The most widely used and quick method to obtain an indication of the construction cost of a building is by the rate/ m²-on-plan method. This is often also referred to as the ‘order of magnitude’ method of cost estimation. It certainly is both quick and convenient, but it can be very misleading if used indiscriminately and without taking care when calculating the construction area and selecting the rate. Cost comparisons of various buildings are often made by comparing the individual rates/m² without due consideration of a number of factors that can affect the rate/m² to a substantial degree. Very often the cost of a building is expressed in rate/m² and the unit cost is ignored, if calculated at all. This rate/m² is then used as the sole yardstick for the building costs