What this Video Compression Size Calculator does
The Video Compression Size Calculator estimates how much storage a video will use after compression. It uses the target video bitrate, the video's duration, and the audio bitrate to estimate a file size in decimal megabytes. The title, description, inputs, and formula describe a bitrate-based estimate, so the result is most useful when you have a planned export bitrate or an encoder's average bitrate target.
The calculation converts the two bitrates to bits per second, multiplies their combined rate by the duration in seconds, then converts bits to megabytes. It assumes that both streams maintain their stated average bitrate throughout the video. Real files can be somewhat larger or smaller because of variable bitrate encoding, container overhead, subtitles, metadata, and other streams. Treat the result as a planning estimate rather than a guaranteed file size.
A video compression calculator is useful when preparing media for a website, a client handoff, an archive, a project drive, or a content delivery workflow. It can help compare export settings before spending time rendering several versions. It does not inspect a source file, choose an encoder, or determine the visual quality a particular bitrate will produce.
How to use the Video Compression Size Calculator
Enter the settings for the version you plan to create. Use the bitrate units shown beside each input, since confusing megabits with megabytes can lead to a substantially incorrect estimate.
- Target video bitrate: Enter the average video stream bitrate in megabits per second (Mbps).
- Video duration: Enter the full runtime in minutes. For a short clip, you can enter a decimal value, such as 1.5 minutes for 90 seconds.
- Audio bitrate: Enter the audio stream bitrate in kilobits per second (kbps). Use zero if the export has no audio track.
The result is labeled Estimated File Size (MB). It uses decimal megabytes, where 1 MB equals 1,000,000 bytes. If you need an approximate value in gigabytes, divide the result by 1,000 under the same decimal convention. Operating systems and storage tools may display units differently, so a displayed figure can vary even when the underlying byte count is the same.
For example, consider a 10-minute video with an average video bitrate of 8 Mbps and audio at 192 kbps. Convert the rates to bits per second: 8 Mbps is 8,000,000 bits per second and 192 kbps is 192,000 bits per second. The combined rate is 8,192,000 bits per second. The duration is 10 × 60, or 600 seconds. The formula gives (8,192,000 × 600) ÷ 8,000,000 = 614.40 MB. This is a stream-size estimate before file container overhead.
How the Video Compression Size Calculator formula works
The formula is ((video_bitrate × 1,000,000 + audio_bitrate × 1,000) × duration_minutes × 60) ÷ 8,000,000. The first conversion changes video bitrate from Mbps to bits per second. The second changes audio bitrate from kbps to bits per second. Adding them produces an estimated combined audio and video rate.
Multiplying that combined rate by the duration in seconds gives the total number of bits. Dividing by eight converts bits to bytes. The remaining division by 1,000,000 converts bytes to decimal megabytes. The inputs allow a minimum positive bitrate and duration, preventing a zero duration from making the estimate meaningless. Audio can be set to zero when there is no audio stream.
This method is appropriate for estimating data volume from average bitrate. It does not calculate compression ratio from the original file size because no source size is requested. Nor does it predict quality from resolution, frame rate, codec, scene motion, or encoder settings. Those factors affect the bitrate you may choose, while the formula estimates the size once a bitrate is supplied.
Use cases for the Video Compression Size Calculator
Editors and producers can use the estimate to compare delivery versions. A lower target bitrate generally means fewer bits assigned to each second of video and therefore a smaller estimated file, while a higher bitrate produces a larger estimate. The calculator shows the storage consequence of the selected rates; it cannot say whether the resulting picture will be acceptable for a particular project.
It can also support practical planning across common production tasks:
- Estimate whether a batch of short social clips will fit within available working storage.
- Compare candidate export bitrates for a review copy or client preview.
- Estimate the approximate size of a long-form recording before transferring or archiving it.
- Check how much an audio track contributes to the total when preparing a spoken-word video.
- Plan upload time or transfer capacity alongside a separate estimate of network speed.
For multiple videos with the same settings, calculate one file and multiply its estimate by the number of files. That simple extension assumes every video has the same duration and average rates. If the clips differ, calculate each one separately and add the results for a closer total.
Other factors to consider when calculating video size
Many encoders use variable bitrate, adjusting the data rate as visual complexity changes. A scene with motion, texture, grain, or rapid cuts may require more data than a static scene. The average bitrate remains useful for estimating overall size, but short sections can rise above or fall below that average. If the target is a strict maximum file size, leave room for variation and verify the encoded output.
The formula includes only the video and audio streams. A finished container can add a small amount of overhead, and subtitles, alternate audio languages, chapter markers, or attachments can add more. The exact contribution depends on the export and container. For a delivery with strict size limits, encode a representative sample or a complete draft, inspect its actual size, then adjust settings if needed.
Codec and encoding choices influence how efficiently bits represent the image. Resolution, frame rate, color depth, noise, and motion also affect the bitrate needed for a desired viewing experience. These are reasons to choose a bitrate thoughtfully, but they do not change the calculator's arithmetic once the average bitrate is known. Quality should be checked on the actual content and playback conditions.
Frequently asked questions
Is the result the exact exported file size?
No. It estimates audio and video stream data from average bitrates and duration. Container overhead, metadata, subtitles, extra tracks, and bitrate variation can change the final size. Use an actual export to confirm a strict delivery limit.
Why does the calculator ask for Mbps and kbps?
Video bitrate is commonly stated in megabits per second, while audio bitrate is often stated in kilobits per second. The formula converts both to bits per second before adding them, which keeps their units consistent.
Can I use this for a video with no audio?
Yes. Enter zero for audio bitrate. The estimate then uses only the target video bitrate and duration.
Does a smaller estimated size mean the video will look worse?
Not necessarily in every case, but reducing bitrate gives the encoder fewer bits to represent the material. The visual result depends on the content, codec, resolution, frame rate, and encoder settings. Compare test exports at the intended playback size before choosing a final setting.
What does MB mean in the result?
The result uses decimal megabytes, with 1 MB equal to 1,000,000 bytes. Some devices and software use binary units or label them differently, so their displayed size may not match the calculator's MB figure exactly.