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Why is it that storage devices have less space than what they claim? (a 32GB iPod touch has 28.5GB of useble space)

Dr. Aris Thorne
Dr. Aris Thorne
Senior Science Editor · Jan 18, 2026 · Updated Apr 13, 2026

There are two ways of measuring the popular SI prefixes Giga- and Mega-. One way is using base 10. In this way, Mega- would be 10^6, and Giga- would be 10^9.

77
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1 min
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The Short Answer

There are two ways of measuring the popular SI prefixes Giga- and Mega-. One way is using base 10. In this way, Mega- would be 10^6, and Giga- would be 10^9. The other way is using base 2. Using this, Mega- would be 2^20, and Giga would be 2^30. The problem is, that the base 10 versions don't equal the base 2 versions. In fact, the Giga- (base 10) is about 7% smaller than the Giga (base 2). Obviously, device manufacturers use the base 2 version, since it's larger.

Analysis

Key Concepts: Base, giga-, mega-

This explanation focuses on base, giga-, mega- and spans 77 words across 8 sentences. The depth is typical for Space & Astronomy questions (category average: 68 words), striking a balance between accessibility and completeness.

What This Answer Covers

The explanation opens with: “There are two ways of measuring the popular SI prefixes Giga- and Mega-.” It then elaboratesultimately building toward a complete picture across 8 connected points.

How This Compares in Space & Astronomy

Ranked #180 of 500 Space & Astronomy questions by answer depth (top 37%). This falls in the detailed tier — above average depth. The explanation goes beyond surface-level but keeps things accessible.

Frequently Asked Questions

Is there a simple explanation for why it that storage devices have less space than what they claim? (a 32gb ipod touch has 28.5gb of useble space)?

There are two ways of measuring the popular SI prefixes Giga- and Mega-. One way is using base 10. In this way, Mega- would be 10^6, and Giga- would be 10^9. The other way is using base 2. Using this, Mega- would be 2^20, and Giga would be 2^30. The…

How detailed is this explanation compared to similar Space & Astronomy questions?

This is an above-average answer at 77 words, ranked #180 of 500 Space & Astronomy questions by depth. The key concepts covered are base, giga-, mega-.

What approach does this answer take to explain it that storage devices have less space than what they claim?

The explanation uses direct explanation across 77 words. It is categorized under Space & Astronomy and addresses the question through 1 analytical lens.