1. What is RPM to MPH Conversion?

Definition: This calculator converts engine RPM (revolutions per minute) to vehicle speed in miles per hour based on tire diameter.

Purpose: It helps automotive enthusiasts, mechanics, and engineers understand the relationship between engine speed and vehicle speed.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (miles per hour)
• \( RPM \) — Engine 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 far the vehicle travels per minute based on tire circumference and RPM, then converts to miles per hour.

3. Importance of RPM to MPH Conversion

Details: Understanding this relationship helps with gear ratio selection, fuel efficiency optimization, 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: Where does the 336 constant come from?
A: It combines conversion factors: (60 minutes/hour) / (12 inches/foot × 5280 feet/mile × π) ≈ 336.

Q2: Does this account for gear ratios?
A: No, this gives direct drive speed. For real-world calculations, multiply RPM by the overall gear ratio first.

Q3: How do I measure tire diameter accurately?
A: Measure from ground to top of tire with vehicle weight on it, or calculate: (wheel diameter) + 2×(sidewall height).

Q4: Why is my actual speed different from the calculation?
A: Factors like tire slippage, inflation pressure, gear ratios, and transmission slip can affect real-world speed.

Q5: Can I use this for different wheel sizes?
A: Yes, just input the actual tire diameter for each wheel size you want to compare.