RPM To Speed Formula

Speed Formula from RPM:

\[ S = \frac{RPM \times TD \times 60}{GR \times 63360} \]

Vehicle Speed (mph):

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1. What is the RPM to Speed Calculator?

Definition: This calculator estimates vehicle speed 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 tuning and performance analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ S = \frac{RPM \times TD \times 60}{GR \times 63360} \]

Where:

\( S \) — Vehicle speed (mph)
\( RPM \) — Engine revolutions per minute
\( TD \) — Tire diameter (inches)
\( GR \) — Gear ratio (unitless)
63360 — Conversion factor (inches per mile)

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

3. Importance of RPM to Speed Calculation

Details: Understanding the relationship between RPM and speed helps optimize gear ratios, improve fuel efficiency, and enhance vehicle performance.

4. Using the Calculator

Tips: Enter the engine RPM, tire diameter in inches, and gear ratio (default 3.73). All values must be > 0.

5. Frequently Asked Questions (FAQ)

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

Q2: What's included in gear ratio?
A: The overall gear ratio including transmission gear, differential ratio, and any transfer case reduction.

Q3: Why 63360 in the formula?
A: This converts inches to miles (1 mile = 63,360 inches) and minutes to hours (×60).

Q4: Does this account for tire slippage?
A: No, this calculates theoretical speed. Actual speed may vary due to tire slip, wear, or inflation.

Q5: Can I use this for different units?
A: For km/h, multiply result by 1.60934 or modify the formula with metric conversion factors.