To convert from larger to smaller units: multiply. To convert from smaller to larger units: divide. 1 GB = 1,024 MB = 1,048,576 KB = 1,073,741,824 bytes (binary). Under the decimal (SI) system used by hard drive manufacturers: 1 GB = 1,000 MB = 1,000,000,000 bytes. This is why a "1 TB" drive shows ~931 GB in your operating system.
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What Is Data Storage?
Data storage refers to the capacity of a device or system to hold digital information, measured in units based on the byte — the fundamental unit of digital data. A single byte consists of 8 bits, and a bit is the most basic unit: a 0 or 1. Everything stored on a computer, phone, or server — documents, photos, videos, apps, databases — is ultimately measured in bytes and its multiples.
As file sizes and storage capacities grew, larger units were introduced: kilobytes (KB), megabytes (MB), gigabytes (GB), terabytes (TB), petabytes (PB), and beyond. Each step represents a factor of either 1,000 (decimal, used by storage manufacturers) or 1,024 (binary, used by operating systems), which is the source of a common confusion: a hard drive labeled "1 TB" by the manufacturer shows approximately 931 GB when formatted and read by your operating system.
Understanding data storage units matters in practical contexts: buying a hard drive or SSD and knowing how much usable space you will actually get, comparing cloud storage plans, estimating how many photos or videos fit on a memory card, calculating database sizes, and planning backup storage requirements.
The data storage converter handles all unit conversions instantly — from bits to exabytes — in both binary (base-2) and decimal (base-10) definitions, so you always get the right answer for your specific use case.
Storage Unit Hierarchy (Binary)
| Unit | Symbol | Binary Value | Bytes | |------|--------|------------|-------| | Bit | b | 1/8 byte | 0.125 | | Byte | B | 8 bits | 1 | | Kilobyte | KB | 2¹⁰ bytes | 1,024 | | Megabyte | MB | 2²⁰ bytes | 1,048,576 | | Gigabyte | GB | 2³⁰ bytes | 1,073,741,824 | | Terabyte | TB | 2⁴⁰ bytes | 1,099,511,627,776 | | Petabyte | PB | 2⁵⁰ bytes | ~1.13 quadrillion | | Exabyte | EB | 2⁶⁰ bytes | ~1.15 quintillion |
Binary vs. Decimal Storage Units
This is the source of one of the most common consumer confusions in technology:
Operating systems (Windows, Linux, macOS historically) use binary:
- 1 KB = 1,024 bytes
- 1 MB = 1,024 KB = 1,048,576 bytes
- 1 GB = 1,024 MB = 1,073,741,824 bytes
Hard drive manufacturers use decimal (SI):
- 1 KB = 1,000 bytes
- 1 MB = 1,000 KB = 1,000,000 bytes
- 1 GB = 1,000 MB = 1,000,000,000 bytes
A 1 TB hard drive (decimal): 1,000,000,000,000 bytes That divided by 1,073,741,824 (binary GB) = 931.3 GB as shown by your OS.
The IEC introduced "gibibyte" (GiB), "mebibyte" (MiB) etc. for binary units, but these terms are rarely used outside technical documentation.
File Size Reference
| File Type | Typical Size | |-----------|------------| | Text document (1 page) | 50–100 KB | | High-res photo (JPEG) | 2–5 MB | | RAW photo | 20–45 MB | | MP3 song (3 min, 128kbps) | ~3 MB | | HD video (1 hr, 1080p) | 4–8 GB | | 4K video (1 hr) | 15–50 GB | | Video game | 20–150 GB | | OS (Windows 11) | ~20 GB installed |
Storage Capacity Reference
| Storage Device | Typical Capacity | Common Use | |----------------|----------------|-----------| | USB flash drive | 16 GB – 256 GB | Documents, photos | | SD card (phone/camera) | 64 GB – 1 TB | Media storage | | SSD (laptop) | 256 GB – 2 TB | OS + applications | | HDD (desktop) | 1 TB – 20 TB | Mass storage, backups | | Cloud storage (free) | 5–15 GB | Google, iCloud, OneDrive |
Data Transfer Speed Context
Storage size and data transfer speed both use bits/bytes but at different scales:
- Storage: measured in bytes (MB, GB, TB)
- Transfer speed: measured in bits per second (Mbps, Gbps)
- 1 byte = 8 bits
At 100 Mbps internet connection: 100 Mbps ÷ 8 = 12.5 MB/s actual download speed. Downloading a 5 GB game: 5,000 MB ÷ 12.5 MB/s = 400 seconds ≈ 6.7 minutes.
Frequently Asked Questions
Why does my 1 TB hard drive only show 931 GB of space? Hard drive manufacturers advertise capacity using decimal (SI) units where 1 TB = 1,000,000,000,000 bytes. Your operating system shows space in binary units where 1 GiB = 1,073,741,824 bytes. 1,000,000,000,000 ÷ 1,073,741,824 = 931.3 GB. No storage is being hidden — it's a genuine unit definition difference. The discrepancy is: 0% at 1 MB, 2.4% at 1 GB, 7.4% at 1 TB, 9.1% at 1 PB.
What is the difference between bits and bytes in internet speed? Internet speeds (Mbps, Gbps) are measured in megabits/gigabits per second. File sizes are in megabytes/gigabytes. To avoid confusion, internet providers show Mbps (lowercase b = bits) while storage shows MB (uppercase B = bytes). To convert speed to file download rate: divide Mbps by 8. A 25 Mbps connection downloads at 3.125 MB/s (megabytes per second). Many consumers confuse why a "25 Mbps" connection downloads a 250 MB file in ~80 seconds rather than 10 seconds.
How much storage do I need for photos? A 12-megapixel smartphone camera produces JPEGs of approximately 3–5 MB each. At 4 MB average: 1 GB holds ~250 photos; 64 GB holds ~16,000 photos; 256 GB holds ~64,000 photos. RAW files from DSLRs run 20–45 MB each — 1 TB holds approximately 25,000–50,000 RAW files. Video is the real storage consumer: 4K at 30fps consumes ~1.5–3 GB per minute of footage.
How much data does streaming video use? Netflix standard definition: ~1 GB/hour. HD (1080p): ~3 GB/hour. 4K Ultra HD: ~7 GB/hour. YouTube HD: ~1.5 GB/hour. Streaming 4K movies 3 hours/day uses approximately 21 GB/day = 630 GB/month — approaching or exceeding many ISP data caps.
What is the largest storage unit? Beyond exabytes: zettabyte (ZB) = 10²¹ bytes = 1,000 EB. Yottabyte (YB) = 10²⁴ bytes. The entire internet's data as of 2025 is estimated at approximately 100–200 ZB (zettabytes). The human brain's storage capacity is estimated at ~2.5 petabytes. A single DNA molecule can store approximately 215 petabytes per gram — researchers are exploring DNA data storage as an ultimate high-density archival medium.
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Convert Storage Units Now
The free Data Storage Converter at RoughTools converts between bits, bytes, KB, MB, GB, TB, PB with both binary and decimal definitions. See download time estimator for any file size. No account needed, completely free.