// Free tuning tools
Performance,
dialed in.
Fast, ad-free calculators for people who actually turn the wrenches — plus the guides that explain them and a build planner to spec your car. No sign-up, no fluff, works on your phone in the garage.
// Calculators
All 34, grouped by what you are working on. Each one draws its answer and explains the number.
Wheels & tires
Fitment, sizing and the numbers that decide whether a wheel clears.
Engine builder
Displacement, compression, cam timing and how much air the engine can actually move.
Forced induction
Compressor sizing, pressure ratio and what boost does to effective compression.
Fuel & tuning
Injectors, AFR and lambda, ethanol blending and running costs.
Chassis & handling
Spring rates, brake bias, corner weights and alignment units.
Performance & drag strip
Power-to-weight, acceleration estimates, trap speed maths and dyno correction.
See all 34 side by side — what each works out and what it needs →
// Built for the garage
The same habits in every calculator, so you only learn them once.
Checked maths
Every calculator is run against known answers by an automated test before any change ships.
Share the exact result
Copy link puts every input and unit in the URL, so whoever opens it sees your numbers.
Use my car
Save your car once in My Build, and one tap fills in any calculator that needs its specs.
Works with no signal
Pages you have opened keep working offline, and so does the whole OBD-II code lookup.
Metric or imperial
Switch units where it matters, and your choice follows you to the next calculator.
Find anything fast
Press / or tap the search icon on any page to jump to a calculator, guide or cheat sheet.
Prints clean
Cheat sheets are made for the workshop wall, and every page prints without the menus.
Nothing to sign up for
No ads, no account, no cookies. Your builds stay in your browser unless you share them.
// Build planner
My Build — your car, in every calculator
Spec your car once — power, weight, tires, gearing — and keep it in your browser. No account, nothing uploaded.
- Use my car fills a calculator with your specs in one tap
- Garage keeps every build, and compares two or more side by side
- Share a build as a link, or save it as a PNG sheet for the forums
- Back up the whole garage to a file and restore it on another device
// Play
Three games, each with a weekly and an all-time leaderboard.
Tune It
Dial in the fuel curve, run the dyno and chase peak power — go too lean and it knocks.
GameReaction Time Test
Drag-strip Christmas tree — stage up, wait for green and launch. Beat your best, don't red-light.
GameDrag Race
Launch your My Build car down the ¼-mile — tree start, manual shifts, chase your best ET.
// Guides
How to read a tire size
Every number on the sidewall — width, aspect, load index & speed rating.
GuideWheel offset explained
ET, backspacing and poke — and whether a wheel will clear.
GuideCompression ratio explained
What it is, how it's calculated and what a good ratio is.
GuideAFR & lambda explained
Mixture, tuning targets and why lambda beats a bare AFR number.
GuidePower-to-weight explained
The number that really predicts pace, and how to compare fairly.
AllAll 22 guides →
Plain-English explainers for the maths behind the mods — turbos, E85, brake bias, cams and more.
// Reference
Tuning glossary
Every term the calculators use — AFR, lambda, offset, LSA, duty cycle — defined in one line, linked to the tool that uses it.
PrintableCheat sheets
8 one-page reference cards built to print clean and live above the workbench — AFR targets, injector flow, alignment, PCDs, air density.
GuidedDiagnose
Step-by-step fault finding for the questions a calculator cannot answer — will these wheels fit, why is my AFR off, where is my quarter-mile time going.
1,238 codesOBD-II code lookup
Search generic P0, P2 and U0 trouble codes by number or keyword — meaning, symptoms and the checks worth doing before replacing a part.
Start with the tire size calculator
The most-used tool — diameter, gearing and speedo error in one screen.