/video-file-size-calculator
Video File Size Calculator
Estimate a video’s file size from runtime and average bitrate. The result includes decimal megabytes and gigabytes plus binary gibibytes, making it useful for storage planning, upload estimates, and bitrate comparisons.
/media/video-file-size
Uses average bitrate. Variable-bitrate encodes can differ from the estimate.
Video file size formula
Add video bitrate and audio bitrate after converting them to the same unit. Multiply the total bits per second by runtime in seconds, then divide by eight to get bytes. For example, 8 Mbps video plus 192 kbps audio equals 8.192 Mbps. At a constant average, ninety minutes uses about 5.53 GB.
Average bitrate matters
Constant-bitrate media stays near the entered rate. Variable-bitrate encoding spends more data on complex scenes and less on simple ones, so the final size depends on the achieved average rather than a maximum setting. Two-pass encoding can target an average more closely, while quality-based encoding may produce a less predictable size.
GB is not GiB
Storage vendors use decimal units: 1 GB equals 1,000,000,000 bytes. Many operating systems and technical tools use binary units: 1 GiB equals 1,073,741,824 bytes. Both results describe the same bytes, but the GiB number is smaller.
What is not included
Container overhead, subtitles, multiple audio tracks, metadata, thumbnails, and streaming manifests add data. Usually that overhead is modest relative to the video stream, but it can matter for very short clips or many auxiliary tracks. Use the measured average bitrate from a completed encode when exact storage planning is required.
Frequently asked questions
How do you calculate video file size from bitrate?
Add the video and audio bitrates, multiply by the runtime in seconds, and divide by eight to convert bits to bytes.
Why are GB and GiB different?
A decimal gigabyte is one billion bytes. A binary gibibyte is 1,073,741,824 bytes, so the same file has a smaller numeric value in GiB.