Need to know how many fire extinguishers your property or building needs? then use our easy to use on line fire extinguisher calculator, simply enter your building size and it will provide you with the results and options of your fire extinguisher requirements. Total surface area of site (square meters, e.g. 200) The total surface area of your site is needed in square meters M(2) for the calculations. Please note that the results of the calculations will vary depending on the types of fire extinguishers, as a result and to conform to British standard and minimal legal guidelines you would need to round up the figures to the highest numerical point, e.g. if the result produces a number of 8.6 - 9 litre water fire extinguishers are required then simply round this up to 9 x 9 litre water fire extinguishers. Do you find this calculator helpful? please feel free to share.