Video File Size Calculator (MB per minute, how much fits, shrink to a limit)
Pick a recording setting and a length to see the file size, then see how many minutes fit on your phone, or work out the bitrate that gets a clip under a size limit.
How big will my video be?
How much video fits in my free space?
Shrink it to fit a size limit
Work out the bitrate that lands a video just under a limit, with copy-ready ffmpeg two-pass commands. Your file never leaves your computer; this page only does the sums.
How it works
Pick a recording setting and a format, then type the length as minutes (12), mm:ss, h:mm:ss or words like 1h 20m. The size is MB = Mbps × seconds ÷ 8, so a 1080p 30 fps clip at about 8 Mbps is about 60 MB a minute. Choose Custom bitrate if you know your camera's exact rate.
The preset rates are typical rounded figures for phone cameras, not measurements of one model. HEVC (called High Efficiency on iPhone, H.265 elsewhere) stores the same picture in roughly half the space of H.264 (Most Compatible) at 4K, and about two-thirds at 1080p. Slow motion records many more frames, so it is large whatever the format.
Sizes are in decimal MB and GB, the way phones and drive boxes count. Windows shows GiB, which look about 7% smaller, so both are shown. The FAT32 note warns when one file would pass 4 GB, the largest file a FAT32 card or USB stick can hold. Cameras split the recording there; formatting the drive as exFAT avoids the limit.
How much fits turns your free space into recording time for every setting at once, longest bar first in the format you picked. On a phone, keep about 10% free so the system has room to work.
Shrink it to fit divides the limit by the length to get a total bitrate, keeps 3% headroom for the container and rate wobble, then takes away the audio. If the video bitrate is low for the size, the commands scale the picture down (720p, 480p or 360p), because a smaller sharp picture looks better than a full-size blocky one. Two-pass encoding lets ffmpeg spend bits where the video needs them while hitting the size closely. Run the commands on your own computer; nothing is uploaded here.
Background: how big a minute of video is, compress a video to a target size, how long a video takes to upload and the streaming data calculator for watching rather than recording. Need the same maths from a script or an upload form? Anvil's free video size API returns sizes, what fits and the target bitrate with ffmpeg commands as JSON, with no key.
Questions
How big is a 1 minute 4K video?
About 170 MB at 4K 30 fps in HEVC, and around 350 MB in H.264. 4K 60 fps HEVC is about 400 MB a minute.
How big is a minute of 1080p video?
About 40 MB at 1080p 30 fps in HEVC and 60 MB in H.264; 1080p 60 fps is about 60 to 90 MB.
How many minutes of 4K fit in 128 GB?
At 4K 30 fps HEVC, about 12 hours if the whole 128 GB were free; in practice the system and apps take some, so plan on less.
What bitrate do I need to get a 2 minute video under 25 MB?
About 1,490 kbps of video with 128 kbps audio, which looks best scaled to 720p. The tool works out any size and length.
Why does my camera split long videos into 4 GB files?
The card is probably FAT32, which can't hold a single file over 4 GB. Formatting it as exFAT removes the limit on cameras that support it.
Is my video uploaded?
No. The page only does arithmetic in your browser. You never select a file; the ffmpeg commands run on your own computer.