Video File Size Calculator
Estimate a video file's size from its resolution, bitrate and duration.
What is the Video File Size Calculator?
This tool estimates a video's output file size from its bitrate and duration, or works backward to find the bitrate needed to hit a specific target file size — useful when exporting for a platform with an upload size limit.
The formula
File Size (MB) = (Video Bitrate + Audio Bitrate) × Duration (seconds) ÷ 8 ÷ 1024, converting combined bitrate (in bits per second) and duration into megabytes. To solve for required bitrate instead, the same formula is rearranged to solve for bitrate given a target size.
How to use it
- Choose whether you're estimating file size from a known bitrate, or solving for the bitrate needed to hit a target size.
- Enter duration, and either your bitrate or target file size, plus audio bitrate.
This calculates the theoretical output of constant-bitrate encoding; variable bitrate (VBR) encoding, which most modern encoders use by default, produces a similar but not identical final size depending on the content's complexity.
Want the "why" behind this tool? Read Why the Same Video Length Can Produce Wildly Different File Sizes.