 The width of the cut blade is measured in centimetres and the size you require will depend on how big your lawn is. For lawn sizes that are up to 50 square metres, a 30 centimetre cutting width is suitable. Up to 150 square metres, you should choose a 35 to 40 centimetre cutting width. And for lawns larger than 250 square metres, look for a petrol lawn mower with a cutting width of 46 centimetres or more. Choosing the right blade width helps you get your lawn cut in no time.