File size and digital storage
File-size questions rarely end with a conversion. You may need to find out whether a webpage meets its size budget, how many photographs fit on a drive, how long security-camera storage will last or how much capacity a backup plan requires. UnitConversionPlus combines practical calculators for those tasks with direct kB, MB, GB and TB converters and clear explanations of decimal and binary units.
Start with the problem you need to solve. If you only need a numerical result, use the converter directory below. Unless a binary unit such as KiB, MiB, GiB or TiB is explicitly named, UnitConversionPlus's file-size converters use decimal units.
Choose a File-Size Calculator, Planner or Guide
These tools use file-size conversions as part of a wider calculation. Each one is organised around a practical question and explains its assumptions.
Website Page-Size and Download Planner
Add HTML, CSS, JavaScript, images and other resources in kB or MB. Compare the result with a page-size budget, estimate download time, project monthly visitor traffic and compare two webpages.
Useful for: website owners, developers, editors and performance reviews.
Image Compressor and Bandwidth-Savings Estimator
Compress an image in the browser, compare its original and reduced size, estimate its contribution to page weight and calculate potential bandwidth savings across repeated page views.
Useful for: product images, articles, portfolios and mobile-friendly pages.
Media Library and Storage-Capacity Planner
Combine several media categories, account for backup copies, compare the total with usable device capacity and forecast how a library may grow.
Useful for: photographs, music, documents, video and USB or SSD planning.
Video Compression and Storage Comparison
Compare two encoding settings, calculate actual bitrate and compression ratio, project a complete video's output size and estimate how many files fit within a storage limit.
Useful for: video production, delivery copies and archive planning.
File Storage Allocation Planner
Add multiple file categories in kB or MB, calculate required storage or the number of files a capacity can hold, and compare the result with common device sizes using an allocation chart.
Useful for: document collections, application assets and mixed file libraries.
Security-Camera Storage and Retention Planner
Model several camera groups, recording schedules and bitrates. Calculate storage required for a target retention period or estimate retention from available capacity, including RAID usable-space planning.
Useful for: homes, offices, shops and multi-camera installations.
Server Backup Capacity and Retention Planner
Combine multiple protected workloads, full and incremental schedules, growth assumptions, retention rules and backup-copy locations. View a month-by-month capacity forecast or estimate retention from available space.
Useful for: servers, databases, business systems and backup repositories.
Computer RAM History and Capacity Guide
Follow memory capacity from early kilobyte systems to modern gigabyte-scale computers and AI hardware, with a historical reference table and questions about size, cost and development.
Useful for: computing history, education and understanding scale.
Direct kB, MB, GB and TB Converters
Use these pages when the conversion itself is the main task. Decimal units move in steps of 1,000: moving to a larger unit divides by 1,000 for each step, while moving to a smaller unit multiplies by 1,000.
| Conversion | Decimal rule | Related practical topic |
|---|---|---|
| kB to MB | MB = kB ÷ 1,000 | Webpage resource totals and download planning |
| MB to kB | kB = MB × 1,000 | Image compression and bandwidth savings |
| MB to GB | GB = MB ÷ 1,000 | Media libraries, devices and backup copies |
| GB to MB | MB = GB × 1,000 | Video compression and output storage |
| kB to GB | GB = kB ÷ 1,000,000 | Computer RAM history and capacity |
| GB to kB | kB = GB × 1,000,000 | Mixed file collections and allocation |
| GB to TB | TB = GB ÷ 1,000 | Camera retention and RAID capacity |
| TB to GB | GB = TB × 1,000 | Server backups and retention planning |
Binary units use steps of 1,024 instead. For example, 1 GiB equals 1,024 MiB, whereas 1 GB equals 1,000 MB. Do not substitute GB for GiB when a specification explicitly names the binary unit.
Quick File-Size Reference
| Unit | Decimal size | Common context |
|---|---|---|
| bit (b) | One binary digit | Network and connection speeds |
| byte (B) | 8 bits | Foundation of file-size measurement |
| kilobyte (kB) | 1,000 bytes | Small documents, code, icons and webpage resources |
| megabyte (MB) | 1,000 kB | Photographs, audio, documents and short video |
| gigabyte (GB) | 1,000 MB | Apps, films, games, mobile data and device storage |
| terabyte (TB) | 1,000 GB | Drives, camera systems, servers and backups |
| petabyte (PB) | 1,000 TB | Data centres and large scientific datasets |
Typical file sizes vary substantially with format, quality, duration and content. A “photo” or “video” therefore has no single reliable size; use the measured file or an appropriate estimator when planning capacity.
Decimal and Binary Units Are Related but Not Interchangeable
Decimal prefixes follow powers of 1,000. Binary prefixes follow powers of 1,024. The IEC introduced the names kibibyte, mebibyte, gibibyte and tebibyte to make the distinction explicit. Older software and documentation sometimes use kB, MB or GB for binary-sized values, which is a major source of apparent disagreement.
| Decimal unit | Bytes | Binary unit | Bytes |
|---|---|---|---|
| 1 kB | 1,000 | 1 KiB | 1,024 |
| 1 MB | 1,000,000 | 1 MiB | 1,048,576 |
| 1 GB | 1,000,000,000 | 1 GiB | 1,073,741,824 |
| 1 TB | 1,000,000,000,000 | 1 TiB | 1,099,511,627,776 |
| 1 PB | 1,000,000,000,000,000 | 1 PiB | 1,125,899,906,842,624 |
Why the “1.44 MB” Disk Was a Mixed-Unit Exception
The familiar 3.5-inch disk held 1,474,560 bytes. Its “1.44 MB” label came from dividing 1,440 KiB by 1,000, effectively combining a binary-sized kilobyte with a decimal multiplier. It is a useful historical reminder to check the definition behind a label rather than relying on the unit name alone.
Why a 1 TB Drive May Appear as About 931 GiB
A drive sold as 1 TB contains 1,000,000,000,000 bytes before formatting and system use. Dividing that same number of bytes by 1,073,741,824 bytes per GiB gives approximately 931.32 GiB. No capacity vanished in that calculation; the number changed because the size of the reporting unit changed.
| Advertised capacity | Bytes | Equivalent binary capacity |
|---|---|---|
| 128 GB | 128,000,000,000 | 119.21 GiB |
| 256 GB | 256,000,000,000 | 238.42 GiB |
| 512 GB | 512,000,000,000 | 476.84 GiB |
| 1 TB | 1,000,000,000,000 | 931.32 GiB |
| 2 TB | 2,000,000,000,000 | 1,862.65 GiB |
Formatting, recovery partitions, file-system structures and pre-installed data can further reduce the capacity available for personal files. The security-camera storage planner and server backup planner therefore distinguish headline capacity from usable capacity.
Bits, Bytes and Transfer Time
Files are normally measured in bytes, while connection speeds are normally advertised in bits per second. One byte contains eight bits, so a 100 Mbps connection has a theoretical maximum of 12.5 MB per second—not 100 MB per second.
Estimated seconds = file size in MB × 8 ÷ connection speed in Mbps
| File | 10 Mbps | 100 Mbps | 500 Mbps |
|---|---|---|---|
| 5 MB image | 4 seconds | 0.4 seconds | 0.08 seconds |
| 100 MB update | 1 minute 20 seconds | 8 seconds | 1.6 seconds |
| 1 GB video | 13 minutes 20 seconds | 1 minute 20 seconds | 16 seconds |
| 50 GB game | About 11 hours 7 minutes | About 1 hour 7 minutes | About 13 minutes 20 seconds |
These are idealised figures. Protocol overhead, Wi-Fi conditions, network congestion, server limits and storage speed can make a real transfer slower.
Sources and Calculation Notes
- NIST: prefixes for binary multiples
- IEC: prefixes for binary multiples
- Computer History Museum: first commercial hard disk drive shipped
- IBM: RAMAC history
Conversion tables and transfer-time examples are UnitConversionPlus calculations based on the definitions stated on this page. Planner results may additionally depend on user inputs and documented assumptions. If you find an unclear label, broken source or unexpected result, please contact UnitConversionPlus.