Calculate revolutions per mile from tire size or overall diameter, with results in rev/mi, rev/km, diameter, and circumference values.
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Rev Per Mile Formula
The calculator finds tire revolutions per mile by dividing the number of inches in one mile by the tire circumference. If you enter a tire size, it first converts the tire size into an overall diameter.
Overall diameter mode
Rev/mi = 63360 / (pi * D)
Tire size mode
Sidewall = (W * (A/100)) / 25.4
D = R + 2 * Sidewall
Rev/mi = 63360 / (pi * D)
Revolutions per kilometer
Rev/km = Rev/mi / 1.609344
- Rev/mi = tire revolutions per mile
- Rev/km = tire revolutions per kilometer
- D = overall tire diameter in inches
- W = tire section width in millimeters
- A = aspect ratio as a percent
- R = rim diameter in inches
- Sidewall = sidewall height in inches
- 63360 = inches in one mile
- pi = approximately 3.14159
The tire size function uses the width, aspect ratio, and rim diameter from the tire sidewall. It calculates sidewall height, doubles it, adds the rim diameter, and then uses that diameter to find revolutions per mile.
The overall diameter function skips the tire-size conversion. It uses the diameter you enter directly after converting millimeters or centimeters to inches if needed.
The calculator also shows tire circumference because revs per mile are based on how far the tire travels in one full turn.
Typical Tire Revolutions Per Mile Ranges
| Rev/mi range | Common tire type | General meaning |
|---|---|---|
| 900+ | Small passenger tire | Small diameter, more turns per mile |
| 750 to 900 | Typical passenger car tire | Common range for sedans, coupes, and smaller crossovers |
| 600 to 750 | SUV or light-truck tire | Larger diameter, fewer turns per mile |
| Below 600 | Large off-road tire | Very large diameter, low revolutions per mile |
Example Calculations
Example 1: Using tire size
You have a tire marked 275/70R16.
Sidewall = (275 * (70/100)) / 25.4 = 7.579 in
D = 16 + 2 * 7.579 = 31.157 in
Rev/mi = 63360 / (pi * 31.157) = 647.3
The tire makes about 647.3 revolutions per mile.
Example 2: Using overall diameter
You enter an overall tire diameter of 31.5 inches.
Rev/mi = 63360 / (pi * 31.5) = 640.3
The tire makes about 640.3 revolutions per mile.
FAQ
What does revolutions per mile mean?
Revolutions per mile means how many full turns a tire makes while traveling one mile. A smaller tire has a shorter circumference, so it turns more times per mile. A larger tire has a longer circumference, so it turns fewer times per mile.
Why is my calculated value different from a tire manufacturer spec?
The formula uses the tire’s calculated unloaded diameter. A real tire can measure differently because of tread depth, wheel width, inflation pressure, vehicle weight, and tire construction. Manufacturer rev-per-mile specs often use measured rolling circumference, so they may be slightly different.
Does changing tire size affect speedometer reading?
Yes. If you install a tire with fewer revolutions per mile than the original tire, the vehicle travels farther per wheel turn, and the speedometer may read low. If you install a tire with more revolutions per mile, the speedometer may read high.
