All tools
18 free tools, grouped by what you’re working on. Every one runs in your browser, and nothing you enter is sent anywhere.
Plan & track
See a new setup in 3D, find sizes that fit, check your tires and keep your vehicles’ numbers in one place.
3D wheel & tire fitment studio
Compare your current and new wheel and tire in a 3D view you can rotate 360°: size, poke, tuck, speedometer change and a sheet to take to the shop.Tire size finder
Pick a wheel size and get every tire size within your chosen percentage of the original diameter, closest first.Tire health check
Record tread depth, age, pressure and damage for each tire, see wear patterns and projected tread life, and set a calendar reminder.My Garage & fuel log
Save your vehicles in this browser to fill in any calculator instantly, and keep a fuel log with charts and CSV export. No account.Tires & wheels
Sizes, fitment geometry, sidewall markings, pressure and speedometer error.
Tire size calculator
Sidewall, diameter, circumference and revolutions for any metric size, with a side-by-side comparison and speedometer difference.Wheel offset calculator
See how a new width, offset or spacer moves the inner and outer wheel edges relative to the hub.Backspacing calculator
Convert wheel offset in millimetres to backspacing in inches and back, with front spacing and a labelled cross-section.Tire sidewall & DOT date decoder
Decode a full sidewall marking: size, load index in kg and lb, speed rating, XL, and the DOT week and year of manufacture.Speedometer error calculator
Turn a GPS check or measured distance into a speedometer and odometer correction, with a true-speed table.Tire pressure converter
Convert psi, bar, kPa and kgf/cm², and estimate how tire pressure changes with temperature.Fuel & charging
Trip costs, real-world fuel economy and electric charging costs.
Fuel cost calculator
Trip fuel and cost in L/100 km, km/L, US or imperial MPG, with tolls, parking, cost per person and a two-vehicle comparison.MPG & fuel economy calculator
Work out real fuel economy from your fill-ups and convert between US MPG, imperial MPG, L/100 km and km/L.EV charging cost calculator
Cost of a charge or a trip from battery size, efficiency, electricity price and charging losses, with a fuel comparison.Drivetrain & engine
Gearing, RPM, re-gearing, displacement, compression and power.
Gear ratio calculator
Theoretical road speed at a given RPM, or RPM at a given speed, across every gear, with a speed-versus-RPM chart.Re-gear calculator for bigger tires
The axle ratio that restores your original gearing after a tire diameter change, and how candidate ratios compare.Engine displacement calculator
Displacement in cc, litres and cubic inches from bore, stroke and cylinders, plus bore-stroke ratio and piston speed.Compression ratio calculator
Static compression ratio from bore, stroke, chamber, gasket, deck clearance and piston volume.Horsepower & torque calculator
Convert between torque and power at any RPM, and between hp, kW, PS, N·m and lb·ft.No tool matches that search. Try a broader word such as “tire”, “fuel” or “engine”.