Work out your rig’s real travel height, add a safety margin, and compare it with a posted bridge, tunnel or overpass clearance in feet or meters. This is a calculator, not navigation: posted signs and your own measurement always come first.
Park on level ground with the tires at their normal pressure and the rig loaded the way you travel. Find the highest point: usually the air conditioner shroud, but check roof vents, satellite domes, antennas, solar panels, ladders and anything on a roof rack. Lay a straight board or level across that highest point so it sticks out past the edge of the roof, and measure straight down from the underside of the board to the ground. Write the number down, put it on a label near the driver’s seat, and measure again whenever you add something to the roof.
The height in your owner’s manual or on the brochure is a starting point, not a measurement: it rarely includes accessories added later, and suspension, tires and load change it.
Posted clearances are not exact. Roads get repaved and lose a few inches under a bridge, snow and ice pile up in winter, and signs can be rounded, old or missing. Your own height changes too: tires, air suspension and a heavy load all make a difference, and a bump or dip just before a bridge can lift the roof. Many RV drivers keep at least 6 to 12 inches between their measured height and any clearance they will drive under; this checker starts at 12 inches. If a clearance is inside your margin, treat it as too low.
U.S. signs show feet and inches (for example 12′6″). Signs in Canada and on some U.S. routes show meters. This checker converts a posted meter value to feet and inches by rounding down, and converts your height by rounding up, so any rounding works against you, not for you.
On an arched structure the posted clearance may apply only to part of the lane, and the edges are lower. Stay centered where the sign tells you to, and remember that wider rigs may not fit even when the center height is enough.
Some low structures are not posted, especially on rural roads, private property and older overpasses. Plan routes on roads meant for larger vehicles where you can.
In the WhimTrav app you enter your rig’s height, width, length and weight once, and routes are planned around the restrictions in its routing data, with warnings when a known low clearance is near. No routing data is complete, so the app is a second pair of eyes — the signs, and your judgment, still decide. More on planning safe routes in our route safety guide and how to avoid low bridges.
