About the Video File Size Calculator
This video file size calculator turns bitrate and running time into a file size, and works backwards to tell you the bitrate you need to fit a video into a given size. Enter the video bitrate in megabits per second, the audio bitrate in kilobits per second and the duration, and it returns the size in megabytes and gigabytes, plus how much space each minute and each hour of footage uses.
It is useful for videographers sizing memory cards and hard drives for a shoot, editors choosing export settings that fit an upload limit, streamers estimating storage for recordings, and anyone squeezing a video under an email or messaging attachment cap. The table shows how the file grows for common durations at the same bitrate.
Sizes use decimal units (1 MB = 1,000,000 bytes, 1 GB = 1,000 MB), which is how cameras, cards and drives are labelled; the binary GiB that some operating systems display is shown too. Results assume a constant total bitrate and ignore the small container overhead (typically around 1%), so variable-bitrate encodes can come out a little larger or smaller.
How to use the video file size calculator
- 1Choose whether you want the file size or the bitrate for a target size.
- 2Enter the video bitrate from your camera or encoder settings, or the target size.
- 3Enter the audio bitrate (0 for no audio).
- 4Enter the duration in hours, minutes and seconds.
- 5Read the file size or bitrate, and use the table to plan storage for longer recordings.
Formula and method
Bitrate is the amount of data recorded per second, measured in bits. Adding the video and audio bitrates gives the total stream rate; multiplying by the duration in seconds gives megabits, and dividing by 8 converts bits to bytes, giving megabytes. For example, 50 Mbps for 600 seconds is 30,000 megabits, or 3,750 MB.
To hit a target size the equation is reversed: the target in megabytes × 8 ÷ seconds gives the total bitrate, and subtracting the audio bitrate leaves the video bitrate to set in your encoder. Decimal units are used throughout (1 Mbps = 1,000,000 bits per second, 1 GB = 10⁹ bytes); the GiB figure divides the byte count by 2³⁰.
- Mbps
- Megabits per second (10⁶ bits/s)
- kbps
- Kilobits per second (10³ bits/s)
- ÷ 8
- Converts bits to bytes
Worked examples
10 minutes of 4K at 50 Mbps with 320 kbps audio
The total bitrate is 50 + 0.32 = 50.32 Mbps. Over 600 seconds that is 30,192 megabits ÷ 8 = 3,774 MB, or about 3.77 GB (3.51 GiB in binary units).
Fit a 45-minute talk into 2 GB
2 GB is 2,000 MB or 16,000 megabits. Spread over 2,700 seconds that allows 5.93 Mbps in total; subtracting 0.128 Mbps of audio leaves about 5.80 Mbps for the video stream.
Two hours of 1080p at 8 Mbps
8.192 Mbps × 7,200 s ÷ 8 = 7,372.8 MB, about 7.37 GB in total, or roughly 3.69 GB per hour of footage.
Frequently asked questions
How do I calculate video file size?+
Multiply the total bitrate in megabits per second by the duration in seconds, then divide by 8 to get megabytes. For example, 20 Mbps for 5 minutes is 20 × 300 ÷ 8 = 750 MB.
How many GB is an hour of 4K video?+
It depends on the bitrate. At 50 Mbps an hour is about 22.5 GB, at 100 Mbps about 45 GB, and high-end codecs such as ProRes 422 HQ at 4K can exceed 300 GB per hour.
Why is my exported file a different size than calculated?+
Most encoders use variable bitrate, so the average can differ from the target, and containers such as MP4 add a little overhead. Two-pass encoding hits a target size most accurately.
What is the difference between Mbps and MBps?+
Mbps is megabits per second and MBps (or MB/s) is megabytes per second. There are 8 bits in a byte, so 100 Mbps equals 12.5 MB/s.
Why does my computer show a smaller size in GB?+
Some operating systems, including Windows, count gigabytes in binary units (1 GiB = 1,073,741,824 bytes), which are about 7% larger than decimal gigabytes. The calculator shows both.