How to Measure Your Truck Bed for a Tonneau Cover (and Why Inches Lie)

Every tonneau cover is built for one truck generation and one bed length, so the first job is knowing exactly which bed you have. That sounds simple until you notice that Ford calls a bed “5.5 ft,” the cover box says “5’7”,” and your tape measure says something else again. This guide explains where to measure, how each truck maker measures, and what else besides length decides which cover part fits.

The bed lengths below come from the truck makers’ own spec sheets and brochures, the same data behind our bed size finder. The cover sizes come from the Amazon listings we checked on November 12, 2026.

Where to measure

1. Close the tailgate. Cover length is set by the closed tailgate, not the bed floor with the tailgate down.
2. Measure along the floor, from the inside face of the front bulkhead (the wall behind the cab) to the inside of the tailgate. Ford, GM and Toyota publish bed length this way: inside length at the floor.
3. Measure in the middle, not over a wheel well or a bed liner lip. A thick drop-in liner can shave a little off.
4. Note your cab style (crew, extended or regular) and the model year. You’ll need both.

Then round to the nearest nominal size listed for your truck. Don’t expect your measurement to match a listing to the tenth of an inch.

Nominal sizes vs real inches

Covers are sold by nominal names that rarely match the truck maker’s wording, and different makers’ inches don’t quite agree either. Some common examples:

The Tundra is a good example of why you shouldn’t chase decimals: Toyota’s 2025 brochure gives 65.6 in for the current CrewMax short bed, while cover listings for that truck still say 66.7 in, the figure Toyota published for the previous generation. Both describe the same nominal 5.5 ft bed, and the cover made for the 2022+ truck is the one that fits it. The Colorado and Canyon figure is our conversion of GMC’s “5.1 ft,” so it could be off by about half an inch.

How each truck maker measures

The bed size finder shows the basis for every truck, because the makers don’t all measure the same way:

• Ford: “inside length (at floor)” for the F-150 and Super Duty; Maverick figures are bed length with the tailgate closed.
• Ram: “length at floor, tailgate closed” for the 2019+ 1500, and simply “bed length” in some newer guides.
• GM: “inside length of box at floor” for the Silverado; GMC’s brochures give rounded feet for some trucks.
• Toyota: “inside bed length.”
• Honda publishes the Ridgeline’s bed length with the tailgate up (64.0 in), and Hyundai the Santa Cruz’s at the floor (52.1 in). Covers for those two are sold by model rather than by length.

Small differences between brands are normal and don’t mean your truck is unusual.

Look up your truck instead

Measuring is a good check, but the fastest route is to look up the maker’s figure:

• 2021+ F-150 SuperCrew short box: bed size finder for the F-150 5.5 ft
• 2019+ Ram 1500 Crew Cab 5’7”: bed size finder for the Ram 1500
• 2019+ Silverado 1500 Crew Cab short bed: bed size finder for the Silverado
• 2024+ Tacoma Double Cab 5 ft: bed size finder for the Tacoma
• 2022+ Tundra CrewMax 5.5 ft: bed size finder for the Tundra

Each result shows the maker’s figure, the nominal size covers use, and the cover listings we’ve verified for that truck and bed.

What changes the part number besides length

Two trucks with the same bed length can need different covers. Check these before you order:

Generation

Covers clamp to the bed rails, bulkhead and tailgate, and those shapes change between generations. Covers for the 2016–2023 Tacoma don’t fit the 2024+ truck; every line we checked for both generations sells separate parts. Many lines sell separate F-150 parts for 2015–2020 and 2021+, though some, like the TruXedo Lo Pro F-150 5’7” listing, cover both.

Factory bed options

• Ram 1500: RamBox side bins and the Multi-Function (split) tailgate each need their own versions. The BAKFlip MX4 Ram 5’7” listing, for example, doesn’t fit the split tailgate.
• Silverado and Sierra: the CarbonPro composite bed needs specific parts, and some covers note MultiPro/MultiFlex tailgate compatibility.
• Tacoma and Tundra: the factory deck rail system and Trail Special Edition storage boxes change fitment.

Your own accessories

Over-the-rail bed liners, aftermarket bed rails and toolboxes can block the clamps. Tyger says owners with over-the-rail liners need to cut small holes for its T3 clamps.

Ram 1500 vs Ram 1500 Classic

The Classic was sold alongside the new truck from 2019 to 2024 and takes different covers. Tyger’s T3 Ram listing, for instance, says it doesn’t fit the 2019–2024 Classic.

Heavy-duty, compact and other midsize trucks

The same rules apply beyond the half-tons. From the makers’ own documents in our finder:

• Ford Super Duty 2023+: 6.75-ft box 81.9 in and 8-ft box 98.1 in, inside length at the floor.
• Ram 2500/3500 2019+: 6’4” box (76.3 in) and 8’ box (98.3 in).
• Nissan Frontier 2022+ Crew Cab: 5 ft (59.5 in) and 6 ft (73.3 in) pickup box cargo length.
• Jeep Gladiator 2020+: 60.3 in with the tailgate closed.
• Ford Maverick 2022+: 54.4 in with the tailgate closed, the shortest bed in our finder apart from the Santa Cruz.

We left out trucks where we couldn’t find a maker figure, including the 2017–2022 Super Duty, the Nissan Titan and GM’s 2500HD/3500HD, rather than guess.

Bed size affects which cover type makes sense

Once you know the length, think about how much of it each cover leaves usable. A retractable’s canister takes roughly 7–14 in at the cab end depending on the brand, which is a bigger share of a 5 ft Tacoma bed than of an 8 ft F-150 bed. A standard tri-fold folds over the front third. Our bed access calculator draws each type to scale for your bed.

Confirm before you buy

1. Find your bed in the bed size finder, or measure floor length with the tailgate closed.
2. Open the cover listing and use its fitment tool (Amazon’s “Confirm fit” or the maker’s vehicle selector) with your year, cab and bed.
3. Read the fitment line for exclusions: RamBox, split tailgate, CarbonPro, deck rails, storage boxes.
4. If you have an over-the-rail liner or bed rails, check the install notes.

When you’ve got the right bed, see our picks for the F-150, Ram 1500, Silverado and Tacoma, or the install guide for what comes next.