Digital Storage Units Explained: Bits, Bytes, GB and TB

The Building Block: The Bit

All digital data starts with the bit — the smallest unit of information in computing. A bit is either a 0 or a 1 (binary). Eight bits make one byte, which can represent 256 different values and is enough to store a single character of text.

The Storage Unit Hierarchy

• 1 Bit (b) = a single 0 or 1
• 1 Byte (B) = 8 bits
• 1 Kilobyte (KB) = 1,024 bytes
• 1 Megabyte (MB) = 1,024 KB = 1,048,576 bytes
• 1 Gigabyte (GB) = 1,024 MB
• 1 Terabyte (TB) = 1,024 GB
• 1 Petabyte (PB) = 1,024 TB

Why 1,024 and Not 1,000?

Computers work in binary (base 2), so storage is measured in powers of 2. 2^10 = 1,024, which is close to 1,000 but not exactly. This is why 1 kilobyte = 1,024 bytes, not 1,000. Hard drive manufacturers often use 1,000 (decimal) to report capacity, which is why your new 500 GB drive might show as ~465 GB in your operating system.

Real-World Size Examples

• A text message ≈ 1–2 KB
• A high-quality photo ≈ 3–5 MB
• A 2-hour HD movie ≈ 4–8 GB
• A typical laptop hard drive = 500 GB to 2 TB
• All data on the internet ≈ several zettabytes (1 ZB = 1 billion TB)

Binary Prefixes (IEC Standard)

To eliminate confusion, the IEC introduced binary prefixes: kibibyte (KiB = 1,024 B), mebibyte (MiB = 1,024 KiB), gibibyte (GiB = 1,024 MiB). These are more precise but less commonly used in everyday language.

Convert any storage value instantly with our free digital storage converter.

Step-by-Step Conversion Examples

Why Your 1 TB Drive Shows Only 931 GB in Windows

A drive manufacturer labels a hard drive as "1 TB." That means it contains exactly 1,000,000,000,000 bytes (decimal). When Windows reads the drive, it reports in GiB (binary gibibytes), even though it labels the number "GB":

1,000,000,000,000 bytes ÷ 1,073,741,824 bytes/GiB = 931.32 GiB

The ~69 GB that appears "missing" hasn't gone anywhere — it's a labeling discrepancy between decimal (manufacturer) and binary (OS) systems. macOS Monterey and later correctly shows decimal GB, so the same drive appears as 1.00 TB. The IEC introduced the GiB prefix in 1998 (IEC 80000-13) precisely to eliminate this confusion.

Calculating Download Time from Internet Speed

Your internet connection is 100 Mbps (megabits per second). How long to download a 4 GB movie?

Step 1: Convert 4 GB to megabits: 4 GB × 1,000 MB/GB × 8 bits/byte = 32,000 Mb

Step 2: Divide by speed: 32,000 Mb ÷ 100 Mbps = 320 seconds ≈ 5.3 minutes

Key rule: bits vs. bytes — a "100 Mbps" connection downloads at 100 ÷ 8 = 12.5 MB/s. Internet speeds are always advertised in bits (lowercase b); file sizes are always in bytes (uppercase B). Confusing the two is a common source of "my internet seems slower than advertised."

Cloud Storage Planning

You have 5,000 photos averaging 8 MB each. How much cloud storage is needed?

5,000 × 8 MB = 40,000 MB = 40 GB (decimal)

In GiB (as some cloud dashboards display): 40,000,000,000 bytes ÷ 1,073,741,824 = 37.25 GiB

A 50 GB plan provides comfortable headroom. Google One's 100 GB plan holds roughly 12,500 photos at 8 MB each, plus email and document storage. Video files are far larger: a 1-minute 4K clip at 60fps can run 400–500 MB.

Source: IEC 80000-13 (binary prefixes); SI Brochure 9th edition (decimal prefixes). Last verified: May 2026.