Pulley Ratio And RPM Calculator

Pulley Ratio and RPM Formulas:

\[ Ratio = \frac{D2}{D1} \] \[ RPM2 = \frac{RPM1}{Ratio} \]

Pulley Ratio:

Output RPM (RPM2):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is a Pulley Ratio And RPM Calculator?

Definition: This calculator determines the speed ratio between two pulleys and the resulting RPM of the driven pulley based on their diameters and input RPM.

Purpose: It helps mechanical engineers, technicians, and DIY enthusiasts properly size pulleys and calculate speed changes in belt-driven systems.

2. How Does the Calculator Work?

The calculator uses the formulas:

\[ Ratio = \frac{D2}{D1} \] \[ RPM2 = \frac{RPM1}{Ratio} \]

Where:

\( Ratio \) — Speed ratio (unitless)
\( RPM1 \) — Input RPM (revolutions per minute)
\( RPM2 \) — Output RPM (revolutions per minute)
\( D1 \) — Drive pulley diameter (inches)
\( D2 \) — Driven pulley diameter (inches)

Explanation: The ratio is determined by dividing the driven pulley diameter by the drive pulley diameter. The output RPM is then calculated by dividing the input RPM by this ratio.

3. Importance of Pulley Ratio Calculation

Details: Proper pulley sizing ensures optimal power transmission, prevents belt slippage, and achieves desired speed reduction or increase in mechanical systems.

4. Using the Calculator

Tips: Enter the input RPM, drive pulley diameter, and driven pulley diameter. All values must be > 0. The calculator will output the ratio and resulting RPM.

5. Frequently Asked Questions (FAQ)

Q1: What if I want to increase speed rather than reduce it?
A: Simply make the drive pulley (D1) larger than the driven pulley (D2) - this will result in RPM2 being higher than RPM1.

Q2: Does belt thickness affect the calculation?
A: For precision, measure pulley diameter at the belt's pitch line, but for most applications, using the outer diameter is sufficient.

Q3: Can I use this for multiple pulley systems?
A: For multiple pulleys, calculate each stage sequentially, using the output RPM from one stage as the input for the next.

Q4: What's a typical pulley ratio range?
A: Common ratios range from 1:1 to 6:1, but specialized applications may go beyond this range.

Q5: How does this relate to torque?
A: When RPM decreases, torque increases proportionally (and vice versa), assuming 100% efficiency in the system.