A video file’s size is set almost entirely by its bitrate — how many bits per second the encoder spends — multiplied by its length. Resolution and codec affect what bitrate you need for good quality, but once the bitrate is chosen, the size follows directly. This calculator works both ways: from bitrate to file size, and from a size limit (an upload cap, a memory card, a disc) back to the bitrate to set in your encoder.
How to use the video file size calculator
- Choose File size from bitrate or Bitrate for a target size.
- Enter the duration in hours, minutes and seconds.
- Enter the video bitrate (or the target file size), the audio bitrate for all tracks combined and the container overhead — 1% is typical for MP4 and MKV.
- Optionally choose the resolution and frame rate to get bits per pixel, the uncompressed data rate and the compression ratio.
- The table shows the same duration at typical bitrates from 480p to 4K at 60 fps.
Video size formulas
Bitrates use decimal units (1 Mbps = 1,000,000 bits/s) and sizes are reported in decimal GB with binary GiB alongside, because Windows and some apps display GiB.
Worked example: size from bitrate
A 45-minute 1080p, 30 fps recording at 8 Mbps video and 192 kbps AAC audio, in MP4 (1% overhead):
Duration: 45 × 60 = 2,700 s. Total bitrate: 8 + 0.192 = 8.192 Mbps.
Bytes: 8,192,000 × 2,700 ÷ 8 = 2,764,800,000. Plus 1%: 2.79 GB (2.60 GiB).
Quality check: 8,000,000 ÷ (1920 × 1080 × 30) = 0.129 bits per pixel — comfortable for H.264.
Uncompressed 8-bit 4:2:0 video at this size is 1920 × 1080 × 12 bits × 30 = 746.5 Mbps, so the encoder is compressing about 93 to 1.
Worked example: bitrate for a size limit
You need a 2-hour film to fit in 4 GB with 192 kbps audio. Usable bits: 4 × 10⁹ × 8 ÷ 1.01 = 31.68 × 10⁹. Per second: ÷ 7,200 = 4.40 Mbps total. Video: 4.40 − 0.19 = 4.21 Mbps. Use two-pass or constrained variable bitrate encoding and leave a little headroom so peaks do not push the file over the limit.
Typical bitrates
| Quality (H.264, 24–30 fps) | Video bitrate | Size per hour |
|---|---|---|
| 480p SD | 2.5 Mbps | 1.1 GB |
| 720p HD | 5 Mbps | 2.3 GB |
| 1080p Full HD | 8 Mbps | 3.6 GB |
| 1080p at 60 fps | 12 Mbps | 5.4 GB |
| 1440p QHD | 16 Mbps | 7.2 GB |
| 4K UHD | 40 Mbps | 18 GB |
Newer codecs need less: HEVC (H.265) and AV1 typically match H.264 quality at roughly 30–50% lower bitrate, which shrinks files by the same proportion.
What changes the bitrate you need
- Motion and detail. Sports, water, foliage and film grain need far more bits than a talking head on a plain background.
- Frame rate. Doubling from 30 to 60 fps usually needs 40–50% more bitrate, not 100%, because consecutive frames are similar.
- Constant vs. variable bitrate. CBR keeps the size exact; VBR spends bits where they help and averages to the target.
- Audio is small next to video at HD sizes but matters for low-bitrate or audio-only targets.
To estimate how long the finished file takes to upload, use the download time calculator with your upload speed, or the bandwidth calculator for streaming data use. For unit conversions such as GiB to GB, see the data storage converter.
Frequently asked questions
How do I calculate video file size from bitrate?
Add the video and audio bitrates, multiply by the duration in seconds and divide by 8 to get bytes. For 45 minutes at 8 Mbps video and 192 kbps audio: 8.192 × 10⁶ × 2,700 ÷ 8 = 2.76 GB, about 2.79 GB with 1% container overhead.
What bitrate do I need for a 2 GB file?
Divide the size in bits by the duration, then subtract the audio. For a 45-minute video: 2 × 10⁹ × 8 ÷ 1.01 ÷ 2,700 = 5.87 Mbps total, minus 0.192 Mbps of audio = about 5.68 Mbps for video.
How big is one hour of 4K video?
It depends entirely on the bitrate. At a typical 40 Mbps delivery bitrate it is about 18 GB per hour; a camera recording at 100 Mbps fills about 45 GB per hour, and professional intermediate codecs can exceed 300 GB per hour.
What is bits per pixel?
Video bitrate divided by pixels per second (width × height × frame rate). It normalizes bitrate across resolutions: around 0.05–0.1 is typical for streaming H.264, and more is needed for grain, fast motion or older codecs.