Video File Size
Calculator

File size equals bitrate (in bits per second) multiplied by duration in seconds, then divided by 8 to convert to bytes, the same underlying relationship used for audio files. A 10-minute video at 20 Mbps works out to roughly 1.5 GB.

Resolution alone doesn't determine file size, bitrate does, and bitrate is set independently based on desired quality, codec efficiency, and compression settings, so a 1080p video compressed aggressively at 5 Mbps will be much smaller than the same 1080p footage encoded at 50 Mbps for archival quality.

The codec doesn't change the basic bitrate-to-size math, but it does affect what bitrate is needed to achieve a given visual quality, since modern codecs like H.265/HEVC can deliver similar quality to older H.264 at roughly half the bitrate. So the calculator's output is exact for a given bitrate, but the 'right' bitrate to choose depends heavily on which codec you're using.

Higher resolution and frame rate mean there's more visual information to encode each second, so achieving the same perceived quality at 4K/60fps requires a substantially higher bitrate than at 1080p/30fps, even though the file-size formula itself only directly uses bitrate and duration. Resolution and frame rate influence what bitrate you should choose, not the formula itself.

Estimating file size in advance from your planned bitrate and shoot duration helps you budget storage capacity, memory card sizes, and upload/transfer times before you start recording, rather than discovering a card is full or an upload will take hours partway through a project.