Video File Size Calculator
File size from bitrate and length, or the bitrate to hit a target size.
About this tool
Choose a preset such as 1080p YouTube upload or 4K phone recording, or type your own video bitrate in Mbps and audio bitrate in kbps, then enter the duration. The calculator shows the file size, the video bitrate that would fit a target size, and how long you could record onto a given amount of storage.
How video file size is calculated
For any video, file size is the bitrate multiplied by the duration. Bitrates are given in megabits per second, and there are 8 bits in a byte, so size in megabytes = (video Mbps + audio Mbps) ร seconds รท 8. Ten minutes at 8 Mbps video plus 128 kbps audio is (8.128 ร 600) รท 8 โ 609.6 MB. Working backwards helps you meet upload limits: to fit a 3-minute clip into 25 MB, you can spend about 1 Mbps on video once the audio is allowed for, which is fine for a small talking-head clip but too little for 1080p action. Resolution and frame rate drive the bitrate you need: YouTube recommends about 8 Mbps for 1080p at 30 frames per second and 35โ45 Mbps for 4K, and modern phones record 1080p at around 17 Mbps and 4K HEVC at around 50 Mbps. The storage calculation tells you, for example, how many hours of footage fit on a 128 GB card. Newer codecs such as HEVC and AV1 give similar quality at lower bitrates than H.264. Honest limits: most encoders use variable bitrate, so real files vary by 10โ20%; container overhead adds a little; and drives use decimal gigabytes (1 GB = 1,000 MB), so your computer may report a smaller capacity. The video compressor, the audio bitrate calculator and the download time calculator are related.
Frequently asked questions
How big is a 10-minute 1080p video?
At 8 Mbps it's about 600 MB; phone recordings at 17 Mbps are about 1.3 GB.
How do I calculate bitrate for a target file size?
Bitrate (Mbps) = size (MB) ร 8 รท seconds, minus the audio bitrate.
How many hours of 4K video fit on 128 GB?
At about 50 Mbps, roughly 5.6 hours.
Is my data saved?
No. The calculation runs in your browser and nothing is stored or sent.