Adding a trailer changes far more than the weight on the scale. Braking distances grow, especially if the trailer’s own brakes are weak or missing, and climbing a long grade can take two to three times the power of cruising on the flat.

Gearing and tire size decide where the engine runs at highway speed. Taller tires lower the effective axle ratio, which cuts pulling power and throws the speedometer off.

Wind resistance rises with the square of speed, so a tall trailer can halve your range per tank. Plan fuel stops and drive time with towing numbers, not the figures you get driving solo.

Which performance calculator do I need?

For safety margins, the stopping distance calculator compares braking with and without working trailer brakes, and the towing horsepower calculator shows how much power a grade demands at your speed. The trailer drag calculator explains why highway speed costs so much fuel with a tall trailer.

For gearing, the engine RPM calculator shows where the engine runs at a given speed, the tire size calculator compares sizes and speedometer error, and the effective gear ratio calculator shows how bigger tires change pulling power. For planning, the range and travel time calculators give realistic towing numbers for fuel stops and drive time.

Speed is the biggest lever

Almost every number on these pages gets worse with speed. Braking distance grows with the square of speed, air drag with its square and the power to overcome drag with its cube. Slowing from 70 to 60 mph shortens stopping distance noticeably, cuts drag power by more than a third and often extends range per tank enough to skip a fuel stop.

Related guides

Trailer Brakes and Brake Controllers Explained: Brake types, controllers and how to set the gain.
Trailer Tires Explained: ST vs LT, Load Range, Pressure and Age: Read the sidewall, set the pressure and know when to replace.
Towing in the Mountains: Climbing, Descending and Heat: Gears, temperatures and brakes on long grades.

All results are estimates. Always confirm ratings in your owner’s manual, on the door-jamb label and on the trailer’s VIN plate.