Standard base cabinets are 34-1/2" high plus 1-1/2" for the counter top for a total of 36", which is also the height of a range. Standard upper cabinets are 30" high and are installed 18" above the base cabinets. Most cabinetmakers create a 6" high recess over the range by installing a 24" high cabinet over the range. Most standard hoods are 6" high.
Therefore, if you do the math, the bottom of the hood would be 18" from the top of the range. This is also the minimum clearance required by building codes in most areas in the US.
In addition to the fine first answer above, manufacturers of range hoods, both the unattached to the cabinet type and the fasten to the cabinet type, include the allowable effective heights for their particular hood. Read the instructions that come with the hood.
Many range hood manufacturers recommend 30" to 36" above the range top for effective ventilation. You may als0 want to consider the height of the end user as you want to be sure to have forehead clearance ;) don't want a bump on the head from trying to smell the sauce!