How is video file size calculated from bitrate?

File size equals bitrate times duration. Bitrate is measured in megabits per second, so multiply by the number of seconds and divide by eight to get megabytes. A 100 Mbps clip for 60 seconds is 100 times 60 divided by 8, which is 750 megabytes.

What is the difference between megabits and megabytes?

Bitrate is quoted in megabits per second, written Mbps with a lowercase b. File size is in megabytes, written MB with an uppercase B. There are eight bits in a byte, so you always divide the bitrate figure by eight to convert to storage units.

Why are ProRes and RAW files so large?

Intra-frame and lightly compressed formats like ProRes 422 HQ and camera RAW store each frame nearly independently to preserve quality for editing. ProRes 422 HQ at 4K runs around 880 Mbps, while compressed delivery codecs like H.265 manage similar quality at a tenth of the bitrate.

How do I find the bitrate for a target file size?

Switch the tool to reverse mode and enter your target size and duration. It divides the size in megabits by the duration in seconds to give the bitrate. This is useful when fitting an export to an upload limit or a fixed card capacity.

Does frame rate change the file size?

Only indirectly. Most codecs are specified at a target bitrate that already assumes a frame rate, so higher frame rates usually carry a higher bitrate to keep quality constant. If you fix the bitrate, the file size depends only on bitrate and duration, not frame rate.

Video Bitrate & Storage Calculator

Cinema and high-bitrate codecs eat storage fast, and running out mid-take is expensive. This calculator converts any bitrate and recording length into a file size, reverse-solves the bitrate for a target size, and tells you how many minutes of footage your card or drive will hold.

How it works

Video file size is the simplest media calculation of all — it is just bitrate multiplied by time:

size (megabytes) = bitrate (Mbps) × duration (seconds) ÷ 8

The divide-by-eight converts megabits to megabytes. For a 100 Mbps clip running 60 seconds:

100 × 60 ÷ 8 = 750 MB.

To go the other way and find the bitrate for a target size:

bitrate (Mbps) = (size in MB × 8) ÷ duration (seconds)

Codec presets

The tool loads typical bitrates for common acquisition and delivery codecs:

Codec	Approx. bitrate
H.264 1080p (streaming)	8–16 Mbps
H.265 / HEVC 4K	50–100 Mbps
DSLR 4K (8-bit)	100 Mbps
ProRes 422 LT 4K	~410 Mbps
ProRes 422 HQ 4K	~880 Mbps
ProRes 4444 4K	~1320 Mbps
Blackmagic RAW 4K (12:1)	~290 Mbps

These are nominal figures; real bitrates vary with frame rate and scene complexity, but they are close enough for storage planning.

Notes and tips

Always carry overhead. Cards are sold in decimal gigabytes and the filesystem reserves a little, so budget about 10% headroom over the tool’s minutes figure.
Editing codecs are huge — a one-hour ProRes 422 HQ 4K shoot is roughly 380 GB. Transcode or use proxies for long projects.
Match bitrate to delivery. A 10-minute YouTube upload only needs 16 Mbps H.264; do not waste card space shooting it in RAW unless you need the grade.

All calculations run locally in your browser.