You need a tape measure, a helper, and five minutes. Measure in inches to the nearest ⅛ in and write down your truck's year, make, model, cab and bed.
1. Rail length (the one shell makers want)
Along the top of the bed rail, from the inside of the front bed wall to the inside of the closed tailgate. This is usually a little longer than the floor length on our charts because the front wall of many beds leans forward.
2. Floor length
On the floor, from the front wall to the closed tailgate. This is the number on our tables and what matters for cargo.
3. Outside rail width
Across the top of the bed, from the outside edge of one rail to the outside edge of the other, at the front and again at the tailgate. Shells sit on this surface, so if the beds taper, both numbers matter.
4. Width between the wheel wells
The narrowest spot on the floor. About 50 in on full-size trucks — just enough for a 48 in sheet of plywood — and 41–45 in on mid-size trucks.
5. Depth
From the floor to the top of the rail, at the side wall. Needed for drawer systems, toolboxes and how much of your load sits below the rails.
6. Cab height above the rail
From the top of the bed rail to the highest point of the cab roof. A cab-high shell should match this within about an inch, or it'll look off and catch wind.
Send us your numbers
Owner measurements help us check and correct the site. Submit your measurements — especially if you drive a truck we list as "spot-check."