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ファイルサイズ換算

ファイルサイズを換算（MB、GB…）

ブラウザで動作 · アップロード不要

このツールとページ内の説明は、現在は英語のみです。動作は同じで、すべてブラウザ内で実行されます。

– bytes

Decimal (1 kB = 1,000 bytes)

Binary (1 KiB = 1,024 bytes)

Bits

How long to download or upload?

– at full speed; real transfers are usually 10–20% slower

Why does a 500 GB drive show as 465 GB? Drive makers count 1 GB as 1,000,000,000 bytes; Windows divides by 1,073,741,824 (a GiB) but still writes "GB". macOS, iOS and Android use decimal units.

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How to convert a file size

  1. Enter the size and choose its unit.
  2. Read it in every other unit, decimal and binary.
  3. Enter your connection speed to see the transfer time.

Decimal or binary?

  • Decimal units (kB, MB, GB) count in thousands: 1 GB = 1,000,000,000 bytes. Disk makers, macOS, phones and most websites use them.
  • Binary units (KiB, MiB, GiB) count in 1,024s: 1 GiB = 1,073,741,824 bytes. Windows and memory sizes use them, though Windows writes "GB".
  • Network speeds are in bits: 100 Mbit/s moves 12.5 MB per second.

よくある質問

Why does my 1 TB drive show as 931 GB?

Because 1,000,000,000,000 bytes divided by 1,073,741,824 is about 931. Windows shows binary gigabytes but labels them GB.

Is anything sent anywhere?

No. The math runs in your browser.