RPM Vs MPH Calculator

Speed Formula:

\[ S = \frac{RPM \times TD}{GR \times 336} \]

Speed (mph):

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1. What is an RPM Vs MPH Calculator?

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

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:

\[ S = \frac{RPM \times TD}{GR \times 336} \]

Where:

\( S \) — Speed (miles per hour)
\( RPM \) — Engine revolutions per minute
\( TD \) — Tire diameter (inches)
\( GR \) — Gear ratio (unitless)
336 — Constant that combines unit conversions

Explanation: The formula converts rotational speed to linear speed while accounting for gear reduction and tire size.

3. Importance of RPM to MPH Calculation

Details: Understanding this relationship helps with gear selection, performance tuning, and fuel efficiency optimization.

4. Using the Calculator

Tips: Enter the engine RPM, tire diameter in inches, and gear ratio. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Where does the 336 constant come from?
A: It combines unit conversions (5280 feet/mile, 12 inches/foot, 60 minutes/hour) and π (pi).

Q2: How do I measure tire diameter?
A: Measure from the ground to the top of the tire (loaded radius) and multiply by 2, or use manufacturer specifications.

Q3: What gear ratio should I use?
A: Use your final drive ratio (differential ratio) multiplied by transmission gear ratio for the current gear.

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

Q5: Can I use this for different units?
A: This formula is specifically for RPM, inches, and mph. Different constants are needed for other units.