How to Measure a Truck Bed for a Tonneau Cover (and Why a 5.5 ft Bed Is Not 66 Inches)

Close the tailgate, hook a steel tape on the bulkhead (the bed wall behind the cab), run it along the floor to the inside face of the tailgate, and round to the nearest inch. That inside floor length, not the "5.5 ft" or "6.5 ft" on the window sticker, is the number that picks your tonneau cover. A Ford F-150 "5.5 ft" bed actually measures 67.1 inches on Ford's own spec sheet, which is why the covers for it are sold as 5'7".

Key Takeaways

• Measure inside the bed with the tailgate closed, from the bulkhead to the inside face of the tailgate, and write the result in inches.
• Marketing names are rounded. Beds sold as "5.5 ft" run from 65.6 in on a 2022 and newer Tundra to 69.9 in on a Silverado 1500, per RealTruck's bed chart.
• Rail length and floor length are usually within about an inch on modern beds. Either works for a cover as long as you say which one you took.
• Cab type does not tell you the bed length, and the same nameplate can change by an inch between generations.
• Liners, RamBox, MultiPro tailgates and Toyota deck rails don't change how long the bed is, but they do change which cover fits.

Why the marketing bed size will get you the wrong cover

Truck makers round bed lengths to a friendly number, and cover makers sell by the real one. Ford calls the F-150's short bed "5.5 ft," but the spec sheet lists 67.1 inches inside, which is 5 ft 7 in. Cover listings call that a 5'7" bed, so a buyer searching for a "5.5 ft" cover often lands on the wrong product. One F-150 Lightning owner asked a forum whether to buy the 5'5" or 5'7" listing, and an installer answered, "It is the 5'7", I have installed many".

The same nominal size lands on different lengths across brands. In the 5.5 ft class, a 2022 and newer Toyota Tundra CrewMax bed is 65.6 in, a Nissan Titan Crew Cab is 67.0 in, an F-150 is 67.1 in, a Ram 1500 is 67.4 in, and a Silverado 1500 "short" box is 69.9 in per RealTruck's bed chart. That's a spread of more than 4 inches under the same label.

The same nameplate can move between generations too. Toyota listed the Tundra 6.5 ft bed at 78.7 in through 2021 and at 77.6 in from 2022 on. The older figure comes from a Toyota filing we could only read in part, so confirm it on your truck. A 2024 Tundra owner confirmed 77.6 with a tape while most vendors still listed 78.7, and the 78.7 cover he bought did fit, but an inch matters more with some cover styles than others. That's why every page in our fitment guide index asks for the measured number, not the badge.

What you need

You can do this alone, but a second set of hands makes it faster.

• A steel tape measure at least 12 ft long, so an 8 ft bed doesn't run you off the end of the blade.
• A helper to hold the tape hook against the bulkhead, or a spring clamp to do the same job.
• Your window sticker, build sheet or a VIN decode from the manufacturer's site, so you can compare your tape number to the factory figure.
• Your phone, to write down the numbers and photograph the tape where it meets the tailgate.

How to measure your truck bed in 3 steps

Step 1: Close the tailgate and clear the bed

Latch the tailgate and empty the bed. That is the one condition every measuring guide agrees on. Guides split on tailgate up or down, but the number comes out the same as long as the tape stops at the plane of the tailgate's inside face. Closing it removes the temptation to run the tape out to the tailgate lip.

Jeep shows why that matters by publishing both figures for the Gladiator: 60.3 in with the tailgate closed and 81.3 in with it open. Pull out toolboxes, loose mats and anything leaning against the bulkhead before you start.

Step 2: Measure length from the bulkhead to the inside face of the tailgate

This gives you the inside floor length in inches, which is the number our fitment charts use. Hook the tape on the bed floor where it meets the bulkhead, run it straight back along the floor, and read it where it touches the inside face of the closed tailgate. Take it once down the center and once near a side wall. If the two readings disagree by more than a hair, the tape wasn't square. RealTruck's guide says you should be accurate to within 1/4 in.

If you have a drop-in liner, measure inside the liner, because that's the opening the cover has to close over. For a second check, repeat the measurement along the top of the bed rail, bulkhead to the inside edge of the tailgate top. On modern beds the rail and floor readings we've compared land within about an inch of each other. RealTruck measures at the rail, while most other guides, including LINE-X and OnAllCylinders, measure at the floor with the tailgate closed. Either is fine as long as you tell the seller which one you took.

Step 3: Measure width and write both numbers down in inches

Measure width from the inside of one bed rail to the inside of the other at the bulkhead end, then again at the tailgate end. Round the length to the nearest inch and write it as "67 in," not "5.5 ft."

Don't panic if you're a little off the chart. Peragon's guide notes that about an inch of variance from the published spec is normal on a real truck. Tape angle, liner thickness and where the tailgate seal sits account for most of it.

Truck bed length chart by make

All figures are inside length at the floor with the tailgate closed, in inches, taken from manufacturer spec sheets unless marked otherwise. The years shown are the generation each spec sheet covers. Older generations can differ, so treat the chart as a check on your tape, not a replacement for it.

Ford

The F-150 figures come from Ford's 2018 technical specs; RealTruck's 2026 chart lists the same numbers for the current model.

Chevrolet and GMC

GM's own spec pages wouldn't load when we checked, so these figures are per RealTruck's bed chart, cross-checked against dealer pages.

Ram

Ram is the one brand where the 1500 and the HD share a bed length in the mid size. Watch for RamBox, covered below.

Toyota

Toyota is the brand where generation matters most. The 2022 redesign shortened every Tundra bed by about an inch, and the 2024 Tacoma moved a couple of tenths.

Nissan, Jeep and Honda

Short vs standard vs long: how to tell which you have

Cab type doesn't tell you bed length, and neither does the trim level. Crew cabs most often ship with the shortest bed, but plenty are ordered with the mid-length bed. A 2006 Tundra Double Cab owner found that every site still asked him to pick between two bed lengths after he chose his cab, and he settled it with a tape.

If you'd rather decode than measure, the window sticker or build sheet lists the box length in the same rounded marketing terms as the chart. Match that name to your make's row and you have the inch figure to expect. Then put a tape on it anyway, because the chart tells you what left the factory, not what a previous owner may have added.

Once you have your inch number, the class is obvious from the chart above. Anything from the low 60s to just under 70 is a short bed; the low 70s to low 80s is a standard bed; the high 90s is a long bed. The gaps between classes are wide enough that you can't land in between by accident, but the gaps within a class are small enough that you can't skip the tape.

Things on your truck that change which cover fits

None of these change how long your bed is. They change what the cover has to clamp to, seal against or clear, so mention them when you order.

Bed liners

Under-rail drop-ins and spray-in liners sit below the clamp surface and rarely interfere with a tonneau cover. Over-the-rail drop-ins wrap the top of the rail, and RealTruck's compatibility guide warns that "some trimming at the clamp locations may be required" with those. LINE-X adds that a spray liner can leave an uneven rail edge, which matters for covers that seal on the rail.

Measure inside the liner, not the bare bed. OnAllCylinders recommends deducting the thickness of a thick drop-in or spray liner, rail cap or tailgate cover from the bare measurement, which gets you to the same place.

RamBox

RamBox trucks need a RamBox-specific cover. The storage bins live inside the bed rails, so the rail tops are wider and the bin lids have to open under the cover. Ram's own accessory listing for its hard tri-fold says it fits trucks with the 5'7" bed and RamBox and is "Not compatible with non-RamBox beds". Owners on 5thGenRams trade notes on which aftermarket covers clear the bins for the same reason.

GMC MultiPro and Chevy Multi-Flex tailgates

The six-function tailgate on 2019 and newer GM 1500s and 2020 and newer HDs has an inner gate, and the cover has to seal against that inner panel. That gap is a known water and dust path. RealTruck's MultiPro guide lists compatible examples including the BAKFlip MX4, RetraxPRO XR and UnderCover Elite LX, and the safe rule is to buy only a cover that names MultiPro or Multi-Flex on its fitment.

Ford Pro Power Onboard

Pro Power Onboard on 2021 and newer F-150s, the Lightning and Super Duty puts an outlet panel inside the bed. Ford's support page lists up to four 120V/20A outlets on the 2.0 kW system and up to six plus a 240V outlet on the 7.2 kW system. The panel doesn't change bed length, but it needs to stay reachable with the cover installed, so tell us if you have it.

Toyota deck rails

Tacomas since 2005 use a lipless bed rail with an aluminum deck rail channel and sliding cleats, and higher Tundra grades get the same deck rail system. Toyota's product information shows it standard on every 2016 Tacoma grade and standard on the 2025 Tundra SR5 and up. RealTruck's deck rail guide explains that hard-folding covers use drop brackets and keep full rail use, while retractables mount on hanger brackets and slightly limit cleat travel. The factory tall tie-downs that sit above the rail interfere with many covers and usually have to come off.

Rail caps, tie-downs, bed extenders and tailgate steps

Thick aftermarket rail caps add height at the clamp surface, so note them. Factory tie-down rails and stake pockets are fine as long as the cover rails don't overlap the pocket, per RealTruck's compatibility guide. Ford BoxLink cleats sit on the bed wall and normally clear.

Bed extenders are the one to watch. RealTruck notes that "Hinged covers may not be compatible with bed extenders" because the cover can't latch closed over them, so the extender has to flip in or come off. Tailgate steps and cameras don't change the opening, but LINE-X flags that "Steps, cameras, and easy-lift systems may cause interference" at the tailgate edge.

The 6 measuring mistakes we see most

1. Trusting the marketing name. The same "5.5 ft" label covers 65.6 in on a Tundra to 69.9 in on a Silverado, per RealTruck's bed chart. Use the inch figure.
2. Measuring from the outside of the tailgate. RealTruck calls this the most frequent error. It adds several inches and puts you in the next bed class.
3. Measuring to the open tailgate lip. The Gladiator's 60.3 in closed becomes 81.3 in open. Close the gate.
4. Ordering by cab type. Crew cab doesn't mean short bed. Measure or read the window sticker.
5. Ignoring what's already in the bed. Over-rail liners, thick rail caps and cargo systems change the opening and the clamp surface. Measure inside them and tell the seller.
6. Ordering a 1500 cover for an HD. A Silverado 1500 standard box is 79.4 in and the 2500HD standard box is 82.3 in, per RealTruck's bed chart. Ram is the exception, with both the 1500 and HD 6 ft 4 in beds at 76.3 in.

How to match your measurement to a cover

Take your inch figure, not the marketing name, to the fitment page for your truck in the fitment guide index. The charts at Truck Bed Covers use inside floor length, measured from the bulkhead to the inside face of the closed tailgate and rounded to the nearest inch, and we confirm fit with you before anything ships. If your number lands between two rows, or your truck has RamBox, MultiPro, deck rails or an over-rail liner, send us the length, the width and a photo of the tape at the tailgate and we'll match it by hand.

Once the cover is on the way, the installation guide covers clamp placement and the rail-seal check, which is where a measurement that was an inch off shows up first.

Frequently asked questions

Do you measure a truck bed with the tailgate open or closed?

Closed. The measurement is the same either way if you stop the tape at the plane of the tailgate's inside face, but with the gate down it's easy to run out to the lip. Jeep publishes both numbers for the Gladiator, 60.3 in closed and 81.3 in open, which shows how far off you can be.

How do I know if I have a 5.5 ft or 6.5 ft truck bed?

Measure from the bulkhead to the inside face of the closed tailgate. Anything from the low 60s to just under 70 inches is the short bed, and the mid to high 70s is the mid-length bed. Your window sticker or build sheet also lists the box length, and the chart above converts that name to inches for your make.

Should I measure at the bed floor or the bed rails?

Our charts use the floor, but on modern beds the two are usually within about an inch of each other. RealTruck measures at the rail while LINE-X, OnAllCylinders and most other guides measure at the floor. Take both if you want a second check, and say which one you're quoting when you order.

How accurate do truck bed measurements need to be?

RealTruck recommends accuracy to within 1/4 in, and that's a good target for the tape. In practice, Peragon notes about an inch of variance from the published spec is normal on a real truck. Round to the nearest inch, and if you're more than an inch off the chart, measure again and check for a liner or rail cap.

Why doesn't my truck bed match the advertised size?

The advertised size is rounded and the tape isn't. Ford's "5.5 ft" F-150 bed is 67.1 in, Toyota's "5.5 ft" Tundra is 65.6 in, and Chevy's "short" box is 69.9 in per RealTruck's bed chart. Liners, rail caps and a tape run to the outside of the tailgate account for the rest.

Can I use manufacturer specs instead of measuring?

Use them as the check, not the answer. Spec sheets are accurate for the generation they cover, but they don't know about your drop-in liner, aftermarket rail caps or a replacement tailgate. The 2024 Tundra owner who found vendors listing the old 78.7 in figure for a 77.6 in bed is the reason we still ask for a tape number.

Do bed measurements change between model years?

Yes, mainly at generation changes. The Tundra 6.5 ft bed went from 78.7 in through 2021 to 77.6 in for 2022 and newer, and the Tacoma 6 ft bed moved from 73.7 in to 73.5 in for 2024, per RealTruck's bed chart. Within a generation the bed is usually unchanged, but confirm your model year on the fitment page for your truck.

Sources

• Ford 2018 F-150 Technical Specifications
• Ford 2025 Super Duty Technical Specifications
• Ram 2025 Ram 1500 Specifications
• Ram 2019 Ram 1500 Classic Specifications
• Ram 2024 Ram 2500/3500 HD Specifications
• Toyota 2025 Tundra Product Information (hosted by Automoblog)
• Toyota 2014 to 2021 Tundra figures (NHTSA filing)
• Toyota 2016 Tacoma Product Information (hosted by IH8MUD)
• Nissan 2019 Titan Specifications
• Jeep 2023 Gladiator Specifications
• Ford Pro Power Onboard support page
• RealTruck bed length chart (GM and 2024+ Tacoma figures)