4x4 calculators
Tire size, speedometer error, gearing, fuel range and winch pull. Plain math with the numbers shown, so you can check it.
Tire size & speedometer
Compare your old and new tires. Enter a metric size (like 285/75R16) or a flotation size (like 35x12.50R17).
Airing down on the trail? Use the air-down planner in Tires & Air →
Gearing & RPM
Find your engine speed at highway speed, and the axle ratio that brings bigger tires back to the old feel.
Ratios vary by model, year and transmission. Take yours from the factory service manual, your build sheet or the tag on the axle, not from a forum guess. The top-gear and transfer ratios are just starting values here.
Fuel range
How far you can go, and where your turnaround point is, with a reserve you choose.
Use mileage you've actually seen on dirt, loaded, at elevation. Bigger tires, low range, idling and headwinds can cut it a lot. The rule of thirds (a third out, a third back, a third spare) is a safe default in remote country.
Winch pull
How hard the winch has to pull to move you, and how much it can really pull with the rope you have left on the drum.
Not sure how to rig a double line, a redirect or a bridle? See the winch rigging diagrams →
Load math: weight × surface factor (Penny Hydraulics winch guide; the buried figure is the 4Low Magazine estimate of up to 120%), plus weight × sin(slope). Layer derating follows WARN's published ZEON 8 figures (about 15% less pull on layer 2, then a little less lost on each layer after that); layers past 4 are extrapolated. Your winch's own chart beats these numbers, so use it if you have it.
Results are estimates from the numbers you enter. Tire diameters are calculated from the size on the sidewall; real-world height is usually a little less, especially aired down.