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The simplest way to determine trailer tongue weight is with a tongue scale; a scale designed so you can place the trailer’s tongue on it. You can then read the weight directly from the scale. In a pinch, though, whether you use a static trailer hitch or a weight-distributing hitch, you can use a common household appliance and some simple math to work out the optimum trailer tongue weight.
Items you will need
One 2-by-4, five feet long
Avoid a Tongue Weight Too Heavy or Too Light
Take your towing vehicle and trailer to a commercial truck scale. Disconnect the trailer and weigh your tow vehicle. Reconnect the trailer and weigh both your trailer and your vehicle.
Subtract the weight of your towing vehicle from the combined weight. This is your trailer weight. Look at the label inside the driver's side door frame and locate the GVWR, the gross vehicle weight rating
Compare the GVWR to the combined weight of your vehicle and trailer to ensure your vehicle can safely manage the combined weight.
Calculate your ideal tongue weight by multiplying the trailer weight by 0.10. The result is the minimum safe tongue weight. Multiply the trailer weight by by 0.15. This is the maximum safe tongue weight.
One Bathroom Scale, Two Methods
Place a cinder block flat on a bit of level ground. Lay a second cinder block atop the first. The blocks should be laying on their sides, so the holes through the blocks are on the sides of both blocks. Place your bathroom scale on top of the stack of blocks.
Move your trailer tongue onto the scale. Read the tongue weight directly from the scale. Watch the scale as you settle the tongue onto it. If the scale advances to its limit, remove the tongue from the scale and place the scale directly on the ground.
Place a brick of the same thickness as the scale three or four feet from and parallel to the scale. Place a length of pipe lengthwise on the scale and a second length of pipe lengthwise on the brick. Place a five-foot-long 2-by-4 atop the pipe sections on the brick and the scale. Place the tongue of the trailer on the 2-by-4. Use a measuring tape to measure the distance to the pipe atop the scale and the distance to the pipe on top of the brick.
Read the scale. Multiply the result by the total of the distance between the tongue and the brick and the distance between the tongue and the scale. If the distance between the scale and the tongue is three feet and the tongue and the brick, one foot, multiply by four. The result is the tongue weight. If the distance between the tongue and the brick is 1.5 feet and the distance between the tongue and the scale two feet, multiply the scale’s reading by 3.5 to determine the tongue weight.
Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.