How to Calculate Areal Density
Areal density is a measurement that applies to the storage available on a disk or in a disk drive. This measurement is calculated by multiplying the tracks per inch of the platter, or the portion of the disk where information is stored, by the linear density of the platter. The higher your final result, the more information can be stored on the disk. This number is represented in gigabits, a unit of measurement for computer memory.
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Instructions
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Measure the radius of the platter being used. You can determine the radius by measuring from the center of the platter, or any circle, to the outer edge. For example, the platter may have a radius of 2.1 inches.
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2
Determine the number of tracks per inch on the platter. Start with the total number of tracks on the platter which can be found in the disk manual or by contacting the manufacturer. After learning the total number of tracks, you can convert to the number of tracks per inch. For example, if the 2.1 inch platter has 30,000 tracks, then one inch of the platter would have 14,285 tracks. The formula for determining this amount is to divide the amount of tracks by the radius of the platter. 30,000 divided 2.1 is equal to 14285.
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3
Write down the maximum linear density of the disk platter. This number refers to how much information can be stored on one inch of track. For example, the linear density may be 150,000 bits per inch. You can obtain this number from the disk manufacturer.
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4
Multiply the tracks per inch by the linear density. Using the information above, you multiply 14,285 tracks per inch or TPI by 150,000 bits per inch or BPI. The result is 2,142,750,000 bits per square inch or bits/in^2.
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Convert the bits to gigabits by dividing your result by one billion. Dividing 2,142,750,000 by a billion yields 2.14275 gigabits.
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Write out your final answer, which will be the areal density of the platter. For example, the final answer to the information used above is 2.14275 gigabits/in^2.
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