How To Measure Your Truck

The following instructions generally work well when measuring a full-size truck. Mid-size and compact trucks have a variety of truck bed configuration which increases the difficulty in measuring the truck and comparing it to the dimensions of a specific truck box.

The truck bed needs to be measured for two reasons:

  1. To determine that the truck box will be long enough to be properly mounted on the truck bed rails.
  2. To determine whether or not the truck wheel wells will interfere and prevent proper mounting of the truck box.
Dimension A

A: Determining that the truck box is long enough to be properly mounted:

Measurement 1:

Width between the top of the bed sidewalls of the crossover truck box needs to be at least 3" greater. This is called Dimension "A".

B. Determining whether or not the truck box will clear the wheel wells in the truck. Need to find Point "X" in the truck bed:

Preparing to take Measurements 2 & 3 to find a Point "X" in the truck bed to ensure that the truck box will fit your truck:

  • The depth of the truck box may restrict its fit in the truck because the wheel well might be in the way.
  • Except for "Extra-Wide" truck boxes, most truck boxes will require 20¼" of horizontal space from the cab bed rail to the point where the truck box might hit the wheel well or the truck bed liner.

Measurement 2:

Dimension C

A "Standard" truck box will usually have a 9" vertical depth below the top of the truck bed rail. A "Deep" model will usually be 12" below the top of the bed rail.

  • Determine how deep a truck box you need and measure down from the top of the rail and create an imaginary, horizontal line at the depth of the truck box you need. Usually 9" or 12" below the top of the truck bed rail. This is called Dimension "C" on the truck box.

Measurement 3:

Dimension E

Find Point "X" which is on the horizontal "Imaginary Line" below the truck rail (from 2" above).

On the horizontal "Imaginary Line", measure to find a point 20¼" away from the front truck bed rail (This measurement is from the cab truck bed rail towards the tailgate).

The 20¼" is roughly Dimension "E" on the truck box and represents how much space the truck box will take in the bed behind the truck cab.

After finding Point "X" in your truck bed, will the truck box fit?

Again, Point "X" is 20¼" away from the front truck cab rail on the imaginary horizontal line (from measurement 2)

If Point "X" does not hit the wheel well, the truck box will fit.
If Point "X" hits the wheel well, you must take another measurement:

  • Mark Point "X" on both wheel wells or the wheel well bed liner.
  • Measure the distance between the two Point "X" on the truck bed. This dimension must be greater than Dimension "B" on the truck box.
  • If Dimension "B" on the truck box is greater than the distance between both points "X", the truck box will hit the wheel well or bed liner and you will usually need to select another truck box or mount the truck box with a spacer above the bed rail.