Video Bitrate & File Size Calculator
Convert between video bitrate, duration and file size. Find the bitrate that hits a target file size, or estimate how big an export will be.
The formula behind it
Bitrate is the amount of data a video uses every second. Because bitrate is measured in bits and file sizes in bytes, the conversion has one extra step: divide by eight. The whole calculation is size (MB) = (video Mbps + audio Mbps) × seconds ÷ 8. Going the other way, bitrate = size × 8 ÷ seconds.
This tool uses decimal megabytes (1 MB = 1,000,000 bytes), which is how most upload limits and encoders count. Windows File Explorer shows binary units, so a file this calculator calls 1,000 MB will appear as about 954 MB there.
When to use each mode
Use estimate file size when you already know your export settings and want to check that the result will fit on a drive, an upload form or an email limit. Use find bitrate when a platform gives you a hard cap, such as a 25 MB chat attachment or a 2 GB course-platform limit, and you need the highest bitrate that still fits. Enter that number into HandBrake, Premiere Pro, DaVinci Resolve or FFmpeg and use two-pass encoding for the most accurate result.
Picking a sensible bitrate
Hitting a size is only half the job. If the bitrate you get back is very low for the resolution, the picture will fall apart into blocks. As a rough guide for H.264: 1080p at 30 fps looks good from about 5 Mbps, 720p from about 2.5 Mbps and 480p from about 1 Mbps. HEVC and AV1 manage similar quality at 30 to 50 percent less. If your target bitrate is below those numbers, drop the resolution rather than starving a big frame of data. Our guide to video bitrate explains the trade-offs in detail, and the compression guide walks through export settings.
Frequently asked questions
How do I calculate video file size from bitrate?
File size in megabytes equals total bitrate in megabits per second, times duration in seconds, divided by 8. A 10-minute video at 8 Mbps video plus 128 kbps audio is about 610 MB.
What bitrate should I use to hit a target file size?
Divide the target size in megabits by the duration in seconds, then subtract the audio bitrate. For a 100 MB, 5-minute clip that gives about 2.67 Mbps total, or roughly 2.54 Mbps for video with 128 kbps audio.
Is the result exact?
It is very close for constant bitrate. With variable bitrate or two-pass encoding the average lands near the target, but containers add a small overhead, usually under 1 to 2 percent.