The easiest way to start to calibrate any spreader is to first set the spreader to the required setting, found by using the grams per square meter required and granular size and referring to the instruction manual for the individual spreader. If this is not available start with the middle setting. Mark out a square meter, for example on a driveway or in a garage, but not on the lawn (putting down a sheet of polythene or card to mark your square meter out makes things easier).
   Walk over the marked area with the hopper gate open at your natural walking speed. Walk to the side of the marked area if using a spinning disc. Sweep up the fertiliser within your square meter and weigh it.

   Hopefully, you should have the required grams needed. If not adjust your spreader accordingly, either to drop more, or less. Try to be as accurate as possible, but a tolerance of 5 grams either way is ok.
   To get best results, and a good even spread, it is advisable to go over your lawn twice in different directions. Where you are looking to apply 35 grams per square metre, use a setting that applies 18 grams a square metre, and make two passes over your lawn. One pass up and down, and the other from side to side. This will apply 36 grams evenly and also avoid striping.