当你兴冲冲地从店里买回一块标注为 1TB 的移动硬盘或 SSD，插上电脑（尤其是 Windows 系统）时，你可能会大失所望：系统显示的可用空间通常只有 931GB 左右。剩下的 70GB 去哪了？是被厂家“偷”走了吗？还是硬盘坏了？
When you excitedly buy a new 1TB external hard drive or SSD and plug it into your computer (especially a Windows PC), you might be disappointed to see that the available space is only around 931GB. Where did the missing 70GB go? Was it "stolen" by the manufacturer? Or is the drive defective?
这不是硬件故障，而是十进制（厂家用）与二进制（系统用）算法差异导致的必然结果。
This is not a hardware fault, but a natural result of the difference between Decimal (used by manufacturers) and Binary (used by OS) calculations.
1. 厂家与系统的“语言代沟” / The Language Gap
厂家的视角：十进制 (SI 标准)
对于硬盘生产商（如三星、希捷、西部数据）来说，为了计算方便和符合国际单位制（SI），他们采用以 10 为底数的算法。在他们的定义中：
- 1 KB = 1,000 Bytes
- 1 MB = 1,000,000 Bytes
- 1 GB = 1,000,000,000 Bytes
- 1 TB = 1,000,000,000,000 Bytes
Manufacturers' Perspective: Decimal (SI Standard)
For storage manufacturers (like Samsung, Seagate, Western Digital), they use the Base-10 system to align with the International System of Units (SI). In their definition:
- 1 KB = 1,000 Bytes
- 1 MB = 1,000,000 Bytes
- 1 GB = 1,000,000,000 Bytes
- 1 TB = 1,000,000,000,000 Bytes
操作系统的视角：二进制
然而，计算机底层是基于二进制（0 和 1）运行的。对于 Windows 操作系统来说，它依然沿用 2 的 10 次方（1024）作为进位标准：
- 1 KiB = 1,024 Bytes
- 1 MiB = 1,024 * 1,024 Bytes
- 1 GiB = 1,024 * 1,024 * 1,024 Bytes
Operating System's Perspective: Binary
However, computers operate on binary logic (0s and 1s). Windows still uses the Base-2 system (powers of 1024) for calculation:
- 1 KiB = 1,024 Bytes
- 1 MiB = 1,024 * 1,024 Bytes
- 1 GiB = 1,024 * 1,024 * 1,024 Bytes
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(广告：文章信息流广告)2. 数学换算：消失的 7% 去哪了？ / The Math Behind
让我们来算一笔账。当你购买 1TB 硬盘时，厂家给你的总字节数是 1,000,000,000,000 字节。
现在，我们将这些字节按 Windows 的 1024 算法进行转换：
Let's do the math. When you buy a 1TB drive, the manufacturer provides exactly 1,000,000,000,000 bytes.
Now, let's convert these bytes using the Windows 1024-based algorithm:
976,562,500 / 1024 = 953,674 MB
953,674 / 1024 ≈ 931.32 GB
这就是 931GB 的由来！容量越大，这种差距就越明显。例如，标注为 16TB 的企业级硬盘，在系统中显示可能只有 14.5TB，中间差了整整 1.5TB，这足以装下几百部高清电影。
And that’s where the 931GB comes from! The larger the capacity, the more noticeable the gap. For instance, a 16TB enterprise drive might show only 14.5TB in Windows—a massive 1.5TB difference, enough to store hundreds of HD movies.
3. 为什么不统一标准？ / Why No Unified Standard?
你可能会问，为什么不直接让厂家也用 1024？或者让 Windows 改成 1000？
其实已经有标准了。 国际电工委员会（IEC）在 1998 年就制定了标准：使用 GiB (Gibibyte) 表示 1024 进制，GB (Gigabyte) 表示 1000 进制。macOS 系统已经更新，显示 1TB 硬盘就是 1.0TB（按十进制显示），而 Windows 依然坚持使用 "GB" 这个单位名，实则进行 GiB 的运算，这才导致了用户的困惑。
You might ask: Why don't manufacturers use 1024? Or why doesn't Windows switch to 1000?
Standards actually exist. In 1998, the IEC established that GiB (Gibibyte) should represent the 1024-base, while GB (Gigabyte) represents the 1000-base. macOS has already updated to show a 1TB drive as 1.0TB (using decimal), whereas Windows continues to use the label "GB" while calculating in GiB, causing ongoing confusion.
4. 还有其他占用空间吗？ / Other Hidden Factors
除了算法差异，还有几个因素会让你可用的空间更少：
- 文件系统开销： 格式化硬盘（NTFS, exFAT）会占用一部分空间来存储文件索引。
- 隐藏分区： 品牌电脑通常会有恢复分区或引导分区。
- 预留空间： SSD 需要一部分“超额配置”空间来管理坏块和提升寿命。
Besides the algorithm gap, a few other factors can eat into your usable space:
- File System Overhead: Formatting (NTFS, exFAT) takes up space for file index tables.
- Hidden Partitions: OEM PCs often have recovery or boot partitions.
- Over-provisioning: SSDs reserve space to manage bad blocks and extend lifespan.
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(广告：文章底部相关内容推荐)总结 / Conclusion
下次你买硬盘时，记住一个简单的公式：标注容量 × 0.93 ≈ 实际 Windows 显示容量。理解了这个原理，你就不必再担心自己的硬盘被“缩水”了。为了获得最精确的计算结果，推荐收藏我们的 在线数据容量单位转换器，它能帮你一键完成所有复杂的二进制进位计算。
Next time you buy a drive, remember the rule: Labeled Capacity × 0.93 ≈ Actual Windows Capacity. Knowing this saves you from worrying about "missing" storage. For the most precise results, check out our Online Data Unit Converter to handle all complex binary calculations in one click.