1. What is a Gear Ratio To 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 and mechanics determine the relationship between engine speed and vehicle speed for different gear ratios.

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 inches to miles and hours to minutes)

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

3. Importance of Gear Ratio Calculations

Details: Proper gear ratio selection affects acceleration, top speed, fuel efficiency, and engine longevity. This calculation helps optimize these factors.

4. Using the Calculator

Tips: Enter the engine RPM, tire diameter in inches, and gear ratio. All values must be > 0. Typical gear ratios range from 2.5 to 4.5 for most vehicles.

5. Frequently Asked Questions (FAQ)

Q1: 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.

Q2: What's a typical gear ratio?
A: Most passenger cars have final drive ratios between 3.0 and 4.0, while trucks might use 3.5 to 4.5 for better towing.

Q3: Does this account for transmission gear ratios?
A: No, this calculates final speed based on the overall gear ratio (transmission gear × final drive ratio).

Q4: Why 1056 in the formula?
A: This combines conversion from inches to miles (63360) and minutes to hours (60): 63360/60 = 1056.

Q5: How accurate is this calculation?
A: It provides theoretical speed. Actual speed may vary due to tire slip, transmission efficiency, and other factors.