About the Video File Size Calculator
The size of a video file depends on two things: how many bits it uses for each second of video and sound, the bitrate, and how long it lasts. This calculator multiplies them for you. Enter the video bitrate in megabits per second, the audio bitrate in kilobits per second and the duration, and it gives the file size in megabytes and gigabytes. It can also work backwards from a target file size to the bitrate you can afford. Type the video bitrate, the audio bitrate and the duration, or a target size and the duration and the video file size appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Video File Size Calculator
- 1Enter the video bitrate, the audio bitrate and the duration, or a target size and the duration.
- 2Pick the units or options from the menus if the video file size tool offers them.
- 3Read the video file size in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the video file size
Video makers use the figure to plan storage and uploads, streamers to match their upload speed and viewers to guess how much data a stream will use. Editors use the reverse calculation to export a video to fit an email or a disc.
Typical video bitrates: about 5 Mbps for 1080p streaming, 8 to 12 Mbps for good quality 1080p files and 25 Mbps or more for 4K. Audio is usually 96 to 320 kbps. Variable bitrate files use less on simple scenes, so the actual size is an average.
How the video file size is worked out
File size = (video bitrate + audio bitrate) × duration ÷ 8. Bitrate for a size = size × 8 ÷ duration. Decimal units: 1 GB is 1,000,000,000 bytes. One hour of video at 8 Mbps with 128 kbps audio is 3.66 GB (3,657.6 MB, about 3.41 GiB), or 61 MB per minute. To fit a one hour video into 4 GB, the average bitrate of video and audio together can be 8.89 Mbps.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- File size from bitrate
- Bitrate from file size
- MB, GB and GiB
Mistakes to avoid with video file size
The result is an estimate: containers add a small overhead, and variable bitrates can vary. Operating systems often show sizes in binary units, so a decimal 4 GB file shows as 3.73 GiB. Leave a little space when you aim at a limit.
On phone and computer
On a phone, type into the boxes one after another and read the video file size underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the video file size move. The video file size calculator works the same on both. File size comes from bitrate and length, and these tools give more context. Plan a connection with the Bandwidth Calculator, convert sizes with the Data Storage Converter, and check the picture shape with the Aspect Ratio Calculator.
Features
- Bitrate times length
- Capital B is a byte
- VBR gives an average
- Clear messages when the video file size inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate video file size?
File size = (video bitrate + audio bitrate) × duration ÷ 8. Bitrate for a size = size × 8 ÷ duration. Decimal units: 1 GB is 1,000,000,000 bytes. One hour of video at 8 Mbps with 128 kbps audio is 3.66 GB (3,657.6 MB, about 3.41 GiB), or 61 MB per minute. To fit a one hour video into 4 GB, the average bitrate of video and audio together can be 8.89 Mbps.
What is the formula for video file size?
File size = (video bitrate + audio bitrate) × duration ÷ 8. Bitrate for a size = size × 8 ÷ duration. Decimal units: 1 GB is 1,000,000,000 bytes. The video file size calculator applies it exactly and rounds only the displayed answer to six significant figures.
How many GB is one hour of video?
At 8 Mbps about 3.6 GB. At 5 Mbps about 2.3 GB, and at 25 Mbps about 11.3 GB.
What is the difference between MB and Mb?
A capital B is a byte and a small b is a bit. A byte is eight bits.
Why does my file show a different size?
Computers may use binary units (GiB), where 1 GiB is 1.074 GB.
Is this video file size calculator free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.