To calculate the power consumption of your home appliances, 1st you have to know the wattages of your electrical equipment.
Generally, they are written on the nameplate of the appliance. Such as the example given for a ceiling fan,

Now you have to collect all the wattages of the appliances used by your house.

Now you can calculate the total amount of power consumption in KWH for your house/ Office.

You have to multiply the amount of similar appliances by wattage and how many hours you generally use them, and divide the number by 1000.

For example, Here in the image you can see the total number of lights used is 16. Those lights each consume 15 watts of power. And the total numbers of hours they are used in a day is 8.

So, the calculation will be : (16*15*8)/1000= 1.92 KWH

Therefore you can calculate each appliance and adding them up will give you the total value of power consumption.