It is a fairly easy task measuring a drum head on an acoustic drum set. There are certain steps that need to be followed in a certain order, and there is a small level of work involved.
Use a drum key (usually included with a drum set or can be purchased at a music store) and loosen the lug screws on the top of the drum. The lug screws are usually rounded at the top, and the drum key will fit snugly along the top of the lug screw.
When all of the lug screws have been loosened, remove the metal hoop and the old drum head from the drum. This will leave you with just the shell of the drum.
Next, using a tape measure, measure the diameter of the drum shell from the outside of the shell. This distance will give you the exact measurement of the new drum head you will need as a replacement. For example, if the bass drum measures 22 inches, you will need a 22-inch drum head.
Once a drum head has been purchased, place the head on the shell and replace the metal hoop on the top. The drum head may appear slightly bigger than the shell; this is normal, and will tighten down as the steps are completed.
Moving along the metal hoop, hand tighten the lug screws around the drum until they are finger tight. This will keep the drum head in place.
To complete the process, take the drum key and carefully tighten the lug screws. It is important to tighten no more than a full turn. This can cause an uneven surface for playing, and can change the tone of the drum. While carefully tightening the lug screws, use a star-pattern; do not go directly around the hoop when tightening, instead tighten one lug screw then moving to the lug screw directly across the drum. Using the drum key, tighten or loosen the lug screws along the metal hoop to tune the drum to the desired tone. Use the same star-pattern when tuning as was used when securing the drum head.
The above steps can also be applied to hand drums. The tool, however, is typically a wrench instead of a drum key. More often than not, the correct size wrench is included with the purchase of a hand drum, thus eliminating the need to find and/or purchase the necessary wrench.
Use care when measuring the diameter of the drum so as not to scratch or damage the drum When tightening the lug screws with the drum key, turn each screw the exact number of turns Give the drum head time to settle onto the drum before playing, usually 24 hours is long enough.
Make sure to measure the drum with the metal hoop and old drum head removed; if you don't, this could lead to an inaccurate measurement. Tighten the lug screws just to the point where it is fairly difficult to turn the drum key; however, it is vital to not over-tighten the lug screws.