Automotive Calculators
ArrayKit's automotive calculators cover the numbers drivers, home mechanics and tuners need to buy, run, repair or modify a vehicle. To identify a car or a fault, the VIN Decoder reads the manufacturer code, country, model year and plant from a 17-character VIN and verifies its check digit, and the OBD2 Code Lookup decodes any check-engine code into its system and subsystem, with likely causes for common ones. For running costs, the Fuel Cost Calculator prices a trip, the Gas Mileage Calculator and Fuel Economy Converter work in MPG, L/100km and km/L, the EV Charging Cost Calculator prices a charge against petrol, and the Mileage Reimbursement Calculator turns miles driven and a per-mile rate into a claim. For tires and wheels, the Tire Size Calculator compares two sizes and the speedometer error a swap causes, the Tire Load Index & Speed Rating tool reads the weight limit and top speed, and the Wheel Offset Calculator converts offset to backspacing, alongside pressure and tread depth tools. Under the hood, the Horsepower Calculator, Engine Displacement Calculator, Compression Ratio Calculator, Gear Ratio Calculator and Air-Fuel Ratio Calculator handle engine and drivetrain math, while the Braking Distance Calculator and Towing Capacity Calculator work out stopping distance and how much you can tow within your ratings. Every calculation and lookup runs in your browser, so VINs, codes and measurements stay on your device.
- Fuel Cost Calculator — Estimate the fuel cost of a trip from distance, efficiency and price.
- Gas Mileage Calculator — Calculate MPG or L/100km from distance and fuel used, and convert.
- Mileage Reimbursement Calculator — Calculate mileage reimbursement from miles driven and a per-mile rate.
- Horsepower Calculator — Calculate horsepower from torque and RPM, or convert power units.
- Engine Horsepower Calculator — Estimate engine horsepower from quarter-mile ET or trap speed.
- Tire Size Calculator — Decode a tire size and compare two sizes for diameter and speedo error.
- VIN Decoder — Decode a 17-character VIN into maker, country, model year and plant, and verify its check digit.
- Fuel Economy Converter — Convert between MPG (US), MPG (UK), L/100km and km/L, with trip fuel and cost.
- Gear Ratio Calculator — Work out speed at RPM, RPM at speed and gear ratios from tooth counts and tyre size.
- Engine Displacement Calculator — Calculate engine displacement in cc, litres and cubic inches from bore, stroke and cylinders.
- Braking Distance Calculator — Stopping distance from speed, reaction time and road surface — thinking plus braking.
- EV Charging Cost Calculator — What a charge costs from battery size, charge window and electricity price, vs petrol.
- Tire Pressure Converter — Convert tyre pressure between psi, bar, kPa and kgf/cm², and correct for temperature.
- Wheel Offset Calculator — Convert wheel offset to backspacing and compare how two wheels sit on the hub.
- Compression Ratio Calculator — Work out static, dynamic and boosted compression ratio from your engine measurements.
- OBD2 Code Lookup — Decode any check-engine trouble code into system, subsystem and likely causes.
- Tire Load Index & Speed Rating — Read the numbers after a tire size as a weight limit and a top speed.
- Towing Capacity Calculator — Work out how much you can really tow from GCWR, GVWR, payload and tongue weight.
- Tire Tread Depth Calculator — Measure remaining tread life, wear rate and when a tire hits the legal limit.
- Octane Blend Calculator — Mix two fuels to a target octane, with ethanol content and cost per gallon.
- Air-Fuel Ratio Calculator — Convert AFR, lambda and phi for gasoline, E85, diesel, methanol and more.
Guides
Frequently asked questions
- What can I do with these automotive calculators?
- Work out trip fuel and EV charging costs, convert fuel economy and tire pressure units, decode a VIN or an OBD2 trouble code, and compare tire sizes, load ratings and wheel offsets. Tuners and home mechanics can estimate horsepower, displacement, compression ratio, gearing, air-fuel ratio and octane blends, and any driver can check stopping distance, towing limits and remaining tread life.
- Which fuel calculator should I use?
- Use the Gas Mileage Calculator to find your car's real economy from a fill-up: the distance driven and the fuel it took. The Fuel Economy Converter switches a figure between US MPG, UK MPG, L/100km and km/L, the Fuel Cost Calculator prices a trip from its distance, economy and fuel price, and the EV Charging Cost Calculator prices a battery charge and compares the running cost with petrol.
- Is the VIN or anything else I enter sent to a server?
- No. Every automotive calculator runs in your browser. The VIN Decoder and OBD2 Code Lookup work from the structure of the VIN or code and a built-in table instead of querying an online database, so the VINs, codes and measurements you type are not uploaded.
- How accurate are the automotive calculators?
- They apply standard formulas and published charts, such as horsepower from torque × RPM ÷ 5252, drag-strip formulas that estimate power from a quarter-mile run, the load index and speed rating tables, and a friction value for each road surface in the braking model. Results are estimates, so a dyno sheet, your tire shop, the door-jamb placard and the owner's manual remain the authority on real power, fitment, pressures and towing ratings.
- Do the automotive calculators work in metric and imperial units?
- Yes. The Fuel Economy Converter moves between US MPG, UK MPG, L/100km and km/L, the Tire Pressure Converter shows psi, bar, kPa and kgf/cm² together, the Braking Distance Calculator works in km/h with meters or mph with feet, and the Towing Capacity Calculator switches between pounds and kilograms. Tire sizes use the standard metric format such as 225/45R17, and the Tire Tread Depth Calculator accepts 32nds of an inch or millimeters.