RV calculators
Size batteries, solar, wire, hitches and tanks before you spend the money. Free, no sign-up, and they run in your browser.
- 25 calculators
- 6 systems
- Updated
Electrical
Shore power, batteries, solar and everything that draws from them.
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RV Battery Calculator
Tick your appliances and hours to get daily watt-hours, the amp-hour bank that covers it in lithium or AGM, the inverter that clears your biggest load, and the batteries that make that bank.
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RV Amp Draw Calculator
Estimate running amps and startup loads on 30A or 50A RV service, then download your appliance amp-draw card as a Letter or A4 PDF.
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RV Battery Charge Time Calculator
Work out how long your bank takes to charge from your own numbers — bulk and absorption separately, and whether your converter or your battery is the thing setting the pace.
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RV Battery State of Charge Calculator
Interpret a 12V battery reading, see an illustrative load correction and learn when a rested-voltage reference can support a rough state-of-charge estimate.
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12V Wire Size Calculator
Size DC cable for an inverter, a DC-DC charger or any 12V circuit. Shows the gauge voltage drop needs, the gauge ampacity needs, which one binds — and whether it will fit your device's terminals.
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RV Solar Size Calculator
Size RV solar for your camping month and roof space using NASA's monthly sun data. Download a Letter/A4 peak-sun-hours chart for 14 U.S. destinations.
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Solar Panel Tilt Calculator
On NASA's data, tilting RV panels adds 37% to 93% in December from Orlando to Seattle, and loses 10% to 16% in June. Work it out for your panels and month.
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RV Extension Cord Calculator
Work out the voltage your RV actually gets through its shore cord and an extension — counting the round trip, the coiled slack, and the drop a portable EMS at the pedestal never sees.
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Solar Fuse Calculator
Size every fuse in an RV solar system from your own panels: the strings, the array to the controller, and the controller to the battery, by the makers' figures.
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Generator Size Calculator
Size an RV generator from Dometic's guideline, altitude and heat. Compare peak watts with running output, and see where manufacturer derating data is missing.
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Charge Controller Size Calculator
Size an MPPT controller on the two figures that can damage it — cold open-circuit voltage and short-circuit current — not on watts, which Victron says it simply limits.
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Water
Fresh, grey and black — filtration, pressure, pumps and sanitation.
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RV Hot Water Calculator
Work out how many minutes of hot shower your RV water heater gives, from your own shower head, temperatures and heat source — and which free change buys the most time before you spend anything.
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RV Water Pump Calculator
Find the RV water pump that holds pressure with your shower and faucets open at once — read off each maker's own flow curve, not the GPM on the box.
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RV Water Tank Calculator
Work out how long your fresh, grey and black tanks last on your own usage — and which of the three actually ends the trip. It is almost never the one people plan around.
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Towing
Hitches, weight distribution, brake control and trailer security.
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Brake Controller Checker
Answer it from the trailer, not the tow vehicle. Work out what your brakes draw, which controllers are actually rated for your axle count, and when a controller does nothing at all.
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RV Cargo Capacity Calculator
Compare added load with your trailer's cargo label or GVWR minus baseline weight. See water, other cargo and remaining allowance on the same scale.
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RV Tire Age Calculator
Find and decode a tire's DOT date code. See its approximate age and the five-year warranty estimate for Lionshead ST radial tires, separate from condition and replacement guidance.
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RV Towing Payload Calculator
Works out your tongue weight, spends it against the door sticker, and turns it into the hitch rating you need. No green light or red light — the margin in pounds, and the assumptions behind it.
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Ball Mount Drop Calculator
Two measurements and one subtraction give the drop your ball mount needs. Work out the number, see which way to miss if you cannot land on it, and where one-input estimators go wrong.
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RV Tire Pressure Calculator
Find motorhome cold tire pressure from weighed axle ends and Michelin RV tables. Download a Letter/A4 PDF with your weights, selected tire chart and pressure-limit warnings.
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Trailer Lug Nut Torque Calculator
Look up trailer wheel nut torque from Dexter's and Lippert's own tables, in staged passes — and see where the two makers publish figures that do not overlap at all.
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Gear
Leveling, mattresses, storage and the kit that makes a rig livable.
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RV Leveling Block Calculator
Turn a tilt reading into inches at the tire, then into a count of blocks. A ramp is not one block per inch, and every tire on the low side needs its own.
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RV Mattress Size Calculator
Measure the platform and find the RV mattress that fits it — and see why "RV King" is published as three different sizes by three different sellers.
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Camping
Awnings, outdoor cooking, campsite setup and boondocking.
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RV Propane Calculator
Estimate propane remaining and daily use from two cylinder weighings and its stamped tare weight. Compare a 15 lb Blue Rhino exchange fill with a nominal 20 lb refill.
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Maintenance
Sealants, winterizing, storage and troubleshooting that saves a bill.
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RV Winterizing Calculator
Estimate RV antifreeze gallons, check model-specific heater bypass guidance, and download a winterizing checklist with your settings in US Letter or A4.
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