How do you find the current draw of an electrical circuit if you do not know the voltage and wattage of the device?

Basically if you know the Voltage supply and the power used by an appliance then you use the formula for power which is Power = Volts x Amps.

Rearrange so Amps (current) = Power / Volts

If power was 2400 Watts and Volts was 240 the Current would be 2400 / 240 = 10 Amps