Roof rack and tent calculator
Will the roof carry it, driving and camped? What does it cost at the pump? What does it do to the truck's balance? Pick your truck, then add the rack, the tent and what rides on them one step at a time. The page checks each against the makers' ratings and your owner's manual as you go.
How to use this 3 steps
- Pick your truckIts roof limit, size and NHTSA stability figure fill in from the owner’s manual and the spec sheet.
- Add things one at a timeA rack, then a tent, then roof accessories like a box or an awning, then the gear you strap on. Each one joins the weight, the drag and the balance as you add it, and you can stop after any step.
- Read the verdictIt names the check that’s closest to its limit and what to take off to fix it, then what the setup costs at 65 and what it does to the truck’s balance.
You can skip the maker-filled figures inside each step, and the Fuel and Lift folds under your truck. Picking a product or a truck fills them in. Open them if yours isn’t listed, you run fewer crossbars, or you want your own mpg in the fuel line.
Pick your truck, then add a rack.
The weight ledger
Where these numbers come from Ratings, roof figures, rules applied
Ratings are the makers' and the roof limit is Toyota's, Ford's or whoever built the truck. How a rack spreads its load into the roof structure is between you, the rack maker and your installer. Use at your own risk.
At the pump
Highway, estimateHow this was worked out Drag areas and shape factors
Estimate. Drag from a roof load depends on the shape, the gap under it and how the air leaves your particular roof, and real mileage on how and where you drive. Fill up twice with it on and twice with it off to know yours. Use at your own risk.
Balance
How this was worked out Track, weights, heights
The static stability factor is a geometry number, not a promise. Soft ground, a rut, momentum and a side-hill all tip a truck long before the static angle. Use at your own risk.
Links go to the makers. Check the fitment page for your exact year and roof before you order.
How the numbers work
Why three weight checks?
The rack has a dynamic rating for what it carries while you drive, and a static rating for what it holds parked. The truck has its own roof limit in the owner's manual. The page runs all three and the one closest to its limit is the one that matters. Driving, the tent and the gear count against the rack; the rack, tent and gear together count against the roof. Parked, the people in the tent count too, against the static rating.
Is the rating for the whole rack or per mounting point?
The whole rack, always. Thule, Yakima and Rhino-Rack all state their figures for the complete carrier, and the ISO 11154 and Australian AS 1235 tests they cite load a finished rack as a unit: static pulls, vibration, a lane change, a brake test and a sled crash at 8 to 12 g. No standard gives a per-foot number. The one maker that does is Mercedes, whose G-Class manual allows 150 kg on at least three pairs of feet, 50 kg a pair. Yakima's Australian arm publishes its arithmetic: static is three times dynamic, off-road is two thirds of on-road (half for clamp-on mounts), and the lowest figure in the chain, roof, rack, mount or accessory, governs.
My tent is over the factory roof limit. Is everyone's?
Nearly. Most owner's manuals put the roof at 100 to 220 lb, and that figure is written for the factory rails and crossbars carrying a load while the truck is driven. A hard-shell tent on an aftermarket rack is often past it before any gear goes up. Rack makers rate their racks far higher because the rack spreads the load into more of the roof structure, or into the door frames or the body. The page shows you both numbers so you know what you're deciding; it can't tell you how your roof skin and headliner will like it ten years on.
Pavement or off-road rating?
Dynamic ratings assume pavement. Washboard and rock multiply the load on the mounts several times over, so Rhino-Rack, Yakima and a few others publish a separate off-road figure. Rhino-Rack divides the on-road figure by 1.5; Yakima takes a third off, or half for clamp-on mounts. If your rack's maker publishes none, the page applies the same divide-by-1.5 rule when you switch to off-road and says so.
How is the fuel cost worked out?
Air drag is half a 4x4's fuel at 65 mph and grows with the square of speed. The truck's own drag is its drag coefficient times its frontal area, from a published figure where there is one, else a class default. A tent adds its closed height times its width above the roofline, times a shape factor: a wedge nosing into the wind is about 0.35, a clamshell 0.45, a hard pop-up box 0.5, a soft fold-out in its PVC cover 0.7, a bare platform about 0.9 of its small silhouette. The band around each is wide, so the page shows a range. Owner fill-up tests with hard-shell tents cluster around 1 to 3 mpg on a midsize SUV, which is where the model lands.
What is a static stability factor?
Half the track width divided by the height of the center of gravity. NHTSA publishes it for every rated truck, so it gives us the stock CG height without a tilt table. A suspension lift raises almost everything on the truck by the lift; taller tires raise all of it by half the diameter gain; weight on the roof pulls the CG up in proportion to how much it is and how high it sits. The new SSF comes out of the new CG height, and NHTSA's own curve turns it into a rollover-risk band. The static tip angle, the side slope at which gravity alone tips a parked truck, is the arctangent of the SSF, and the real limit on a trail is far lower.
What about cargo boxes, awnings and the rest?
A cargo box counts like a tent: its width times its closed height above the rack, with a lower shape factor for the tapered ones (about 0.38 for a Thule Motion or Yakima SkyBox against 0.5 for a square box). An awning hangs outboard of the rack, so only its closed case meets the wind, depth times height. Accessories go by how they mount: a fuel can or a case standing up shows its full face, traction boards on edge show their thickness, a table or a Hi-Lift lying along the rack shows almost nothing. A light bar tucked behind a fairing or under a tent’s nose is counted at half. Every item adds its weight to the rack and roof checks and moves the center of gravity by where it sits.
Where do the rack and tent figures come from?
The makers' own product pages and spec sheets, with the maker's dynamic rating as published. Roof limits come from owner's manuals, SSF from NHTSA, and the rest of the truck's figures from factory spec sheets, each one marked unconfirmed until a factory source backs it. Every figure on the page can be edited to match what's really on your truck.
Use at your own risk. These calculators are here to help you plan and to inform your decisions, not to sign off on a build. Many numbers are estimates worked out from factory figures, and some factory figures are not yet confirmed. Check every number against your own truck, its manuals and a qualified shop before you buy parts, cut, weld, lift, regear or drive on it. Long Range Desert Tools is not liable for anything you do based on these calculators or their results. The full terms are in our policies.