IGCSE · Practice questions · Measuring data storage and calculating file sizes

Divide by 1024.

Six original Cambridge-style questions on storage units and file size calculations, with worked solutions.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Bits first, then 1024.

Ladder: bit, nibble (4 bits), byte (8 bits), then KiB, MiB, GiB, TiB, PiB, EiB, each × 1024.
Image: width × height × colour depth = bits.
Sound: sample rate × resolution × seconds = bits.
Finish: ÷ 8 for bytes, ÷ 1024 per step, and give the unit asked for.

Recall

[2 marks]

Put these units in order from smallest to largest: GiB, byte, TiB, nibble, KiB, bit, MiB.

bit, nibble, byte, KiB, MiB, GiB, TiB. ✓
(1 mark for bit, nibble, byte; 1 mark for KiB, MiB, GiB, TiB) ✓

Convert

[2 marks]

Convert (a) 6 GiB to MiB and (b) 20 480 KiB to MiB.

(a) 6 × 1024 = 6144 MiB. ✓
(b) 20 480 ÷ 1024 = 20 MiB. ✓

Calculate

[3 marks]

A photograph is 1600 pixels wide and 1200 pixels high with a colour depth of 24 bits. Calculate the file size in MiB, to 2 decimal places.

1600 × 1200 × 24 = 46 080 000 bits; ÷ 8 = 5 760 000 bytes. ✓
5 760 000 ÷ 1024 = 5625 KiB. ✓
5625 ÷ 1024 = 5.49 MiB. ✓

Calculate

[3 marks]

A 20-second sound clip is recorded with a sample rate of 44 100 Hz and a sample resolution of 16 bits. Calculate the file size in KiB, to 2 decimal places.

44 100 × 16 × 20 = 14 112 000 bits. ✓
14 112 000 ÷ 8 = 1 764 000 bytes. ✓
1 764 000 ÷ 1024 = 1722.66 KiB. ✓

Apply

[2 marks]

A camera's memory card holds 32 GiB. Each photo is 4 MiB. Calculate how many photos the card can store.

32 GiB = 32 × 1024 = 32 768 MiB. ✓
32 768 ÷ 4 = 8192 photos. ✓

Analysis

[2 marks]

A student converts 3 145 728 bytes to MiB by dividing by 1 000 000 and gets 3.15 MiB. Explain the error and give the correct answer.

1 MiB is 1024 × 1024 = 1 048 576 bytes, not 1 000 000; calculations must use 1024. ✓
3 145 728 ÷ 1 048 576 = 3 MiB. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.