# How to calculate the rpm of a motor and speed reducer

Written by andrea helaine
• Share
• Tweet
• Share
• Pin
• Email

Motors run at a specific revolutions per minute (RPM) and a speed reducer is needed if you want to keep that motor, but have a lower RPM. Calculating the RPM resulting from a motor and speed reducer assembly requires only basic mathematical knowledge.

Skill level:
Easy

### Things you need

• Motor base RPM
• Speed reducer ratio

## Instructions

1. 1

Write down the rated RPM of your motor; for example, 5000 RPM.

2. 2

Write down the ratio of the speed reducer; for example, 12:5.

3. 3

Calculate the reduction by dividing 12 by 5, which equals 2.4.

4. 4

The RPM of the assembly is the RPM motor divided by the reduction. In our example, it would be 5000 RPM/2.4 = 2083 RPM.

#### Tips and warnings

• The ratio of a reducer will always be in the form of A:B, where A>B.
• The RPM found should always be lower than the base RPM of the motor. If it is not, either redo your calculation or make sure you did not get a speed multiplier instead of a reducer.

### Don't Miss

#### References

• All types
• Articles
• Slideshows
• Videos
##### Sort:
• Most relevant
• Most popular
• Most recent