How to use the video and audio file size calculator
- Choose what to find: file size from bitrate, the bitrate that fits a file size, or the size of uncompressed audio.
- Enter the length in hours, minutes and seconds.
- For file size, enter the video bitrate in megabits per second and the audio bitrate in kilobits per second. For a size limit, enter the limit and the audio bitrate. For uncompressed audio, enter the sample rate, bit depth and channels.
- Read the result in decimal units (MB, GB) and binary units (MiB, GiB).
Formula
Bytes = (video bits per second + audio bits per second) x seconds / 8
Bitrate from size = bytes x 8 / seconds
Uncompressed audio bitrate = sample rate x bit depth x channels
1 MB = 1,000,000 bytes, 1 GB = 1,000,000,000 bytes, 1 MiB = 1,048,576 bytes, 1 GiB = 1,073,741,824 bytes
The results are for the media data at an average bitrate, without container overhead.
A 90 minute video
At 8 Mbps of video and 128 kbps of audio the total is 8,128 kbps. Over 5,400 seconds that is 5,486,400,000 bytes, which is 5.49 GB or 5.11 GiB, or 60.96 MB per minute.
To fit a 4 GB limit in 90 minutes with 128 kbps audio, the total bitrate is 5,925.9 kbps, so the video can use 5,797.9 kbps (5.798 Mbps). For a 700 MB limit it is 909.0 kbps. Uncompressed CD style audio (44,100 Hz, 16 bits, 2 channels) is 1,411.2 kbps, which is 10.58 MB a minute and 635.04 MB an hour.
Bits, bytes and the two kinds of units
Bitrates are in bits per second, and file sizes are in bytes, which are 8 bits each. Decimal units use powers of 1,000 and are what storage makers and most websites use. Binary units use powers of 1,024 and are what some operating systems show, with the names MiB and GiB. The tool shows both so that the number matches the one you see elsewhere.
Streaming and upload sites may re-encode your file, so the final size can differ from what you calculate for the original.
Why the result is an estimate
A variable bitrate file moves around its average, so a file can be larger or smaller than the figure. The container, such as MP4 or MKV, adds a little overhead for headers and indexes. If you are aiming at a hard limit, aim a few percent below it.
For a size limit, remember that the audio takes its share first, and the video gets what is left. For other conversions, see the unit converter, the time duration calculator and the decimal hours calculator. The number base converter helps with binary values.
Assumptions and limits
- Sizes use the average bitrate you enter and do not include container overhead.
- Decimal and binary units are both shown and are defined in the formula section.
- Uncompressed audio is raw PCM. A WAV or AIFF file adds a small header.
- Compressed audio and video can be much smaller or larger depending on the encoder.
Frequently asked questions
How do I calculate video file size?
Add the video and audio bitrates, multiply by the length in seconds and divide by 8 to get bytes. At 8,128 kbps for 5,400 seconds that is about 5.49 GB.
What is the difference between GB and GiB?
A GB is 1,000,000,000 bytes and a GiB is 1,073,741,824 bytes, so a GiB is about 7.4% larger. Some systems show GiB and call it GB.
How do I find the bitrate for a size limit?
Multiply the limit in bytes by 8 and divide by the seconds to get the total bitrate, then subtract the audio bitrate to find what is left for video.
Why is my real file a different size?
Variable bitrate encoding, container overhead and re-encoding by a site can all change the size from the estimate.