Tire Size Comparison Calculator
Parse metric (225/45R17) or flotation (33x12.5R15) tire codes, get sidewall height, overall diameter, circumference and revolutions per mile/km, and compare two sizes with the resulting speedometer error.
Processed entirely in your browser — nothing you enter here is ever uploaded.
Result
About this tool
This page opens the tire size calculator ready to compare any two tires against each other. Type the code for your current tire on the left and the size you are considering on the right — metric codes like 225/45R17 and flotation codes like 33x12.5R15 both work, and you can even compare one of each.
The tool converts both sizes to the same set of measurements — sidewall height, overall diameter, circumference, and revolutions per mile and per kilometer — so a low-profile metric tire and a tall flotation tire land on a common, comparable scale. A to-scale diagram shows the rim and the full tire outline for both sizes next to each other.
Below the numbers, the comparison block spells out the diameter difference in inches and percent, and translates that into a speedometer reading error: fit a taller tire and your speedometer will under-read your real speed; fit a shorter one and it will over-read. Everything is calculated locally — no size or vehicle data leaves your browser.
Example. The code 225/45R17 has a sidewall of 101.25 mm and an overall diameter of 634.3 mm.
Limit. Metric sizes must match the width/aspectRrim pattern and flotation sizes the diameter x width R rim pattern; width is limited to 100–400 mm.