1. What is an RPM to MPH Conversion Calculator?

Definition: This calculator converts rotational speed (RPM) to linear speed (MPH) based on tire diameter.

Purpose: It helps automotive enthusiasts, engineers, and mechanics determine vehicle speed from engine RPM and tire size.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Revolutions per minute
• \( TD \) — Tire diameter (inches)
• 336 — Conversion constant (combines unit conversions for inches to miles and minutes to hours)

Explanation: The formula calculates how much distance the vehicle covers per minute based on tire rotations, then converts to miles per hour.

3. Importance of RPM to MPH Conversion

Details: This conversion is essential for gear ratio calculations, speedometer calibration, and performance tuning.

4. Using the Calculator

Tips: Enter the engine RPM and tire diameter in inches. For accurate results, measure the actual loaded tire diameter rather than using the nominal size.

5. Frequently Asked Questions (FAQ)

Q1: Why is the constant 336 used?
A: It combines the conversions from inches to miles (63360) and minutes to hours (60), where 63360/60 = 1056, and accounts for π (3.1416) in circumference calculation (1056/π ≈ 336).

Q2: How do I measure tire diameter accurately?
A: Measure from the ground to the center of the wheel and multiply by 2, or mark the tire, roll one revolution, and measure the distance traveled divided by π.

Q3: Does this account for tire slippage or deformation?
A: No, this is a theoretical calculation. Actual speed may vary due to tire slip, wear, or load conditions.

Q4: Can I use this for different wheel sizes?
A: Yes, as long as you input the correct tire diameter for each wheel configuration.

Q5: How does gear ratio affect this calculation?
A: The RPM input should be the wheel RPM, not engine RPM. For engine RPM, divide by the overall gear ratio (transmission × differential).