Built for the garage, paddock, and dyno

Make the next change with better numbers

Free automotive calculators and reference tools for fitment, tuning, fuel, and performance. Get a clear answer in seconds—without an account or sending your build data to a server.

Find a tool Decode a VIN

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20 tools

Browse detailed workshops: Wheels & tires Engine & tuning Fuel Performance Vehicle & reference

VIN Decoder
Start with your VIN - full specs, equipment, recall campaigns, and the chassis & engine codes enthusiasts actually use.
Start Here
Tire Size & Speedometer Correction
Compare nominal tire dimensions, speedometer error, and staggered front/rear circumference—with vehicle-specific AWD limits clearly separated.
Most Popular
Datalog Analyzer
Drop in an MHD, JB4, bm3, or EcuTek CSV log. Finds your WOT pulls and grades knock, boost vs target, AFR, IATs, trims, and fuel pressure.
New
Wheel Offset Calculator
Compare wheel width and offset (ET) to see exactly how much further a new wheel pokes out or tucks in.
Fitment
Bolt Pattern & Hub Bore Checker
Will those wheels bolt on? Check PCD and center bore against your car, with hub-centric ring sizing.
Fitment
0-60 & Quarter Mile Estimator
Estimate 0-60, quarter-mile ET, and trap speed from power and weight - or horsepower from a trap speed.
Drag Math
E85 Blend Calculator
Calculate exactly how much E85 and pump gas to add at the pump to hit your target ethanol blend.
Flex Fuel
Octane Blend Calculator
Mix race gas with pump gas - find the mix octane, or how much race fuel hits your target rating.
Race Fuel
Dyno Correction Factor
Normalize dyno numbers to SAE or STD reference weather - compare pulls across days, dynos, and seasons.
Dyno Math
Dyno Sheet Interpreter
Just got dyno'd? Sanity-check the sheet: implied crank HP, trap speed cross-check, and HP-per-liter smell test.
Dyno Math
Gear Ratio & RPM Calculator
Find your engine RPM at any speed given your transmission gear, final drive ratio, and tire size.
Performance
Turbo Boost Pressure Ratio
Convert boost PSI to pressure ratio, or work backwards from a target pressure ratio to required boost.
Forced Induction
Fuel Injector Size Calculator
Size injectors for a target horsepower goal using BSFC, duty cycle, and number of cylinders.
Fuel System
Horsepower ↔ Torque
Convert between horsepower and torque at any RPM using the SAE formula used on every dyno sheet.
Dyno Math
MPG & Fuel Log
Track full and partial fills, weighted real-world MPG or L/100km, and cost per mile. Saves privately in your browser.
Everyday Tool
Fuel Cost Calculator
Calculate cost per mile, monthly, and annual fuel spend. Compare premium vs regular for your car.
Daily Driver
Compression Ratio Calculator
Calculate engine compression ratio from bore, stroke, head gasket thickness, deck clearance, and combustion chamber volume.
Engine Build
AFR & Lambda Calculator
Convert between air-fuel ratio and lambda (λ) for gasoline, E85, ethanol, and diesel fuels.
Tuning
Automotive Unit Converter
Nm ↔ lb-ft, kW ↔ HP ↔ PS, bar ↔ PSI, and every other conversion car people actually need.
Utility
My Garage
Save your car's specs once and every calculator pre-fills with one click. Stored in your browser - no account.
New

New learning center

See the math in a real build decision

View all guides →

Fuel blending

How Much E85 to Make E30?

A 15-gallon worked example using tested E70 pump fuel and E10 gasoline.

6 minute read · Read guide →

Tire fitment

225/45R17 vs 245/40R18

Compare diameter, circumference, speedometer error, and clearance assumptions.

7 minute read · Read guide →

Datalogging

How to Read a Turbo Datalog

Follow boost, throttle, ignition, lambda, and fuel pressure as one timeline.

9 minute read · Read guide →

About TunerBench

TunerBench is a collection of free precision calculators built for performance car enthusiasts, tuners, and builders. Every formula is sourced from SAE standards, factory service manuals, and established motorsport engineering references.

All calculations run entirely in your browser - no data is sent to any server, no account required. Even shared log reports travel inside the link itself, not through us. Use them on your phone in the garage or at your desk before a build.

Who These Tools Are For

Before you use the numbers

Are TunerBench calculators free?

Yes. Every calculator and guide is free to use, with no account or paywall.

Does TunerBench store my VIN or datalog?

No. Calculations and log analysis run in your browser. TunerBench does not upload your VIN, vehicle, or datalog to a server.

Can I use the results to order parts?

Use the results to compare options and plan a build, then verify safety-critical fitment and specifications with the vehicle or parts manufacturer, your tuner, or your engine builder.