Work backwards from an upload or delivery limit to an average video bitrate. Or estimate the size of a video using a bitrate you already chose. Include all audio tracks in the combined audio value.
Read the number as a budget
A 10-minute file with a 50 MB limit, 128 kbps audio and a 5% reserve leaves about 0.505333 Mbps for video. That result says how little space is available. It does not promise that detailed 1080p footage will look good at that bitrate. Shortening the video or increasing the delivery limit may be the more useful decision.
If you already chose 8 Mbps video and 384 kbps audio, 10 minutes contains 628.8 MB of payload before extra streams and overhead. A 5% reserve as defined here makes the planning total about 661.895 MB: the payload occupies 95% of that total. This differs from simply adding 5% to the payload.
The formulas and units
Payload bytes = (video bps + combined audio bps) × seconds ÷ 8. For a fixed limit, reserve the chosen share of the total first, divide the remaining bytes by duration, then subtract audio. The calculator shows the calculation used beside the result.
Bitrates use decimal units: 1 Mbps is 1,000,000 bits per second and 1 kbps is 1,000. File size can use either family. NIST’s binary-prefix definitions distinguish 1 MB = 1,000,000 bytes from 1 MiB = 1,048,576 bytes, and 1 GB = 1,000,000,000 bytes from 1 GiB = 1,073,741,824 bytes. Match the unit in the actual delivery requirement.
Use the result in your export workflow
Enter an average bitrate only where your editor exposes a suitable numerical control. A quality label such as Recommended is not an exact Mbps value. Variable bitrate, additional tracks, metadata and the encoder’s rate control can change the finished size. Keep headroom under a strict limit and inspect the actual exported file.
For a platform-oriented starting profile, use the CapCut export settings recommender. For the controls and delivery decisions, follow the export settings guide. If the file is already too large, the compression guide explains the tradeoffs beyond changing one number.
Why are resolution, frame rate and codec not inputs?
Once the average bitrate is fixed, the payload calculation uses that bitrate and duration. Resolution, motion, codec and encoder settings affect the quality you can achieve within the budget. This calculator does not turn them into an unsupported quality score.
Are the values sent anywhere?
The calculation uses the numbers in this form locally. It does not inspect or upload a video and does not store the entries. The website can still load its normal analytics and theme services.