Grasses need to be taken care of, our lawns need to be kept neat and tidy, this is why a mower is need. A good lawn mower set at the proper height will not only make your lawn neat, it will cut the grass the proper way. That is ensuring that they remain healthy and fresh.
You see some mowers cuts the grasses from their roots thereby killing them, obviously a lot also depend on the settings, that is why a good lawn mower and the proper setting are the key. 
Actual height of cut and what the mower is adjusted to off of level smooth concrete is always going to differ, but standard is to set and measure on level concrete.
Proper mowing setting also depend on the time of season, different settings for different seasons.
1. For example during the months of May you should mow at 4 inches till October, then adjust to 3.5 inches in April, October and 3 in in November.
Every lawn is different, but that is the normal general recommended settings experts agree on.
Some mowers may not work with the above settings for mowing, example a typical John Deere, if you set it at three inches…It measures exactly three inches from the bottom of the mower deck (front)to the ground (flat smooth surface). This is because JD’s decks have a raised lip in the front.
The blades, but they were a little shorter than three inches. Contrary to popular opinion it’s not “setting the blades at X-inches, but rather” setting the deck.”
2. Yet again the above settings may not work for your Mower, although this is highly unlikely. But then hurts in being sure, so here is a third way of making sure your lawn mower is set the right way.
3. To measure true cutting height vs bench height that is the height the machine is set at there are relatively inexpensive optical prisms meant for just this use.
Companies use them to set their mower for golf fields and many other things that requires mowing.
There is also the tape measure process as to accurately determine height of cut, the major con of this is you need to take several readings across several points on the turf site then average them together, a lot of work considering that you’re still yet to get down to the business of the day, mowing.
The best part about the prism is the magnifying portion which really allows you the opportunity to see what shape the leaf tissue is in following mowing.
