Bytes, MB, GB & TB
Last reviewed: May 2026
Convert between data storage units from bytes to petabytes. The most common confusion is between decimal (SI) and binary (IEC) units — this is why your 1 TB hard drive shows only 931 GB in your operating system. Understanding this distinction prevents the frustrating feeling of "missing" storage.1
| Unit | Decimal (SI) | Binary (IEC) |
|---|---|---|
| Kilobyte / Kibibyte | 1 KB = 1,000 B | 1 KiB = 1,024 B |
| Megabyte / Mebibyte | 1 MB = 1,000,000 B | 1 MiB = 1,048,576 B |
| Gigabyte / Gibibyte | 1 GB = 10⁹ B | 1 GiB = 1,073,741,824 B |
| Terabyte / Tebibyte | 1 TB = 10¹² B | 1 TiB = 1,099,511,627,776 B |
| Content Type | Typical Size | Per 1 GB |
|---|---|---|
| Text document | 50–500 KB | 2,000–20,000 |
| MP3 song (4 min) | 3–5 MB | 200–333 |
| Phone photo | 3–5 MB | 200–333 |
| HD video (1 min) | 100–200 MB | 5–10 minutes |
| 4K video (1 min) | 300–500 MB | 2–3 minutes |
The most common source of confusion in data storage is the discrepancy between decimal (SI) and binary (IEC) units. Storage manufacturers use decimal prefixes where 1 GB equals exactly 1,000,000,000 bytes, while operating systems measure in binary units where 1 GiB equals 1,073,741,824 bytes. This 7.37% difference compounds at each level — a 1 TB drive (1,000,000,000,000 bytes decimal) shows as approximately 931 GiB in your operating system. The drive is not defective or missing space; it is simply being measured in a different unit system. This discrepancy has led to multiple class-action lawsuits against drive manufacturers, though courts have generally sided with the decimal definition as the industry standard.
| Unit | Decimal (SI) | Binary (IEC) | Difference |
|---|---|---|---|
| Kilobyte / Kibibyte | 1 KB = 1,000 B | 1 KiB = 1,024 B | 2.4% |
| Megabyte / Mebibyte | 1 MB = 1,000,000 B | 1 MiB = 1,048,576 B | 4.9% |
| Gigabyte / Gibibyte | 1 GB = 10⁹ B | 1 GiB = 2³⁰ B | 7.4% |
| Terabyte / Tebibyte | 1 TB = 10¹² B | 1 TiB = 2⁴⁰ B | 10.0% |
| Petabyte / Pebibyte | 1 PB = 10¹⁵ B | 1 PiB = 2⁵⁰ B | 12.6% |
| Exabyte / Exbibyte | 1 EB = 10¹⁸ B | 1 EiB = 2⁶⁰ B | 15.3% |
| File Type | Typical Size | Per 1 GB | Per 1 TB |
|---|---|---|---|
| Text email | 10–50 KB | ~20,000–100,000 | ~20M–100M |
| MP3 song (4 min) | 3–5 MB | ~200–333 | ~200K–333K |
| Smartphone photo | 3–8 MB | ~125–333 | ~125K–333K |
| DSLR RAW photo | 25–60 MB | ~17–40 | ~17K–40K |
| 1-hour HD video (1080p) | 3–6 GB | ~0.17–0.33 | ~167–333 |
| 1-hour 4K video | 10–30 GB | ~0.03–0.10 | ~33–100 |
| AAA video game | 50–150 GB | ~0.007–0.02 | ~7–20 |
| Full OS install | 20–40 GB | — | ~25–50 |
Different storage technologies trade off capacity, speed, durability, and cost per gigabyte. Hard disk drives (HDD) remain the cheapest option at approximately $0.015–$0.03 per GB, making them ideal for bulk storage, backups, and NAS systems. Solid-state drives (SSD) using NAND flash cost $0.05–$0.10 per GB but deliver 10–100× faster read/write speeds with no moving parts, making them the standard for operating system drives, laptops, and high-performance desktops. NVMe SSDs connected via PCIe can exceed 7,000 MB/s sequential read speeds compared to 150–250 MB/s for HDDs — a difference you feel immediately in boot times, file transfers, and application loading. Cloud storage pricing varies widely: Google Drive and OneDrive charge roughly $0.01–$0.02 per GB per month ($2.99/month for 100 GB), while enterprise cloud storage like AWS S3 runs $0.023 per GB/month for standard access and $0.004 per GB/month for infrequent access tiers.
Data transfer rates introduce an additional layer of confusion because they are measured in bits per second, not bytes per second. One byte equals 8 bits, so a 100 Mbps (megabits per second) internet connection transfers approximately 12.5 MB (megabytes) per second — one-eighth of what the number might suggest. ISPs universally advertise speeds in bits because the larger numbers look more impressive. A common broadband connection of 300 Mbps downloads at roughly 37.5 MB/s in practice, meaning a 1 GB file takes approximately 27 seconds under ideal conditions. Gigabit internet (1,000 Mbps = 1 Gbps) theoretically downloads at 125 MB/s, though real-world speeds typically reach 70–90% of the advertised rate due to protocol overhead, network congestion, and hardware limitations.
Choosing the right storage capacity depends entirely on your usage pattern. For basic computing — web browsing, email, document editing, and light photo storage — 256 GB is adequate and 512 GB is comfortable. Gamers should plan for at least 1 TB, as modern AAA titles regularly consume 50–150 GB each (Call of Duty alone has exceeded 200 GB with all packs installed). Video editors and photographers working with RAW files or 4K footage need 2–4 TB minimum, with many professionals maintaining 10+ TB of project storage. Smartphone users who capture lots of photos and videos should consider 256 GB as the minimum comfortable option — 128 GB fills quickly when shooting 4K video at 400 MB per minute. For long-term archival, external drives and cloud backups provide cost-effective solutions, but remember that hard drives have finite lifespans (typically 3–5 years for mechanical drives under continuous use) and should be replaced periodically.
→ Use decimal for purchasing, binary for OS reporting. When buying storage, manufacturers use decimal. When checking available space in your operating system, you see binary. Expect a ~7–10% apparent "loss" per TB.
→ Don't confuse bits and bytes. Internet speeds use bits (Mbps). File sizes use bytes (MB). Divide the speed in Mbps by 8 to get your actual download rate in MB/s.
→ Plan for 20% headroom. SSDs slow down significantly when filled above 80% capacity. Always leave at least 20% of your SSD free for optimal performance and drive longevity.
See also: Subnet Calculator · Binary Calculator · Unit Converter · Hex to RGB
The world's total data volume has grown exponentially — from approximately 2 zettabytes (2 trillion gigabytes) in 2010 to over 120 zettabytes in 2023, and projected to exceed 180 zettabytes by 2025. To put this in perspective, one zettabyte equals 1,000 exabytes, 1 million petabytes, or 1 billion terabytes. If you stored one zettabyte on standard Blu-ray discs, the stack would reach from Earth to the Moon approximately 23 times. This explosion is driven by video streaming (which accounts for over 60% of global internet traffic), social media uploads, IoT sensor data, cloud computing, and AI training datasets. A single autonomous vehicle generates approximately 5 TB of data per day from its cameras, lidar, and radar sensors. Understanding data storage units is increasingly important as personal data footprints grow — the average person now generates approximately 1.7 MB of data per second, creating roughly 147 GB per day through digital interactions, device usage, and online activity.
Enterprise storage systems use RAID (Redundant Array of Independent Disks) configurations that trade raw capacity for data protection. RAID 1 mirrors data across two drives, providing full redundancy at 50% usable capacity — two 1 TB drives yield only 1 TB of usable space. RAID 5 distributes parity data across three or more drives, losing one drive's worth of capacity to fault tolerance — four 1 TB drives yield 3 TB usable. RAID 6 loses two drives' capacity but can survive two simultaneous drive failures. Understanding these storage overhead calculations is essential for IT planning and explaining why a server with 10 TB of raw disk space may show only 7.5 TB of usable capacity after RAID configuration and filesystem formatting overhead.
Modern SSDs use NAND flash memory organized into pages (typically 4–16 KB) and blocks (64–512 pages). Data can be written at the page level but can only be erased at the block level — this asymmetry drives the need for wear leveling and garbage collection algorithms that manage writes to extend drive lifespan. Consumer SSDs are rated for endurance in TBW (terabytes written) — a typical 1 TB NVMe SSD is rated for 600 TBW, meaning you could write its entire capacity 600 times before exceeding the warranty specification. At typical consumer workloads of 20–40 GB of writes per day, a 600 TBW drive would last approximately 40–80 years in theory — far exceeding other failure modes. Enterprise SSDs in data centers may be rated for 3–10 DWPD (drive writes per day over a 5-year warranty), or 5,500–18,250 TBW for a 1 TB drive, reflecting much heavier write workloads.
For most consumers, the key takeaway is that SSD endurance far exceeds realistic usage — drive failures are more likely from controller electronics or firmware than from wearing out the flash cells themselves.
As data volumes continue to grow exponentially across personal devices, enterprise systems, and cloud infrastructure, fluency in data storage units and their conversions is increasingly essential for consumers and professionals alike.
→ 1 TB drive ≈ 931 GiB. The decimal vs binary gap explains 'missing' space.
→ Use MB for file estimates. Quick rule: photos ~4 MB, songs ~4 MB, HD video ~150 MB/min.
→ Cloud storage is decimal. Google, iCloud, etc. use SI (decimal) GB.
→ SSD vs HDD pricing: SSDs cost more per GB but are much faster.
See also: Percentage · Length · Weight · Scientific