1. What is the RPM to MPH Calculator?

Definition: This calculator estimates vehicle speed in miles per hour (mph) based on engine RPM, tire diameter, and gear ratio.

Purpose: It helps automotive enthusiasts, mechanics, and engineers determine vehicle speed at specific RPMs for gear selection and performance tuning.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( S \) — Speed (mph)
• \( RPM \) — Engine revolutions per minute
• \( TD \) — Tire diameter (inches)
• \( GR \) — Gear ratio (unitless)
• \( 1056 \) — Conversion factor (combines unit conversions)

Explanation: The formula calculates how much distance the vehicle travels per minute based on wheel rotation, then converts to miles per hour.

3. Importance of RPM to MPH Calculation

Details: Understanding this relationship helps optimize gear ratios for performance or fuel economy, verify speedometer accuracy, and plan transmission builds.

4. Using the Calculator

Tips: Enter the engine RPM, tire diameter (measured from ground to top of tire), and final drive gear ratio (including transmission gear if calculating for a specific gear).

5. Frequently Asked Questions (FAQ)

Q1: How do I measure tire diameter accurately?
A: Measure from the ground to the top of the tire with the vehicle's weight on it, or use manufacturer specs.

Q2: What's included in the gear ratio?
A: Use the final drive ratio multiplied by the transmission gear ratio for the specific gear you're calculating.

Q3: Why is 1056 the conversion factor?
A: It combines conversions from inches to miles (63360) and minutes to hours (60): 63360/60 = 1056.

Q4: Does this account for tire slippage or deformation?
A: No, this is a theoretical calculation. Actual speed may vary slightly due to tire flex, slippage, or wear.

Q5: How can I use this for gear selection?
A: Calculate speed at redline RPM with different gear ratios to find optimal gearing for your performance goals.