Nkomaha, If you are building a table saw, there will be numerous considerations needed before you can determine the necessary horsepower for the motor. If you are on the metric system, you might choose a motor that is rated in Newton-Meters, and if this is your case you will need to scour the Internet for a conversion factor. One horsepower is equal to 550 foot pounds per second. Be cautious, though; because some horsepower ratings do not accurately parallel torque - because of the rating system used. As an example, some horsepower ratings are based on an RPM that is unlikely to ever be achieved when the tool is in use.
Even when you have determined a motor to be ideal, kerf width is another factor. Narrow kerfs typically require less energy to cut through a piece of wood - but are also dependant upon proper alignment to reduce drag on the back of a blade. Not knowing your qualifications causes me to say: DO YOUR HOMEWORK - you do not want to be building something that could lead to a disaster! BE SAFE by BEING SMART! GOOD LUCK!
OPG3 Tweak everything!