1. What is the RPM to MPH Formula?

The RPM to MPH formula calculates vehicle speed based on engine revolutions per minute (RPM), tire diameter, and gear ratio. This is useful for automotive enthusiasts, mechanics, and engineers to understand vehicle performance characteristics.

2. How Does the Calculator Work?

The calculator uses the RPM to MPH formula:

Where:

• \( rpm \) — Engine revolutions per minute
• \( tire\_diameter\_inches \) — Tire diameter in inches
• \( \pi \) — Mathematical constant (3.1416)
• \( gear\_ratio \) — Transmission gear ratio (dimensionless)
• 336 — Conversion factor combining unit conversions

Explanation: The formula converts rotational speed (RPM) to linear speed (MPH) accounting for tire circumference and gear reduction.

3. Importance of RPM to MPH Calculation

Details: This calculation helps in gear ratio selection, performance tuning, fuel efficiency analysis, and verifying speedometer accuracy.

4. Using the Calculator

Tips: Enter RPM (typically 1000-7000 for most vehicles), tire diameter (measured or from manufacturer specs), and gear ratio (including final drive ratio). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter?
A: Measure from ground to top of tire (loaded) or calculate from tire size markings (e.g., 225/45R17 has ~25" diameter).

Q2: What's a typical gear ratio?
A: Varies by vehicle - common final drive ratios range from 2.73 to 4.10 for passenger vehicles.

Q3: Why does the formula use 336?
A: This constant combines unit conversions (inches to miles, minutes to hours) and accounts for pi.

Q4: How accurate is this calculation?
A: Very accurate for theoretical speed, but actual speed may vary due to tire slippage, wear, or inflation.

Q5: Can I use this for different speed units?
A: Yes, with appropriate conversion factors (e.g., use 2652.6 for km/h instead of 336 for mph).