Free Tire & Wheel Calculators
Real calculators for tire size, wheel offset, bolt pattern, DOT age, load and pressure — plus Vehicle Fit for your make and model.
Vehicle Fit
Look up bolt pattern, offset, center bore and factory wheel specs by year, make and model.
Tire size
Free Tire Size Calculator
Paste a size. See the real dimensions — not just the numbers on the sidewall.
Free Tire Size Comparison Calculator
The tool people actually need: will this size change height, width and speedometer — and is it inside 3%?
Tire Size Converter — Metric/Inches
Exact geometry first. Then the closest size you can actually buy — with the difference stated.
Tire Size Chart — Metric & Inches
Common sizes by rim diameter — metric, exact inches, and a link to run the numbers.
Speedometer Error Calculator
Taller tire: you are going faster than the needle. Shorter tire: you are going slower.
Plus Sizing Calculator
Bigger rim, shorter sidewall — without accidentally lifting or lowering the car.
Reverse Tire Size Finder
You want about 33 inches. We list real sizes that actually sit there — not a fake 273/61R20.
Odometer Correction Calculator
The needle is a different tool. This one is about the mile counter — oil changes, warranties, resale.
Staggered Fitment Checker
Bigger in the rear is a look. The number that matters is how different the two diameters are.
Wheel geometry
Free Wheel Offset Calculator
More positive offset tucks the wheel in. More width with the same offset pokes both ways.
Offset to Backspacing Converter
Offset is from the centerline, in mm. Backspacing is from the back lip, in inches. They need the rim width to talk to each other.
Rim Width Calculator by Tire Size
Measuring width is where the tire is spec’d. Acceptable is the full range. Optimal is near measuring.
Free Bolt Pattern Converter — 5x114.3
5x114.3 mm is 5x4.5". 5x112 is not. Close is not a fit.
Wheel Spacer Calculator
A spacer pushes the wheel out. On slip-on hardware it also eats stud thread. Measure; do not guess.
Hub-Centric Ring Calculator
The ring’s outside matches the wheel. The inside matches the hub. It does not move the lug holes.
Tire Stretch Calculator
The verdict is the published rim-width table. A percentage is just how the picture looks.
Gearing
Regear Calculator — Restore Cruise RPM
Taller tires are like a taller gear. We calculate the ratio that puts cruise RPM back. We do not tell you to buy 4.56.
RPM at Speed Calculator
How fast the engine is turning at 65. Diameter and gears, not a guess from a forum chart.
Crawl Ratio Calculator
How much the tires are reduced in 1st and 4-low. It is just three numbers multiplied.
Wear & cost
Tire Wear Pattern Guide
The tread is a clue. It is not a work order. Pick the pattern you see; we tell you what to check.
Tire Cost Per Mile Calculator
Cheap tires that die early are not cheap. The unit that matters is dollars per mile.
Prorated Tire Value Calculator
What is left is the tread above the wear bars, not the full original depth.
Age, load & pressure
Free DOT Tire Age Calculator
The last group in the DOT stamp is the week and year. Age is a safety conversation, not a law.
Tread Depth Calculator
Wear bars sit at 2/32". How you get there depends on how fast you have been using tread.
Tire Load Index Chart & Speed Ratings
The number before the letter (91H) is load. The letter is speed. Both have to meet the door-jamb spec.
PSI to kPa to Bar Converter
The sidewall number is a maximum. The door sticker is what the car wants. Convert units here — do not mix them up.
Cold vs Hot Tire Pressure Calculator
Air in a closed tire follows temperature. Check cold. Do not bleed a hot tire down to the door sticker.
Load Range to Ply Rating Converter
E is a 10-ply rating class, not ten belts. It is not a number of pounds by itself.
Tire Load Capacity vs Axle Weight
Will these tires hold that axle? We add the pounds from the load-index table. We do not invent an air pressure.
Questions
- Did Vehicle Fit move to /tools?
- No. Vehicle Fit still lives at /fit and /fit/[vehicle]. This hub only links to it.
- Do these calculators replace a shop?
- No. They give geometry and interpretation. Rubbing, load index and a misread bolt pattern still get confirmed in person.
- Can I share a result?
- Yes — the link keeps the numbers. Those URLs are not indexed; the canonical is always the clean tool page.
