# Calculating power from torque

so for my project im designing a Tesla turbine and have calculated that the torque it will output is 38Nm. I would like to know what more information I would need that i could calculate theoretically to calculate how much power it would output from this.

Thanks.

• This is a really basic physics question. – Olin Lathrop Dec 28 '16 at 12:55
• Power = torque * rotational speed. If using SI units, that's Nm * radians/second, giving watts. – user_1818839 Dec 28 '16 at 13:31

general power formula is 2*3.14159 * N *T

you need to know revolutions per second for finding power. there are various tachometers available. (stroboscope,aluminum cup,mechanical tachometer, etc) get the reading of revolution per min. convert it to rev per sec.

then use it in the formula p = 2*3.1415*N*(38)

• there is even a mobile app that can estimate revolutions per minute – Fennekin Dec 28 '16 at 13:01
• The 2*Pi is only an artefact of not using SI units properly. – user_1818839 Dec 28 '16 at 13:33
• gee, if you convert rpm to rad/s shouldnt there be a 60 in there someplace? – agentp Dec 28 '16 at 13:57
• If you are using rad/sec, then you don't need to divide by 60. Power is in joule per second – Fennekin Dec 28 '16 at 14:33

Power is force times speed.

If your shaft is turning at 1 Hz, for example, then the power is

(38 N)(2Π m/s) = 239 Nm/s = 239 W