Rolling Circumference Comparator
Compare how far each tire rolls in one turn. Use the calculator below. Results update as you type.
Circumference = π × Overall DiameterHow the Rolling Circumference Comparator Works
This comparator works by comparing published or measured rolling circumferences and converting each into revs per km, revs per mile and percent difference. It uses real rolling data, not nominal math.
- Enter the reference rolling circumference, for example 2,000 mm (78.7 in).
- Enter the candidate's rolling circumference, for example 2,050 mm.
- Read the difference: +2.50%.
- Read revs per km for each: 500.0 and 487.8.
The Formula
The formula is Difference (%) = (Candidate − Reference) ÷ Reference × 100.
Difference (%) = (C_cand − C_ref) ÷ C_ref × 100 Revs per km = 1,000,000 ÷ C (mm) Revs per Mile = 1,609,344 ÷ C (mm) Circumference = π × Overall DiameterWorked example: a 1,980 mm tire against a 2,000 mm reference differs by −1.00% and turns 505.1 times per km.
Conversion Table
The conversion table compares 10 rolling circumferences with a 2,000 mm reference. Differences run from −7.50% to +10.00%.
The ±1% rows (1,980 mm and 2,020 mm) mark the limit many AWD makers set between tires on the same vehicle.
| Rolling Circ (mm) | Rolling Circ (in) | Revs / km | Revs / Mile | vs 2,000 mm |
|---|---|---|---|---|
| 1850 | 72.8 | 540.5 | 869.9 | -7.50% |
| 1900 | 74.8 | 526.3 | 847.0 | -5.00% |
| 1950 | 76.8 | 512.8 | 825.3 | -2.50% |
| 1980 | 78.0 | 505.1 | 812.8 | -1.00% |
| 2000 | 78.7 | 500.0 | 804.7 | 0.00% |
| 2020 | 79.5 | 495.0 | 796.7 | +1.00% |
| 2050 | 80.7 | 487.8 | 785.0 | +2.50% |
| 2100 | 82.7 | 476.2 | 766.4 | +5.00% |
| 2150 | 84.6 | 465.1 | 748.5 | +7.50% |
| 2200 | 86.6 | 454.5 | 731.5 | +10.00% |
What Is the Rolling Circumference Comparator?
The Rolling Circumference Comparator is a tool that compares tires using their measured rolling circumference. Rolling circumference is the distance a loaded tire travels in one turn, and tire makers publish it in data books for many sizes.
Rolling values are the most accurate inputs for speedometer and tachograph work. They already include load flattening and tread effects.
Common Uses
This comparator has 4 uses: tachograph calibration, AWD checks, speedometer setup and brand comparison.
- Calibrate tachographs: Use rolling values for legal records.
- Check AWD sets: Keep axle sets within 1%.
- Set speedometers: Enter real rolling distance in tuners.
- Compare brands: Rank real rolling sizes across makers.