Angular Velocity Calculator
Rotational speed shows up in three units that mean the same thing: revolutions per minute, radians per second and degrees per second. Enter a value in RPM or rad/s and this calculator returns all three at once, carried to nine decimal places for precision. Add the radius of the spinning part and it also gives the tangential speed, the linear speed of a point on the rim.
How to use the angular velocity calculator
- Set the 'Input as' menu to RPM or rad/s depending on the value you have.
- Type the rotational speed into the numeric field next to that unit label.
- Optionally enter a radius in metres in the Radius (optional) field for linear speed.
- Read the RPM, rad/s, deg/s and tangential speed cards, with your input unit highlighted.
- Click Copy to grab all four results as a labelled block of text.
Examples
Convert 60 RPM
Input as RPM, value = 60, radius blank
60 rpm, 6.283185307 rad/s, 360 deg/s, tangential speed unavailable
60 RPM on a 0.5 m radius
Input as RPM, value = 60, radius = 0.5 m
60 rpm, 6.283185307 rad/s, 360 deg/s, tangential speed 3.141592654 m/s
Start from rad/s with a 3 m radius
Input as rad/s, value = 2, radius = 3 m
19.098593171 rpm, 2 rad/s, 114.591559026 deg/s, tangential speed 6 m/s
Frequently asked questions
How do I convert RPM to rad/s?
Multiply RPM by 2 x pi and divide by 60, because one revolution is 2 x pi radians and one minute is 60 seconds. So 60 RPM equals 2 x pi, which the tool shows as 6.283185307 rad/s.
How do I convert rad/s to deg/s?
Multiply the angular velocity in rad/s by 180 and divide by pi, since a full circle is 2 x pi radians or 360 degrees. At 2 rad/s that gives 114.591559026 deg/s.
Can I enter radians per second instead of RPM?
Yes. Switch the 'Input as' menu to rad/s and type your value. The tool then works backwards to RPM using rad/s times 60 divided by 2 x pi, and fills in deg/s and tangential speed as well.
What is tangential speed and why is a radius needed?
Tangential speed is how fast a point on the rim travels along its circular path, in metres per second. It equals the angular velocity in rad/s times the radius, so without a radius the linear speed is undefined and the tool shows a dash.
Why does the same spin give a bigger linear speed at a larger radius?
Every point completes a rotation in the same time, but a point farther from the axis travels a longer circle in that time. Doubling the radius doubles the distance covered per turn, so tangential speed rises in direct proportion to the radius.
How precise are the results?
Values are rounded to nine decimal places, so conversions involving pi show many digits, such as 6.283185307 rad/s for 60 RPM. This keeps round-trip conversions accurate rather than truncating to a couple of digits.
What units does the radius use?
The radius is in metres, so the tangential speed comes out in metres per second. For a radius given in centimetres or inches, convert it to metres first, for example divide centimetres by 100.
What if I enter zero or a negative number?
The tool requires values greater than zero for the speed and, when supplied, the radius. Zero or negative entries produce a short message asking for a positive number rather than a result.
Is my input sent anywhere?
No. Every conversion is computed in your browser with no network request, so the numbers you type are never uploaded or stored.
Learn more
- RPM, rad/s and deg/s: three ways to measure rotation
What revolutions per minute, radians per second and degrees per second each measure, how they convert, and when to use which.
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