# How to calculate torque for a motor?

• fkneg12

#### fkneg12

Hi all,

Just wondering how to work out what torque motor we need to get to lift a certain (as yet undetermined) weight.
Is there a formula to work out what torque we need once we know the weight?

It depends on the diameter of the drum that you are winding your cable onto. If you had a weight of 1 Kg (1 N) and a dia of 1 meter youd need a minimum torque of 1NM.

Torque is Force X Displacement. So you could calculate your force using Newtons equations of motion to get your missing variable like velocity if needed. Or you could just assume a height and multiply by gravity. that will give you force. This however is also assuming a 0 angle in the lift.

If you want to calculate torque which occurs in shafts, you have to use this formula;
P=2* (pi) * f *T
T is torque (Newton*meter)
P is power (Watt)
pi = 3,1415...
f is frequency of rotation (1/s = Hz)
sometimes you can find revolution as rpm. So you have to change rpm to frequency.
(1 Hz = 60 rpm) 