Calculators

Four pieces of arithmetic every trailer owner ends up doing on a napkin. Each one shows its formula and its assumptions under the tool, so you can disagree with a number and change it.

• Tongue weight and payload calculator

  Enter the loaded trailer weight and the truck's door-sticker payload. Get the 10 to 15 percent tongue-weight target, what a measured tongue weight means, and how much payload is left after people, hitch, and cargo.

• Boondocking battery runtime calculator

  Tick the loads you actually run, set hours per day, pick chemistry and capacity and the overnight temperature. Get amp-hours per day, usable capacity, days of runtime, and the solar wattage needed to break even.

• Propane runtime calculator

  Furnace rating and outside temperature drive almost everything. Add the fridge, water heater, and stove and see days remaining on 20, 30, or 40 lb cylinders.

• Winterizing antifreeze and sanitizing calculator

  How many gallons of RV antifreeze your layout needs (with or without a blow-out first), and how much bleach to sanitize the fresh tank in spring.