Convert between bits, bytes, KB, MB, GB, TB, and PB instantly. Also converts Kilobits, Megabits, and Gigabits.
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Picking Decimal or Binary
Comparing to a purchased drive or plan
Storage manufacturers and cloud/mobile data plans quote decimal (KB/MB/GB/TB) — use these units to check whether a drive or plan matches its advertised size.
Comparing to what your OS displays
Windows, macOS, and Linux file managers typically report binary values (often still labeled GB/TB by the OS, but actually computed as GiB/TiB) — use the KiB/MiB/GiB/TiB units here to match what your computer shows you.
Network speed vs. file size
ISPs advertise connection speed in bits (Mbps, Gbps); file sizes are in bytes (MB, GB). Divide a bits-per-second speed by 8 to get bytes-per-second before comparing to a file size.
How to Use the Data Size Converter
Enter your data size value — type the number of bytes, kilobytes, megabytes, or any unit.
Select the input unit — choose from bits, bytes, kilobytes, megabytes, gigabytes, terabytes, or petabytes.
Choose binary or decimal — use KB/MB/GB/TB for the decimal (1,000-based) convention that storage manufacturers and network speeds use, or KiB/MiB/GiB/TiB for the binary (1,024-based) convention operating systems and file managers use. Both are available as separate units below.
Read all conversions — see your data size expressed in all units simultaneously.
Use for storage planning — calculate how many files fit on a drive, compare file sizes, or understand download times.
⚠️ The 1 TB hard drive confusion: Hard drive manufacturers use decimal (1 TB = 1,000,000,000,000 bytes). Your operating system uses binary (1 TiB = 1,099,511,627,776 bytes). A '1 TB' drive shows as ~931 GB in Windows/macOS. This is not a defect — it's a unit definition difference. The drive contains exactly 1,000,000,000,000 bytes; Windows just displays it in binary gigabytes.
Understanding Data Size Units
💾 Bits and Bytes
Bit: the smallest unit of digital information — 0 or 1. Byte = 8 bits: the standard unit for data storage (one ASCII character = 1 byte). All storage sizes are multiples of bytes. Network speeds are often in bits per second (Mbps, Gbps) while file sizes are in bytes (MB, GB) — causing confusion: a 100 Mbps connection transfers 100/8 = 12.5 MB per second.
📊 Binary vs Decimal
Binary (IEC standard): 1 KiB = 1,024 bytes (2¹⁰). Used by OS file systems, RAM. Decimal (SI standard): 1 KB = 1,000 bytes (10³). Used by storage manufacturers, network speeds. For small files, difference is negligible. For large drives: 1 TB (decimal) = 0.909 TiB (binary) — explaining why a 1 TB drive shows as ~931 GB in Windows.
🔢 Size Scale
1 Byte = 8 bits. 1 KB ≈ 1 thousand bytes. 1 MB ≈ 1 million bytes. 1 GB ≈ 1 billion bytes. 1 TB ≈ 1 trillion bytes. 1 PB ≈ 1 quadrillion bytes. 1 EB ≈ 1 quintillion bytes. 1 ZB ≈ 1 sextillion bytes. Global internet traffic now measured in zettabytes per year. Total data generated by humanity: estimated at 120 zettabytes by 2025.
📱 File Size Reference
SMS message: ~0.1–0.2 KB. Email (text): ~20 KB. Web page: 1–5 MB average. MP3 song (128 kbps, 4 min): ~4 MB. HD photo (DSLR): 5–25 MB. 4K video (1 min): 350–400 MB. DVD: 4.7 GB. Blu-ray: 25–50 GB. Operating system: 5–20 GB. Modern video game: 50–200 GB.
🌐 Network Speed vs Storage
Network speeds: bits per second (bps, Kbps, Mbps, Gbps). File sizes: bytes (KB, MB, GB). Converting: download time (seconds) = file size (bytes) ÷ speed (bytes/second) = file size (MB) ÷ (speed Mbps ÷ 8). A 1 GB file on 100 Mbps connection: 1,000 MB ÷ (100 ÷ 8) = 1,000 ÷ 12.5 = 80 seconds. ISPs advertise in Mbps; you experience downloads in MB/s.
☁️ Cloud Storage Context
Free tiers: Google Drive 15 GB, iCloud 5 GB, Dropbox 2 GB, OneDrive 5 GB. Paid: typically $2–10/month per 100 GB–2 TB. Mobile data plans: 5–100 GB/month (cellular). The average smartphone user generates 3–5 GB of photos/year. A 4K movie is 15–25 GB. Understanding sizes helps evaluate whether storage plans meet actual needs.
Data Size in Technology
Understanding internet speeds
'100 Mbps broadband' means 100 megabits per second — not megabytes. Divide by 8 to get megabytes per second: 100 Mbps = 12.5 MB/s. Practical download speeds: a 1 GB game update at 100 Mbps takes approximately 80 seconds (assuming no overhead). Gigabit internet (1 Gbps) provides 125 MB/s — downloading that 1 GB game in 8 seconds. Upload speeds are typically 10–30% of download speeds on asymmetric connections like cable or DSL; fibre broadband often offers symmetrical speeds.
Storage planning for photography and video
Professional photographers and videographers need to plan storage carefully. RAW photos: 20–45 MB each depending on camera. A 1-day professional shoot: 500–2,000 photos = 10–90 GB. 4K video: 4–8 GB per hour (H.264), 20–50 GB per hour (ProRes). A wedding videographer shooting 8 hours at 4K: 30–400 GB of footage. Best practice: 3-2-1 backup rule — 3 copies of data, on 2 different media types, with 1 offsite. For 100 GB of photos: local drive + external drive + cloud = 3 copies total.
Data centre and enterprise scale
Modern data centres operate at petabyte and exabyte scale. Facebook stores approximately 250 billion photos (approximately 100 petabytes). YouTube receives 500 hours of video per minute. The entire printed collection of the US Library of Congress is approximately 10 TB. All human speech ever spoken is estimated at approximately 5 exabytes. Understanding the scale from bytes to zettabytes contextualises both individual file management decisions and the infrastructure requirements of large-scale digital services.
A "1 TB" hard drive (decimal, as sold) contains exactly 1,000,000,000,000 bytes. Converted to binary units: 1,000,000,000,000 ÷ 1,073,741,824 = 931.32 GiB — which is exactly the figure Windows/macOS shows for a "1 TB" drive, since the OS reports in binary (GiB) but often still labels it "GB."
Avoid These Mistakes
Assuming "GB" always means the same thing
A drive manufacturer's GB (decimal, 1,000-based) and your operating system's displayed GB (usually actually binary, 1,024-based, and more accurately called GiB) are different units wearing the same label — this is the single most common data-size confusion.
Confusing bits and bytes in network speeds
"100 Mbps" is 100 megabits per second, not megabytes — divide by 8 to get the actual download speed in MB/s (100 Mbps ≈ 12.5 MB/s).
Assuming a drive's "missing" space is a defect
A "1 TB" drive showing ~931 GB in your file manager isn't missing capacity — it's decimal-to-binary unit conversion, not lost storage (a small amount is separately used for the file system itself, which is a different, much smaller effect).
Frequently Asked Questions
How many MB in a GB?
1 GB = 1,024 MB (binary, used by operating systems) or 1,000 MB (decimal, used by storage manufacturers). This discrepancy is why a '1TB' hard drive shows as ~931 GB in Windows.
What is the difference between Megabits and Megabytes?
1 Byte = 8 bits. Internet speeds are measured in Megabits per second (Mbps), while file sizes use Megabytes (MB). So a 100 Mbps connection transfers 12.5 MB per second. This is why download speeds appear lower than your advertised connection speed.
How large is a 4K movie?
A typical 4K movie is 50–100 GB in high-quality Blu-ray format, or 15–25 GB in compressed streaming format (Netflix/Disney+). A 1080p HD movie is roughly 4–10 GB. A standard DVD (480p) holds about 4.7 GB.
What is a Petabyte?
1 Petabyte (decimal) = 1,000 Terabytes = 1,000,000 Gigabytes. (The binary equivalent, 1 Pebibyte, = 1,024 Tebibytes = 1,048,576 Gibibytes.) To put it in perspective: 1 PB could store approximately 250,000 HD movies or 20 million 4-drawer filing cabinets full of text.
References
🏛️ IEC 80000-13
The International Electrotechnical Commission standard that formally defines the binary prefixes (KiB, MiB, GiB, TiB) to distinguish them from the decimal SI prefixes (KB, MB, GB, TB) used here.
📄 Storage manufacturer specifications
Drive and storage manufacturers publish decimal capacity on packaging and spec sheets — confirm against your specific product's data sheet if the displayed capacity doesn't match expectations.