Video file size calculator

This video file size calculator takes the resolution bitrate in megabits per second, the frame rate in frames per second, the duration in seconds, and the audio bitrate in kilobits per second, then returns the encoded payload in megabytes or gigabytes so you can size disks, upload quotas, and YouTube drafts before you hit record. Duration must be a positive finite number; zero, negatives, NaN, and Infinity fail with invalid_input and are not billed. The solver reports size_mb using SI megabytes of one million bytes, size_gb using SI gigabytes of one billion bytes, and a primary size with size_unit that switches to GB at one gigabyte. Frame count and bits per frame come from frame_rate so you can sanity-check a 24p versus 60p timeline at the same bitrate.

How encoded video file size is estimated from bitrates

The payload in bytes is therefore the sum of video bits per second and audio bits per second, multiplied by duration, divided by eight because there are eight bits in a byte. Dividing that byte count by one million yields size_mb; dividing by one billion yields size_gb. When the payload is at least one gigabyte the primary size field reports gigabytes and size_unit is GB, otherwise it reports megabytes. Frame rate does not change the bitrate-times-time product, but it tells you how many pictures that budget is spread across: bits_per_frame is video_bitrate in bits per second divided by frame_rate, and frame_count is frame_rate times duration.

Input contract, units, and response fields

POST a JSON body with four required finite numbers: video_bitrate in megabits per second, frame_rate in frames per second, duration in seconds, and audio_bitrate in kilobits per second. Aliases are accepted so common synonyms still work: resolution_bitrate, bitrate, video_mbps, mbps, and video_bitrate_mbps for video_bitrate; fps, frames_per_second, framerate, and frame_rate_fps for frame_rate; duration_seconds, seconds, length, and time for duration; audio_kbps, audio, aac_kbps, and audio_bitrate_kbps for audio_bitrate. Each field may arrive as a JSON number or as a numeric string. Duration must be a positive finite number: missing duration, empty strings, zero, negatives, NaN, and Infinity fail with invalid_input naming duration and are not billed. video_bitrate and frame_rate must also be positive finite numbers so bits_per_frame is defined. audio_bitrate must be a non-negative finite number; zero is allowed for a video-only estimate. There is no enum on frame_rate because the contract is any positive rate, including twenty-three point nine seven six and twenty-nine point nine seven, not a closed list of broadcast presets. On success the body echoes the four inputs, total_bitrate_kbps and total_bitrate_mbps, frame_count, bits_per_frame, bytes_per_frame, video_size_bytes, audio_size_bytes, size_bytes, size_mb, size_gb, size_mib, size_gib, the primary size and size_unit, plus formula and note strings. Example: video_bitrate 8, frame_rate 30, duration 60, audio_bitrate 128 returns 60.96 in size_mb with size_unit MB. Pair the response with your own encoder if you need a content-dependent VBR guess; this endpoint reports the constant-bitrate size from the rates you already chose.

Where a video file size calculator earns its keep

Educators teaching digital video show that doubling duration doubles file size when bitrates stay fixed, and that raising frame_rate at a fixed bitrate shrinks bits per frame rather than growing the file, which this calculator makes immediate. Backup and ingest scripts can reject a planned encode that would exceed an object-store quota by computing size_mb or size_gb first.