There are many appliances in the market place that have varying power outputs.  
To calculate with some degree of  accuracy, look for the wattage of any appliance and use the guide under ‘Watts to Amps’.

The following should only be taken as a guide.

Electric Kettle

10 amp

Toaster

3.75 amp

Travel Iron

3.45 amp

Fan heater (1kw)

4.1 amp