Video & Audio File Size Calculator
Estimate file size from bitrate and duration, or the bitrate to hit a size.
Last updated
Your details
Result
- Estimated file size
- 389.40 MB
- Total bitrate
- 5,192 kbps
- Per minute
- 38.94 MB
- Per hour
- 2.34 GB
0.389 GB · 371.36 MiB
Size is just bitrate times duration
File size in bits equals total bitrate multiplied by seconds. Divide by eight for bytes. Everything else — resolution, codec, frame rate — matters only insofar as it determines what bitrate you need for acceptable quality.
This is why a two-hour film at 5 Mbps and a two-hour film at 50 Mbps differ tenfold in size while both running the same length.
Choosing a bitrate
As rough guidance for H.264: 1080p at 30 fps looks good around 5 Mbps, 720p around 2.5 Mbps, and 4K needs 15–25 Mbps. Modern codecs like H.265 and AV1 achieve similar quality at roughly half the bitrate, at the cost of much slower encoding.
Content matters too. Fast motion, grain and rapid scene changes need far more bitrate than a static talking head at the same resolution.
Formula & methodology
What this calculator assumes
- Bitrates are quoted in bits per second and file sizes in bytes, so the division by eight is not optional. Sizes here use the decimal megabyte of 10⁶ bytes.
- Assumes constant bitrate. Variable-bitrate encoding, which is what most modern encoders do by default, produces a size that moves around this estimate with the difficulty of the material.
- Container overhead — the muxing, index and metadata around the streams — adds roughly one to two percent and is not included.
Sources
Frequently asked questions
Is variable bitrate more efficient?
Yes. VBR allocates more data to complex scenes and less to simple ones, giving better quality at the same average size. These estimates assume a constant average, which is what VBR targets anyway.
What bitrate do I need for 1080p or 4K?
As a rough guide, 8 to 12 Mbps for 1080p30 and 35 to 45 Mbps for 4K30 in H.264; H.265 and AV1 reach comparable quality at roughly half that. Frame rate matters as much as resolution — doubling to 60 fps adds around 50% rather than 100%, since successive frames are more similar.
Does audio count towards the file size?
Yes, and it is usually small enough to overlook until it is not. Stereo AAC at 128 to 256 kbps adds roughly 1 to 2 MB per minute, which is negligible against video but dominant for a podcast or an audio-only export.
Why is my exported file a different size?
Because the estimate assumes a constant average bitrate and the encoder does not deliver one exactly. Variable bitrate encoding targets the average over the whole clip, container overhead adds a small fixed cost, and a two-pass encode lands closer to the target than a single-pass one.