored in calculationLogicJson.
Frequently asked questions
What does the Roof Bar Length calculator tell me?
It returns roof bar length from the measurements entered on this page. The calculation is specific to roof bar length, so the result should be compared with the exact product or specification you are considering.
Which measurements should I take for roof bar length?
Measure vehicle roof width at bar position, desired bar overhang each side, maximum permitted overhang each side. Use clear, usable dimensions rather than nominal room or product labels.
Should I round the roof bar length?
Keep the calculated value for comparison, then choose a real product that meets or stays within the returned roof bar length while allowing for the clearances, tolerances or ratings shown by its manufacturer.