Data capacity and calculation of data capacity requirements

Calculating data capacity involves determining how much storage space is needed for files. You need to know the formulas for calculating sound, image, and text file sizes, and be able to convert between units.

Key points

• Sound file size = sample rate × duration × bit depth.
• Image file size = colour depth × image height × image width (pixels).
• Text file size = bits per character × number of characters.
• Exam Tip:Always check the UNITS required in the answer — you may need to convert from bits to bytes (divide by 8) or between KB, MB, GB.
• Exam Tip:Show your working clearly in calculation questions — even if the final answer is wrong, you can score method marks.
• Common Mistake:Forgetting to include ALL characters in a text file size calculation, including spaces and punctuation.