From horsepower and quarter-mile trap speed to towing limits, tire sizes, and EV charging costs, this is a complete set of free automotive calculators for anyone who works on, tows with, or shops for a vehicle.
Every tool runs instantly in your browser with no sign-up, shows the formula and a worked example, and links to related calculators so you can move from one question to the next. Pick a category below or search by name.
🏎️ Engine & Performance 9
Air-Fuel Ratio CalculatorHome » Automotive CalculatorsCALCULATOR Measured AFR Fuel typeGasoline (14.7)Diesel (14.6)E85 (9.8)Ethanol (9.0)Methanol (6.4) —Lambda —Stoich AFR —Equivalence Ratio —Your AFR […]Compression Ratio CalculatorHome » Automotive CalculatorsCALCULATOR Bore Stroke Bore/stroke/clearance unitInchesMillimeters Number of cylinders Combustion chamber (cc) Piston dish (+) / dome (-) […]Engine Displacement CalculatorHome » Automotive CalculatorsCALCULATOR Bore Stroke Cylinders Bore / stroke unitMillimetersInches —Displacement —In CC —Cubic Inches —Per Cylinder — Bore […]Engine Torque CalculatorHome » Automotive CalculatorsCALCULATOR Horsepower (hp) Engine speed (RPM) —Torque —Torque (N·m) —Power (kW) —Power (PS) — Have torque instead? […]Horsepower CalculatorHome » Automotive CalculatorsCALCULATOR Torque (lb-ft) Engine speed (RPM) DrivetrainFront-wheel drive (~10% loss)Rear-wheel drive (~15% loss)All-wheel drive (~20% loss) —Horsepower […]Injector Size CalculatorHome » Automotive CalculatorsCALCULATOR Target horsepower Number of injectors BSFC (lb/hp/hr) Max duty cycle (%) —Injector Size —In cc/min —Total […]Power-to-Weight Ratio CalculatorHome » Automotive CalculatorsCALCULATOR Power (hp) Weight (lb) —Power-to-Weight —Pounds per HP —Watts per kg —HP per 1000 lb — […]Quarter Mile ET CalculatorHome » Automotive CalculatorsCALCULATOR Vehicle weight incl. driver (lb) Horsepower (flywheel) —Quarter Mile ET —Trap Speed —ET (Street Estimate) —Power-to-Weight […]Quarter Mile Trap Speed CalculatorHome » Automotive CalculatorsCALCULATOR Horsepower (at wheels or crank) Vehicle weight (lb, with driver) —Trap Speed —Trap Speed (km/h) —Weight […]
🚚 Towing & Truck 9
Axle Weight CalculatorHome » Automotive CalculatorsCALCULATOR Front GAWR (lb) Rear GAWR (lb) Front axle weight (lb) Rear axle weight (lb) —Front Margin […]Cargo Load CalculatorHome » Automotive CalculatorsCALCULATOR Payload capacity (lb) Passengers (lb) Gear and accessories (lb) Trailer tongue weight (lb) —Remaining Cargo —Weight […]GCWR CalculatorHome » Automotive CalculatorsCALCULATOR GCWR (lb) Loaded truck weight (lb) Loaded trailer weight (lb) —Combined Weight —Remaining Margin —Capacity Used […]GVWR CalculatorHome » Automotive CalculatorsCALCULATOR GVWR (lb) Curb weight (lb) Added load now (lb) —Payload Capacity —Current Total —Can Still Add […]Payload CalculatorGVWR — gross vehicle weight rating (lb) Curb weight (lb) Passengers (lb) Cargo in cab and bed (lb) Trailer tongue […]Pin Weight CalculatorHome » Automotive CalculatorsCALCULATOR Loaded trailer weight (lb) Pin weight (% of trailer) Truck payload available (lb) —Pin Weight —Recommended […]Tongue Weight CalculatorHome » Automotive CalculatorsCALCULATOR Gross trailer weight, loaded (lb) Trailer typeConventional / bumper-pull (10-15%)Fifth-wheel / gooseneck (15-25%) Measured tongue weight […]Towing Capacity CalculatorGCWR — gross combined weight rating (lb) Tow vehicle curb weight (lb) Passengers + cargo in vehicle (lb) Loaded trailer […]Trailer Weight CalculatorHome » Automotive CalculatorsCALCULATOR Trailer dry / empty weight (lb) Cargo loaded (lb) Trailer GVWR rating (lb) Tow vehicle trailer […]
🛞 Tire & Wheel 9
Rim Width Tire Size CalculatorHome » Automotive CalculatorsCALCULATOR Rim width (in) —Ideal Tire Width —Minimum —Maximum —Rim Width — Have a tire in mind? […]Tire Circumference CalculatorHome » Automotive CalculatorsCALCULATOR Tire diameter (in) —Circumference —Circumference (ft) —Circumference (m) —Revs per Mile — Distance for a number […]Tire Clearance CalculatorHome » Automotive CalculatorsCALCULATOR Current diameter (in) Current width (mm) New diameter (in) New width (mm) —Diameter Change —Height Gain […]Tire Diameter CalculatorHome » Automotive CalculatorsCALCULATOR Tire width (mm) Aspect ratio (%) Wheel diameter (in) —Overall Diameter —Diameter (mm) —Sidewall Height —Sidewall […]Tire RPM CalculatorHome » Automotive CalculatorsCALCULATOR Tire diameter (in) Speed (mph) —Revs per Mile —Tire RPM at Speed —Circumference —Distance per Rev […]Tire Size CalculatorTire size (optional, e.g. 225/45R17) Tire width (mm) Aspect ratio (%) Wheel diameter (in) –Overall diameter –Sidewall height –Circumference –Revs […]Tire Size Comparison CalculatorCompare two tire sizes by overall diameter and see the speedometer error and whether the change is within 3%.Wheel Backspacing CalculatorHome » Automotive CalculatorsCALCULATOR Wheel width (in) Offset (mm) —Backspacing —Offset (mm) —Offset (in) —Front Spacing — Know the backspacing? […]Wheel Offset CalculatorHome » Automotive CalculatorsCALCULATOR Current wheel width (in) Current offset (mm) New wheel width (in) New offset (mm) —Outer Edge […]
⚡ Electrical 8
12V Battery Runtime CalculatorHome » Automotive CalculatorsCALCULATOR Battery voltage12V24V48V Battery capacity (Ah) Load (watts) Usable capacity (%) Efficiency (%) —Estimated Runtime —Usable Energy […]12V Wire Size CalculatorHome » Automotive CalculatorsCALCULATOR System voltage12V24V48V Current (amps) One-way length (ft) Max voltage drop (%) ConductorCopperAluminum —Recommended Wire Gauge —Voltage […]Alternator Size CalculatorHome » Automotive CalculatorsCALCULATOR System voltage12V24V Total electrical load (A) Alternator rated output (A) Output at idle (% of rated) […]Amplifier Power CalculatorHome » Automotive CalculatorsCALCULATOR Amplifier RMS power (W) Amplifier classClass D (~80%)Class AB (~60%)Class A (~25%) Running voltage (V) —Max […]Battery Capacity CalculatorHome » Automotive CalculatorsCALCULATOR Battery voltage (each)6V12V Capacity each (Ah) Batteries in series Strings in parallel Usable capacity (%) —System […]Fuse Size CalculatorHome » Automotive CalculatorsCALCULATOR Continuous load (amps) Safety factor (%) —Recommended Fuse —Minimum Rating —Safe Continuous —Load Current — Find […]Inverter Load CalculatorHome » Automotive CalculatorsCALCULATOR AC load (watts) Inverter efficiency (%) Battery voltage12V24V48V Battery capacity (Ah) Usable capacity (%) Load type […]Voltage Drop CalculatorHome » Automotive CalculatorsCALCULATOR Current (amps) Wire length one-way (ft) Wire gauge (AWG)681012141618 System voltage (V) —Voltage Drop —Drop Percent […]
⛽ Fuel Economy & Cost 8
Cost Per Mile CalculatorHome » Automotive CalculatorsCALCULATOR Annual miles Fuel price ($/gal) Fuel economy (MPG) Maintenance & repairs ($/yr) Tires ($/yr) Insurance ($/yr) […]E85 Blend CalculatorHome » Automotive CalculatorsCALCULATOR E85 ethanol (%) Pump gas ethanol (%) Target ethanol (%) Total volume (gal) —E85 to Add […]EV vs Gas Cost CalculatorHome » Automotive CalculatorsCALCULATOR Miles per year Gas car MPG Gas price ($/gal) EV efficiency (mi/kWh) Electricity price ($/kWh) —Gas […]Fuel Cost CalculatorEstimate the gas cost of a trip from distance, MPG, and fuel price, with round-trip totals and cost splitting.Fuel Savings CalculatorHome » Automotive CalculatorsCALCULATOR Current MPG New MPG Miles driven per year Gas price ($/gal) —Annual Savings —Current Annual Cost […]MPG CalculatorCalculate real-world miles per gallon from miles driven and gallons used, with cost per mile and L/100km.Octane Blend CalculatorHome » Automotive CalculatorsCALCULATOR Lower octane Higher octane Target octane Total volume (gal) —Higher-Octane Gas —Lower-Octane Gas —Higher-Octane Share —Resulting […]Trip Fuel Cost CalculatorHome » Automotive CalculatorsCALCULATOR Trip distance (miles) Fuel economy (mpg) Gas price ($/gal) —Trip Cost —Fuel Used —Cost per Mile […]
🛢️ Fluids & Maintenance 7
Antifreeze Dilution CalculatorHome » Automotive CalculatorsCALCULATOR Cooling system capacity (qt) Target antifreeze concentration (%) —Concentrate Needed —Distilled Water —Mix —Est. Freeze Point […]Brake Fluid CalculatorHome » Automotive CalculatorsCALCULATOR VehicleMotorcycleCompact carMidsize carSUV / TruckHeavy-duty truck ServiceBleed onlyFull flush Bottle size12 fl oz (355 mL)16 fl […]Coolant Mix CalculatorHome » Automotive CalculatorsCALCULATOR Cooling system capacity UnitQuartsGallonsLiters Target antifreeze % Concentrate strength % —Antifreeze (Concentrate) —Water —Freeze Protection —Boil […]Oil Capacity CalculatorHome » Automotive CalculatorsCALCULATOR Engine oil capacity Capacity unitQuarts (qt)Liters (L) Container size to buy1-quart bottle5-quart jug1-liter bottle5-liter jug —Oil […]Oil Mix CalculatorHome » Automotive CalculatorsCALCULATOR Amount of gas Gas unitUS gallonsLiters Mix ratio (gas : 1 oil) —Oil to Add —Oil […]Transmission Fluid CalculatorHome » Automotive CalculatorsCALCULATOR Total ATF capacity (qt) Drain & fill recovery (%) —Drain & Fill —Full Exchange —Full in […]Washer Fluid Mix CalculatorHome » Automotive CalculatorsCALCULATOR Amount to make UnitUS gallonsLiters Mix (concentrate : water)Full strength1 : 11 : 21 : 31 […]
🚙 Off-Road & 4x4 7
Approach Angle CalculatorHome » Automotive CalculatorsCALCULATOR Front overhang (in) Lowest front point height (in) —Approach Angle —Equivalent Grade — How your angle […]Breakover Angle CalculatorHome » Automotive CalculatorsCALCULATOR Wheelbase (in) Lowest belly clearance (in) —Breakover Angle —Ramp Grade Each Side — How your angle […]Crawl Ratio CalculatorHome » Automotive CalculatorsCALCULATOR Transmission 1st gear ratio Transfer case low ratio Axle (differential) ratio Tire diameter (in) Engine idle […]Departure Angle CalculatorHome » Automotive CalculatorsCALCULATOR Rear overhang (in) Lowest rear point height (in) —Departure Angle —Equivalent Grade — How your angle […]Ground Clearance CalculatorHome » Automotive CalculatorsCALCULATOR Current ground clearance (in) Current tire diameter (in) New tire diameter (in) —Current Clearance —Clearance Gained […]Lift Height CalculatorHome » Automotive CalculatorsCALCULATOR Suspension lift (in) Body lift (in) Current tire diameter (in) New tire diameter (in) —Total Lift […]Wheel Travel CalculatorHome » Automotive CalculatorsCALCULATOR Shock stroke (in) Motion ratio (wheel / shock) Compressed at ride height (%) —Total Wheel Travel […]
⚙️ Transmission & Drivetrain 6
Axle Torque CalculatorHome » Automotive CalculatorsCALCULATOR Driveshaft torque (lb-ft) Axle ratio Axle efficiency (%) —Axle Torque —Per Wheel (open diff) —Axle Ratio […]Differential Ratio CalculatorHome » Automotive CalculatorsCALCULATOR Axle (differential) ratio Transmission gear ratio (top gear) Tire diameter (in) Speed (mph) —Engine RPM at […]Final Drive Ratio CalculatorHome » Automotive CalculatorsCALCULATOR Transmission gear ratio Axle (differential) ratio —Final Drive Ratio —Torque Multiplier —Trans Gear —Axle Ratio — […]Gear Ratio CalculatorHome » Automotive CalculatorsCALCULATOR Driven gear teeth (output) Drive gear teeth (input) —Gear Ratio —Torque Multiplier —Output Speed —Type — […]Transmission RPM CalculatorHome » Automotive CalculatorsCALCULATOR Speed (mph) Transmission gear ratio Axle ratio Tire diameter (in) —Engine RPM —MPH per 1000 RPM […]Wheel Torque CalculatorHome » Automotive CalculatorsCALCULATOR Engine torque (lb-ft) Transmission gear ratio Axle ratio Driveline efficiency (%) Tire diameter (in) —Wheel Torque […]
🔌 EV Calculators 6
Battery Degradation CalculatorHome » Automotive CalculatorsCALCULATOR Original capacity (kWh) Current capacity (kWh) Efficiency (mi/kWh) —State of Health —Capacity Lost —Range Lost —Remaining […]EV Charging Cost CalculatorBattery capacity (kWh) Current charge (%) Target charge (%) Electricity price ($/kWh) Charging efficiency (%) Efficiency (mi/kWh, optional) –Charging cost […]EV Charging Time CalculatorBattery capacity (kWh) Current charge (%) Target charge (%) Charger power (kW) Charging efficiency (%) Efficiency (mi/kWh, optional) –Charging time […]EV Efficiency CalculatorHome » Automotive CalculatorsCALCULATOR Distance driven (mi) Energy used (kWh) —Efficiency —Consumption —MPGe —km per kWh — Cost to drive […]EV Range CalculatorHome » Automotive CalculatorsCALCULATOR Usable battery (kWh) Efficiency (mi/kWh) Charge to use (%) —Range —Energy Used —Range (km) —Consumption — […]Gas vs Hybrid vs EV Cost CalculatorHome » Automotive CalculatorsCALCULATOR Gas Car Gas car price ($) Gas car MPG Gas price ($/gal) Hybrid Hybrid price ($) […]
🌀 Suspension 6
Coil Spring CalculatorHome » Automotive CalculatorsCALCULATOR Wire diameter (in) Mean coil diameter (in) Active coils Shear modulus G (Mpsi) —Spring Rate —Rate […]Motion Ratio CalculatorHome » Automotive CalculatorsCALCULATOR Wheel travel measured (in) Spring travel measured (in) Spring rate (lb/in) —Motion Ratio —Wheel Rate —Rate […]Shock Travel CalculatorHome » Automotive CalculatorsCALCULATOR Extended length (in) Compressed length (in) Installed length at ride height (in) —Shock Stroke —Up-Travel —Droop […]Spring Rate CalculatorHome » Automotive CalculatorsCALCULATOR Force applied (lb) Deflection (in) —Spring Rate —Rate (N/mm) —Rate (kgf/mm) —Travel per 100 lb — […]Suspension Frequency CalculatorHome » Automotive CalculatorsCALCULATOR Corner sprung weight (lb) Spring rate (lb/in) Motion ratio (wheel / spring) —Ride Frequency —Wheel Rate […]Wheel Rate CalculatorHome » Automotive CalculatorsCALCULATOR Spring rate (lb/in) Motion ratio (wheel / spring) —Wheel Rate —Lost to Leverage —Effective Efficiency —Wheel […]
📐 Auto 5
Alternator Sizing CalculatorHome » Automotive CalculatorsCALCULATOR Size an alternator for your electrical load. Add up your accessory draw, include the base vehicle […]Battery Charging Time CalculatorHome » Automotive CalculatorsCALCULATOR Estimate how long it takes to charge a 12-volt battery from its amp-hour capacity, how far […]Engine RPM CalculatorHome » Automotive CalculatorsCALCULATOR Find your engine RPM at a cruising speed for a given tire size, transmission gear, and […]Fuel Economy CalculatorHome » Automotive CalculatorsCALCULATOR Enter the distance you drove and the fuel it took to get your fuel economy in […]Speedometer Error CalculatorHome » Automotive CalculatorsCALCULATOR Fitting a different tire size changes how fast you really go for a given speedometer reading. […]
🎨 Paint & Body 4
Auto Paint Coverage CalculatorHome » Automotive CalculatorsCALCULATOR Area to paint (sq ft) Number of color coats Coverage per gallon, 1 coat (sq ft) […]Body Filler CalculatorHome » Automotive CalculatorsCALCULATOR Repair area (sq ft) Average thickness (in) —Filler Volume —Cubic Inches —Cream Hardener —Quarts to Buy […]Clear Coat Coverage CalculatorHome » Automotive CalculatorsCALCULATOR Area to clear (sq ft) Clear coats Coverage per gallon, 1 coat (sq ft) Overspray waste […]Vinyl Wrap CalculatorHome » Automotive CalculatorsCALCULATOR Vehicle sizeCompact carSedan / coupeSUV / crossoverPickup truckVan / large SUV CoverageFull wrapPartial wrapAccents / roof […]
🛑 Brakes 4
Brake Bias CalculatorHome » Automotive CalculatorsCALCULATOR Front piston area (sq in) Front rotor radius (in) Rear piston area (sq in) Rear rotor […]Brake Horsepower CalculatorHome » Automotive CalculatorsCALCULATOR Vehicle weight (lb) Speed before braking (mph) Speed after braking (mph) Stopping time (s) —Average Braking […]Brake Torque CalculatorHome » Automotive CalculatorsCALCULATOR Line pressure (psi) Caliper piston area (sq in) Pad friction (mu) Effective rotor radius (in) —Brake […]Stopping Distance CalculatorEstimate total stopping distance from speed, reaction time, and road conditions, in feet, car lengths, and meters.
💰 Finance & Ownership 3
Auto Loan CalculatorAn auto loan calculator is also known as a car loan calculator - the two terms mean the same thing. You borrow the price of the vehicle minus...Car Lease CalculatorEstimate a monthly car lease payment from price, residual, money factor, and term, with depreciation and finance breakdown.Mileage Reimbursement CalculatorTotal your mileage reimbursement from miles, rate, and trips, with round-trip and per-trip figures. Not tax advice.
What you can calculate here
The library is grouped into more than a dozen categories. Engine and performance tools cover horsepower, torque, compression ratio, and quarter-mile trap speed. Fuel tools handle MPG, trip cost, and gas-versus-EV comparisons. Tire and wheel tools decode sizes, diameters, offsets, and clearance. Drivetrain tools work out gear and final-drive ratios. Towing and truck tools keep you inside payload, tongue-weight, and GVWR limits. Rounding it out are electrical, brake, suspension, fluid, paint and body, EV, and off-road calculators.
Who these calculators are for
DIY mechanics use them to size fuses, mix coolant, and check spring rates. Truck and trailer owners lean on the towing and payload tools to load safely. EV shoppers compare running costs and charging times against gas. Off-roaders plan lift heights and clearance angles. Racers and tuners estimate horsepower from trap speed and dial in gear ratios. If you have ever needed a quick, reliable number without digging through a service manual, these are built for you.
Getting accurate results
A few habits make the numbers trustworthy:
- Pull weights from the door-jamb sticker (GVWR and payload) rather than estimating.
- For trap speed and power-to-weight, use race weight: the vehicle with fuel and driver aboard.
- Mix coolant with distilled water and confirm the result with a refractometer, not just the poured ratio.
- Measure tire and suspension dimensions where you can. Small differences move the result more than you might expect.
Frequently asked questions
Are these calculators free?
Yes. Every calculator on Formula Factory is free to use, with no account, no paywall, and no usage limit.
Do I need to sign up or install anything?
No. They run entirely in your browser on desktop or phone. Nothing to download and nothing to register for.
How accurate are the results?
The formulas are standard engineering and industry equations, so results are accurate for the inputs you give. Real-world factors like temperature, wear, and tolerances can shift outcomes, so treat the numbers as solid estimates and confirm anything safety-critical against the manufacturer specs.
Will they work on my phone?
Yes. Every tool is responsive and behaves the same on mobile, tablet, and desktop.
Which calculator should I start with?
Start from the question you actually have. Towing something? Try Towing Capacity or Payload. Changing wheels? Tire Size Comparison. Shopping for an EV? EV vs Gas Cost. Each tool links to related ones so you can keep going.
Do you store the numbers I enter?
No. Calculations happen in your browser, and your inputs are not saved or sent anywhere.