How to Choose Truck Side Boxes | Fit Before You Buy

For the full breakdown, see our best Truck Side Boxes guide.

Buying a truck side box gets confusing fast, with lengths ranging from 48 inches to over 90 inches. The deciding factor isn’t cost or finish — it’s whether the dimensions physically work on your truck bed. One wrong measurement leaves you with a box that blocks the cab window, collides with a tonneau cover, or takes up more bed floor than planned. The search narrows quickly once you measure your bed rail and know your clearance needs. Start with five checks before worrying about materials or locks.

What to Measure Before Buying a Side Box

Measure the truck bed rail length first. Northern Tool states that buyers should check pickup bed and storage box measurements for compatibility. The box length must fit the available rail span, leaving clearance for the cab, wheel wells, and any existing bed accessories. Next, check three dimensions on the box:

• Length — the rail span it covers, typically 48–90 inches.
• Depth — how far the box intrudes into the bed, permanently reducing floor width.
• Height — how far the box sits above the rails, from 4 inches up to 5-1/2 inches.

Also confirm the opening height of the lid.

Side-Mount Box Sizes and Compatible Trucks

Side-mount boxes attach to the bed rail and preserve more center floor space than crossover boxes. They suit trucks where you need side access, such as reaching tiedown points or gear against the tailgate. Compatibility is not universal. Listings describe fitment as “most full-size and mid-size pickup truck makes and models” but still require measurement verification.

Look at the smaller and larger extremes side by side. The 64-inch model stores 10.8 cubic feet and fits most full-size trucks without a long-bed requirement. The 90-inch version covers nearly the whole rail span and suits extended or crew cabs with long beds. Choosing a box closer to your measured rail span prevents overhang.

Mounting Side and Lid Hardware: What Matters Most

Confirm whether the box mounts on the driver side, passenger side, or either. Several side-mount boxes are reversible, but others are fixed. Pick the access side you actually use — if you park against a wall, a driver-side box may stay permanently unreachable. Lid hardware matters if you open the box often. Listings commonly include foam-filled lids, paddle or pull latches, gas struts, or self-rising shocks. Gas struts and self-rising shocks keep the lid open hands-free, while paddle latches stay easy to use with work gloves. For mounting on a specific vehicle, follow that box’s fitment instructions. Some models include adjustable legs or pivoting designs for angled or curved rails.

Material, Finish, and Common Mistakes to Avoid

Choose aluminum if you remove the box seasonally or care about payload; choose steel only if you don’t mind the extra pounds. Finish affects corrosion resistance and appearance — powder-coated aluminum survives weather, while textured matte coatings hide scratches.

Buyers commonly make these mistakes:

• Buying by advertised length only, ignoring lid clearance or rail height.
• Forgetting the box extends 16–18 inches into bed space permanently.
• Choosing a box too tall for a cap, cover, or cargo setup.
• Not confirming driver-side, passenger-side, or reversible mounting.
• Overlooking material and finish differences affecting corrosion and weight.

When you’ve narrowed down measurements and access side, the choice comes down to build quality and price. If you plan to run a tonneau cover or bed cap, check the box’s open height against the cover’s clearance before ordering — a box that hits the cover at full open damages the lid over time.