Know Your Tires Before You Buy or Swap

Calculate exact internal air volume of any tire in liters, gallons & cubic inches — useful for sealant dosing and capacity comparison.

Find how much your speedometer reads off after a tire size change — get real speed at any indicated reading and odometer error %.

Calculate static, loaded, and dynamic rolling radius plus circumference and revs per mile for any P-metric tire.

Convert wheel ET offset to backspacing and estimate outer poke and inner clearance for custom fitment.

Check if staggered front/rear tires are safe for AWD and xDrive — compares diameter difference and rolling radius.

Calculate exact scrub radius from SAI, spindle offset, and wheel ET — or instantly see how a wheel swap or spacer shifts your scrub radius, with drivetrain safety rating.

Find minimum, ideal, and maximum rim width for any tire section width based on industry correlation tables.

Convert between P-Metric and Flotation tire sizes and compare two sizes with diameter, sidewall, and speedometer error.

Calculate tire contact patch area in sq in and cm² from vehicle load and inflation pressure.

Find recommended tire pressure by vehicle type and convert PSI ↔ kPa instantly.

Instantly convert tyre pressure between PSI and kPa — perfect for UK and European vehicles.

Decode your tire DOT code to find manufacture date and age — get a safety warning if tires are over 6 years old.

Compare spare tire diameter to primaries and check AWD/4WD tolerance to avoid drivetrain damage.

Compare two tire sizes side-by-side — diameter, sidewall, speedometer error, and revs/mile instantly.

Find the exact diameter difference between two tire sizes with safe-change %, speedometer error, and AWD tolerance.

Solve for the aspect ratio needed to hit a target diameter — ideal for plus-sizing while keeping speedometer error under ±3%.

Understand UTQG temperature grades (A, B, C) and what they mean for heat resistance and high-speed safety.

Estimate inner suspension clearance and outer fender poke when changing wheel width, offset, or tire size.

Check if your tire width is compatible with your rim — see stretch or pinch estimate and safety bands.

Find Plus-0, Plus-1, and Plus-2 tire sizes within safe diameter range with speedometer error and fitment impact.

Calculate remaining tread life from depth in 32nds or mm and decode UTQG treadwear ratings.

Convert tire speed rating letters (Q–ZR) to max safe speed in mph and km/h with OEM matching guidance.

Calculate exact sidewall height in mm and inches from tire width and aspect ratio.

Convert tire Load Range (SL, XL, C–H) to ply rating, max PSI, and typical use for LT and trailer tires.

Convert tire Load Index to max load capacity in lbs and kg — match it to your vehicle GVWR safely.

See how bigger tires affect effective gear ratio and RPM — calculate the regear needed to restore stock performance.

Understand positive, negative, and zero caster — how it affects steering feel, self-centering, and tire wear.

Calculate engine RPM at any speed from tire size, axle ratio, and gear — see the RPM impact of bigger tires.

Understand toe-in, toe-out, and zero toe — how small changes affect stability, turn-in, and tire wear.

Compare any two tire sizes with a to-scale visual diagram, bar charts, and live speedometer simulation.

Calculate tire revolutions per mile/km, rolling circumference, and speedometer error after a size change.

Check tire stretch or pinch for any tire and rim combo — see safe limits and street vs show risk levels.

Estimate prorated tire value and remaining tread life — useful for warranty claims, insurance, and used tire sales.

Calculate BMW tire fitment for any model — compare OEM vs aftermarket sizes, check xDrive 1% rolling diameter rule, M-series staggered specs, and speedometer error.

Complete MX-5 Miata tire calculator for NA, NB, NC, ND — decode sizes, compare stock vs new with speedometer correction, check generation-specific fender clearance, and get track-day recommendations.