Compare RPM for up to 4 different tire sizes at a given speed. Side-by-side comparison table.
The RPM Comparator is a multi-simulation tool that allows for the simultaneous side-by-side analysis of various tire size alternatives from the perspective of engine speed. It provides a clear view of how different tire sizes affect engine workload at the same driving speed, offering crucial information for selecting tires that best match your driving goals—whether it's fuel efficiency or raw performance.
The system performs real-time parallel calculations for up to four tire specifications. It derives revolutions per minute by dividing the driving speed by each tire's circumference, then combines this with final drive ratios to calculate the engine's output shaft speed. Results are presented in intuitive comparison charts and precise numerical tables, making the cumulative impact of subtle size differences on engine durability and fuel costs over long distances easy to visualize and understand.
Enter up to 4 tire sizes and set a driving speed to compare RPM across all sizes simultaneously.
Larger diameter tires result in lower RPM at the same speed, which can improve fuel economy on highways.
Use this tool to compare multiple tire options and find the best size for your driving needs.
Wheel RPM follows RPM = (kmh × 1,000,000) / (circumferenceMm × 60). Worked example: a 225/45R17 has a 634.3 mm diameter and 634.3 × π ≈ 1,992.7 mm circumference, so at 100 km/h it turns (100 × 1,000,000) / (1,992.7 × 60) ≈ 836 RPM at the wheel. Multiply by the overall drivetrain ratio to reach engine RPM.
When comparing candidates, hold speed constant and only the circumference term changes, so the wheel-RPM ratio between two tires is simply the inverse of their circumference ratio. A common error is comparing tires at different assumed speeds; always normalize to one speed first. Note that engine RPM also depends on transmission and final-drive ratios, so two tires with identical circumference produce identical wheel RPM but the engine figure shifts with the gear selected.
For accuracy, use loaded rolling circumference rather than the geometric value: tire makers publish 'revolutions per mile/km' that already account for ~3% deflection, and these differ from the calculated nominal figure. As tread wears from a new ~8 mm depth to the 1.6 mm limit, diameter drops roughly 13 mm and wheel RPM at a fixed speed rises about 1%, a small but measurable drift over a tire's life.