MundoKit

Video file size calculator

Enter duration and average video and audio bitrates to estimate file size. Set a target size to find the available video bitrate after audio and overhead.

Inputs
minutes
kbps
Illustrative input, not a quality recommendation.
kbps
%
Enter your own allowance; no universal overhead rate is assumed.
Uses the selected size unit. Ignored when a platform preset is selected.

Results

Estimated file size
614.4 MB
Video bitrate to fit target
1,141.333 kbps
Total bitrate budget
1,333.333 kbps
Target size
100 MB
Estimated size fits target
No
  • Uses average bitrates. Variable bitrate encoders and container metadata can change actual size. Leave a safety margin below an upload cap.

Results update as you type. The share link stores your inputs after the # in the address, which is not sent to our server, but anyone you send it to can read them.

How it works

Bitrate measures bits per second, as used by FFmpeg. NIST defines a byte as 8 bits and a kilobit as 1,000 bits. Add average video and audio kbps, multiply by seconds, then divide by 8 to get bytes. Our overhead input adds a user-selected percentage of encoded payload; it is not a measured container rate.

size bytes = seconds × (video kbps + audio kbps) × 1,000 ÷ 8 × (1 + overhead % ÷ 100) video kbps budget = target bytes × 8 ÷ seconds ÷ 1,000 ÷ (1 + overhead % ÷ 100) − audio kbps

MB means 1,000,000 bytes; MiB means 1,048,576 bytes. The toggle changes custom target interpretation and displayed sizes. Platform presets retain their fixed byte budgets. Calculations keep full precision; displayed sizes and bitrates round to at most three decimal places. Leave a margin below a cap rather than rounding the bitrate upward.

Upload presets were checked on November 14, 2026: YouTube allows up to 256 GB or 12 hours, whichever is less. Account verification is required for videos longer than 15 minutes. Discord's developer reference states a default 20 MiB per file, with higher limits possible by account or server. Its consumer FAQ labels this 20MB and notes experiments. Use your account's actual allowance as a custom target if it differs. Presets do not check all upload eligibility rules.

Worked examples

Ten minutes at 8,000 + 192 kbps

600 × 8,192 × 1,000 ÷ 8 = 614,400,000 bytes with zero overhead: 614.4 MB or 585.9375 MiB (displayed as 585.938 MiB).

Fit five minutes into 100 MB

With zero overhead, the total budget is 100,000,000 × 8 ÷ 300 ÷ 1,000 = 2,666.666… kbps. After 128 kbps audio, the video budget is 2,538.667 kbps when rounded for display.

Add a chosen overhead allowance

For one minute at 1,000 kbps video and no audio, payload is 7.5 MB. A user-chosen 2% overhead makes the estimate 7.65 MB.

Frequently asked questions

Does resolution determine file size?
Duration and average encoded bitrate determine the payload size. Resolution and codec affect the bitrate needed for a given quality, but are not enough to calculate file size alone.
What is the difference between MB and MiB?
1 MB is 1,000,000 bytes. 1 MiB is 1,048,576 bytes. The same file has a smaller numerical size when expressed in MiB.
What overhead percentage should I enter?
There is no universal percentage. It depends on the container, streams and metadata. Enter an allowance based on your workflow; the default zero excludes overhead.
Why does my exported file differ?
Variable bitrate settings may target quality rather than an exact average bitrate. Metadata, extra audio tracks and container overhead also change size. Use the sum of all audio bitrates.
Can the target be too small for audio?
Yes. If the audio bitrate alone exceeds the total bitrate budget, the tool reports that no video bitrate can fit. Reduce audio bitrate, duration or overhead, or raise the target size.

Sources

Last reviewed 2026-11-14; next review due by 2027-02-12. The method is written out above so you can check our math.