GMC Sierra 1500 Truck Bed Dimensions for Camping: All Three Beds, One Honest Chart

Two hundred miles from the nearest parts store, the difference between stretching out flat in a Sierra bed and folding up in it comes down to a box someone checked at the dealer: which of the three beds is bolted to the truck. GMC builds the Sierra 1500 with a 5'8", a 6'6" and an 8' bed, and for sleeping they are three genuinely different platforms - not trim badges. Pick the wrong number off a generic chart and you're planning around the wrong truck.

On my rig, the number that decides whether I sleep flat and the number that decides whether my drawers and water fit are the same number - floor length - so that's where this page starts. The good news is the Sierra makes the rest easy: the floor is flat, and the width and depth don't change between beds. Only length moves. That means you can read all three beds off one honest chart and match it to your own height.

Here's what this page does: lay out all three beds with real floor lengths, the width between the wheel wells, and the depth; tell you which bed fits a six-footer flat; and work the short-bed rescue - the diagonal and the MultiPro tailgate - for the popular Crew Cab short bed. If you also want the accessory and setup side, our GMC Sierra camping accessories guide covers the gear; this one is the geometry.

Start with the floor lengths, because that's what decides a bed. Measured figures put the Sierra 1500's short bed at about 69.9 inches of floor, the standard bed at about 79.4 inches, and the long bed at about 98.2 inches. Those mirror the measured drawings and the dealer spec sheets, which agree closely.

• 5'8" = ~70 in floor: the short bed - the volume seller, and short for sleeping flat.
• 6'6" = ~79 in floor: the camping sweet spot - long enough for most adults to stretch out flat.
• 8'0" = ~98 in floor: the long bed - room to spare, plus gear at your feet.

Note the nominal names round hard: the "5'8" bed is really closer to 5'10" of floor, and the "8-foot" bed measures about 98 inches, not a clean 96. Use the measured inches, not the marketing feet. Read the floor length as your straight sleeping length and hold it against your own height - a six-footer is 72 inches, and that's the line the short bed sits just under.

The width that matters for anyone lying on the floor is the pinch between the wheel wells, and on the Sierra it's about 50.6 inches - the same across all three bed lengths. That's the real usable width on the floor, not the wider figure up at the bed rails.

Fifty and a half inches is a little over four feet - room for one wide pad, or two narrow ones side by side. A queen mattress is 60 inches, so it does not fit flat between the wells. That's the single most common full-size-truck camping-bed mistake.

What that means for your setup:

• One sleeper: easy - a 20-to-25-inch pad has room to spare on the floor.
• Two sleepers: two twin-width pads fit between the wells; skip the queen or build up over them.
• Over-the-wells platform: a deck level with the wheel-well tops reclaims the full 71-inch rail width above them and turns the wells into storage.

Down at floor level you have that constant 50.6 inches the whole length of the bed, which is why two twin-width pads is the honest two-person answer without building a platform.

Depth is the full-size Sierra's quiet advantage. The bed is about 22.4 inches deep across all three lengths, and the floor is flat - so a sleeper lies well below the top of the bed sides, with the tailgate and walls acting like a low windbreak around you.

• 22.4 in of depth: deep enough that you're tucked down out of the wind, not perched on top of the truck.
• Flat floor: no hump or ribs to fight - a pad or a platform sits clean.
• The trade: the depth is comfort, but it also means climbing in over a tall side - fine for most people, worth knowing if mobility matters.

That 22.4-inch depth is a real edge over a mid-size or a unibody truck, which run several inches shallower and shelter you less. Because the depth is constant across all three beds, a platform height you calculate once carries over even if you switch bed lengths later. Build the deck an inch or two below the rail and you keep the low-wall shelter the depth gives you while still leaving headroom under a canopy - lose that and you trade the truck's best sleeping feature for a little under-bed storage you could have gotten over the wells instead.

Bed length isn't a free choice on the Sierra - GMC pairs it with cab size, so your cab tells you which beds were possible. Across the sources that agree, the pairings run: Crew Cab with the 5'8" or 6'6" bed; Double Cab with the 6'6" bed; and Regular Cab with the 8' bed.

• Crew Cab (the volume seller): most Sierras on the road are Crew Cabs, and they most often wear the 5'8" short bed - the one that makes you work to sleep flat.
• Double Cab: the 6'6" bed - a good camping length with a usable back seat.
• Regular Cab: the 8' long bed - the best bed length, the least cab room.

The practical read: if you bought the popular Crew Cab short bed, the next two sections are written for you. And because these pairings shift a little by model year and trim, confirm your own truck's bed rather than trusting the badge - a couple of inches decides whether you clear the six-footer line.

Here's the honest math for a tall sleeper. A six-footer is 72 inches. The 6'6" bed's 79-inch floor swallows that with room to spare, and the 8' bed obviously does. The 5'8" bed's roughly 70-inch floor does not - you're a couple of inches short of lying flat straight with the tailgate up.

If you're on the Crew Cab short bed and taller than about 5-foot-9, you have three honest options: sleep on the diagonal, drop the MultiPro tailgate, or build over the wheel wells. Pretending 70 inches fits a six-footer straight is how you wake up braced against the cab.

None of those are bad options - they're choices you make on purpose instead of discovering at midnight. The good news for the Sierra short bed is that the margin is small: you're two or three inches short straight, which the diagonal erases completely. Every inch of pad you add under you effectively steals a little from the length, so a borderline sleeper should run a low-profile pad rather than a lofty air mattress. The next two sections cover the diagonal and the tailgate, which are how most short-bed owners actually sleep.

The quiet win of the Sierra short bed is that you don't have to sleep parallel to the sides. The diagonal of a 50.6-by-70-inch floor is longer than either edge - about 86 inches - so a six-footer lies flat corner to corner with the tailgate closed and the weather locked out.

Diagonal sleeping keeps the tailgate shut and the wind out, and it costs nothing but the willingness to sleep at an angle. On a full-size short bed the diagonal is so generous - about 86 inches - that even a tall camper clears it easily. Try it before you commit to a tailgate-down build.

The limits are the same as any bed: only one person fits on the diagonal, and the wheel wells eat the corners, so measure the clear diagonal on the floor, not the rail. Lay it from the bulkhead corner on one side to the tailgate corner on the other, and check the far corner for tie-down cleats or a bedliner lip the pad has to clear. For a solo camper on a Crew Cab short bed, diagonal-tailgate-up is the simplest flat, sheltered night the truck offers - and on the Sierra, with its deep 22.4-inch walls, it's a genuinely cozy one.

Dropping the tailgate is the classic short-bed fix, and the Sierra's MultiPro tailgate makes it a little nicer than most - it's a six-function gate with an inner load-stop and a fold-out step. But here's the gap I won't paper over: neither GMC nor the aggregators cleanly publish how many inches the open gate adds to your sleeping length.

• What it buys: a pickup tailgate panel is roughly 20 inches deep, so laid flat it adds about that much length - enough to turn the short bed into a flat run for a tall sleeper.
• The catch: the gate sits a touch lower than the floor and isn't perfectly load-flat, so bridge the seam with a pad or a board so your hips don't drop into the lip.
• Weather: an open gate needs a canopy or topper over it, or your feet are outside in the rain.

Because the exact added length isn't an official figure, measure your own gate rather than trusting a chart - a two-minute check that decides whether tailgate-down is worth it for you. The MultiPro's inner gate can also stand up as a load-stop, which is handy for keeping a pad or gear from sliding out the open end while you set up.

One thing worth saying plainly, because it saves cross-shoppers a lot of confusion: the GMC Sierra 1500 and the Chevrolet Silverado 1500 are the same truck underneath. They ride on GM's full-size platform and share the bed - the same three lengths, the same 50.6 inches between the wheel wells, the same 22.4-inch depth, the same flat floor.

For a camper that means a sleeping setup, a pad size, or an over-the-wells platform built for one fits the other. The differences are trim, tailgate features and available options - the Sierra's MultiPro gate versus the Silverado's Multi-Flex, the badges, the interiors - not the bed geometry you sleep on. If you're weighing the two, our Chevy Silverado 1500 bed breakdown runs the same numbers from the Chevy side, and the setup is interchangeable.

The reason I flag it: people burn time hunting for a separate "Sierra bed size" when the honest answer is that the Silverado's numbers are the Sierra's numbers. Measure once, and it's true for both.

A truck bed's weakness against an SUV is that it's open to the sky, so on any of the three Sierra beds, weather protection is part of the build. The good news is the deep 22.4-inch sides do a lot of the low-wind work for you - a cover only has to close the gap from the rail up.

• Level the floor: a Klymit Static V pad turns the hard, flat bed floor into a sleepable surface and packs down small - the base layer for any of the three beds.
• Keep the rain off: a Rightline Gear tailgate canopy clamps over the open bed to shed rain and dew without the cost of a topper - ideal for a tailgate-down short-bed setup.
• The upgrade path: a hard or soft topper is the all-weather answer if you camp often, but start with a pad and a canopy and see how much you actually need.

Order of operations, from a lot of nights out: level the floor, then cover it. Guy-line a clamp-on canopy off a stake pocket so a gust can't lift it, and if you're sleeping tailgate-down, size the canopy to overhang the open end - that's where the weather gets at your feet.

Bed charts are a starting point, not a spec for your truck. Before you buy a pad, a topper or build a platform, take these four numbers in your own Sierra bed - ten minutes that saves a wrong purchase.

• Floor length: bulkhead to closed tailgate - your straight sleeping length.
• Wheel-well width: the pinch between the wells at its narrowest - the real two-pad ceiling.
• Diagonal: corner to corner on the floor, clear of the wells - your tailgate-up flat option on the short bed.
• Tailgate-down length: floor plus the open MultiPro gate - because the added length isn't officially published.

Take the wheel-well width at the narrowest point - usually the front face of the well, not the middle. And if you run a spray-in or drop-in bedliner, measure over the liner and knock a bit off both the 50.6 and the floor length, because a liner quietly steals a fraction of an inch everywhere it coats - enough to matter when you're already a couple of inches short on the short bed. Write the numbers down and take each twice.

The GMC Sierra 1500 makes a genuinely good truck-bed camper, with one thing to get right up front: which bed you have. The 6'6" and 8' beds fit a six-footer flat with the tailgate up; the popular Crew Cab's 5'8" bed sits a couple of inches short straight - which the roughly 86-inch diagonal erases, or the MultiPro tailgate solves with another 20 inches. All three share 50.6 inches between the wheel wells - too narrow for a flat queen - and a deep, flat 22.4-inch floor that shelters you well.

Know your bed length, measure the floor and the diagonal, level it with a pad, cover it with a canopy or topper, and the Sierra sleeps one easily - two with twin pads or an over-the-wells platform. And whatever you build fits a Silverado, too.

Buy the bed length to your height if you can. If you're cross-shopping, our Ford F-150 and Ram 1500 bed breakdowns weigh the same length-versus-width question across the full-size class.