KB, MB, GB, TB Explained: Why Your 1 TB Drive Shows 931 GB

Two counting systems share the same abbreviations, which is why a new drive always looks smaller than the box promised.

Decimal vs binary Drive manufacturers use decimal: 1 GB = 1,000,000,000 bytes. Windows reports binary: 1 GiB = 1,073,741,824 bytes, but labels it "GB". The gap grows with size — about 2.4% at kilobytes, 7.4% at gigabytes and 9.9% at terabytes.

The ladder 1 KB = 1,000 bytes (1 KiB = 1,024). 1 MB = 1,000 KB. 1 GB = 1,000 MB. 1 TB = 1,000 GB.

What fits 1 MB: a high-quality photo at web resolution or about 500 pages of plain text. 1 GB: roughly 250 songs, 300 phone photos, or 30 minutes of 1080p video. 1 TB: about 250,000 photos or 500 hours of HD video.

Bits vs bytes Internet speed is quoted in megabits per second, storage in megabytes. Divide Mbps by 8 for MB/s — a 100 Mbps line downloads at about 12.5 MB/s at best, so a 1 GB file takes at least 80 seconds.