How Video File Size Works
Digital video is a sequence of still images displayed rapidly to create motion. Each image—called a frame—contains pixel data that occupies a measurable amount of disk space. The total file size is determined by multiplying three core parameters: the data size of each frame, the number of frames per second (frame rate), and the total duration in seconds.
For example, a 1080p uncompressed 8-bit RGB frame at 1920 × 1080 resolution occupies roughly 6.2 MB. At 24 fps over 60 seconds, that single minute expands to nearly 9 GB. Compression codecs (like H.264, ProRes, or REDCODE) drastically reduce this footprint by removing redundant or imperceptible data.
- Uncompressed or visually lossless formats preserve maximum quality but demand extreme storage: professional workflows often require terabytes for short projects.
- Streaming codecs (H.264, VP9, AV1) optimise for internet delivery, achieving 1.6–1.8 GB per two-hour feature at 720p.
- Intermediate formats (ProRes, DNxHD) balance editability and file size, commonly used in post-production.
Video File Size Calculation
The fundamental relationship between frame size, frame rate, and duration is:
File Size = Frame Size × Frame Rate × Time
Where Frame Size (in bytes or megabytes) is determined by:
Frame Size = Horizontal Resolution × Vertical Resolution × Color Depth ÷ 8
For a practical example: a 1080p video at 24 fps for 60 seconds with 24-bit colour (3 bytes per pixel):
Frame Size = 1920 × 1080 × 24 ÷ 8 = 6.2208 MB
File Size = 6.2208 MB × 24 fps × 60 sec = 8,957.952 MB ≈ 8.96 GB
Frame Size— Total data in one video frame, measured in bytes or megabytes. Depends on resolution and colour bit depth.Frame Rate— Number of individual frames displayed per second, typically 24, 30, or 60 fps.Time— Duration of video in seconds. Multiply minutes by 60 to convert.Horizontal Resolution— Width of the video in pixels (e.g., 1920 for 1080p).Vertical Resolution— Height of the video in pixels (e.g., 1080 for 1080p).Colour Depth— Bits per pixel (e.g., 8-bit = 1 byte, 24-bit = 3 bytes per pixel for RGB).
Binary vs. Decimal: MB, MiB, and Storage Math
File sizes reported by operating systems and manufacturers sometimes differ due to competing unit definitions. A megabyte (MB) in marketing traditionally means 1,000,000 bytes (decimal), while a mebibyte (MiB) means 1,048,576 bytes (binary, or 2²⁰). Hard drive manufacturers favour decimal units to report larger capacity figures; operating systems often use binary.
This 4.9% discrepancy compounds across large files. A drive advertised as 1 TB (1,000,000,000,000 bytes) holds approximately 931 GiB in binary terms. When planning storage for video projects, account for this difference and expect to lose 5–10% of advertised capacity to file system overhead.
- Use MB (megabyte) for industry standard figures and marketing specs.
- Use MiB (mebibyte) when checking actual disk space available on your computer.
- Always assume actual usable space is slightly less than advertised due to formatting and file system metadata.
Real-World File Sizes by Format and Codec
Codec choice has the largest impact on file size. Here are approximate storage footprints for common scenarios:
- 1 minute of 1080p uncompressed 8-bit RGB: ~8.96 GB. This is standard in professional post-production when editing demands maximum quality.
- 1 minute of 4K RAW (REDCODE28): ~1.76 GB at 24 fps. Used in cinema workflows; still enormous despite compression.
- 1 minute of 4K ProRes (iPhone 13): ~5.5 GB. A practical middle ground for high-end mobile capture.
- 2 hours of 720p ProRes 422: ~55.26 GB. Typical for professional-grade editing intermediate.
- 2 hours of 720p streaming (H.264): ~1.6–1.8 GB. Standard for downloaded content or video-on-demand libraries.
Choose your codec based on workflow requirements: prioritise compression for archival and delivery, lossless or intermediate codecs for active editing.
Practical Considerations for Video Storage
Several real-world factors can skew your file size estimates and affect project planning.
- Compression Ratio Varies by Content — Complex, high-motion footage (sports, action scenes) compresses less efficiently than static or low-motion content (interviews, slide presentations). The same codec applied to different material produces vastly different file sizes. Always test encode a sample before committing to a full project.
- Frame Rate and Duration Multiply Quickly — A 50% increase in duration doubles file size proportionally. Doubling frame rate (24 to 48 fps) doubles storage without improving perceived smoothness for most viewers. Match frame rate to your output platform: 24 fps for cinema, 30 fps for NTSC video, 25 fps for PAL, 60 fps only if slow-motion is essential.
- Metadata, Audio, and Container Overhead — This calculator estimates video data alone. Audio tracks, subtitles, and container metadata (MP4, MKV, MOV) add 5–15% extra. Professional formats with rich metadata and colour grading data can add significantly more.
- Lossless vs. Lossy Compression Trade-Offs — Lossless codecs (ProRes, DNxHD) are safer for editing but much larger. Lossy codecs (H.264, HEVC) shrink files dramatically but degrade quality with each re-encode. Plan your workflow: capture or transcode to lossless intermediates once, then derive final delivery versions as needed.