Calculate how large your video file will be from bitrate and duration — or find the bitrate you need to hit a storage target.
Estimated file size
304.80 MB
Duration
300 s
Calculator
Estimated file size
304.80 MB
Total bitrate
8,128 kbps
Audio
128 kbps
Duration
300 s
Storage comparison by quality tier
Fits on 64 GB card
How video file size is calculated
A video file's size is determined by its total bitrate (video + audio) multiplied by duration. The formula is: bytes = (videoBitrateKbps + audioBitrateKbps) × 1000 bits/s × durationSeconds ÷ 8. We use SI kilobits (1 kbps = 1000 bits/s), which matches industry standards like H.264 and YouTube's recommended encoding settings.
Resolution and frame-rate presets use YouTube's recommended upload bitrates as a starting point: 720p30 ≈ 5 Mbps, 1080p30 ≈ 8 Mbps, 1080p60 ≈ 12 Mbps, 4K30 ≈ 35–45 Mbps. Your actual bitrate may differ depending on your encoder, content complexity and target quality.
Why does the same resolution produce different file sizes?
File size depends on bitrate, not just resolution. A 1080p video encoded at 4 Mbps will be half the size of one at 8 Mbps with the same duration. Resolution is one factor that influences the recommended bitrate, but you can always encode at a lower or higher bitrate for the same resolution.
What audio bitrate should I use?
128 kbps AAC is a common default for stereo audio online. 192–320 kbps suits music or audiophile content. Live streams and podcasts often use 96–128 kbps. Audio is typically a small fraction of a video file's total bitrate.
What is the difference between kbps and Mbps?
1 Mbps = 1000 kbps. Both measure data rate in the same base (SI kilobits). A 4K video at 40 Mbps is 40,000 kbps. This calculator accepts both units — pick whichever is easier for your workflow.
Results are estimates. Verify with a professional for important decisions.
About this calculator
This calculator estimates how much storage space a video will occupy, or works backwards to find the bitrate you need to hit a target file size. Use it to plan uploads, compare storage requirements across resolutions, or decide how to encode a project before committing to a format.
How to read your results
The headline figure is the estimated file size in megabytes or gigabytes. When you enter a video bitrate, an audio bitrate, and a duration, the tool multiplies the total bitrate by the duration and divides by 8 to convert bits into bytes. Switch to "find bitrate" mode to solve in reverse — enter a target size and duration, and the calculator returns the maximum video bitrate you can use.
Worked example
A 1080p video encoded at 8,000 kbps (video) plus 192 kbps (audio) runs for 10 minutes (600 seconds).
Total bitrate is 8,192 kbps. File size = 8,192 × 1,000 × 600 ÷ 8 = 614,400,000 bytes, which the calculator displays as 614.40 MB.
Frequently asked questions
Why does this calculator use 1,000 bits per kilobit instead of 1,024?
Video bitrates are defined in SI (decimal) kilobits — 1 kbps = 1,000 bits per second — following the ITU-T H.264 standard and platform specs like YouTube. Hard-drive capacities also use decimal prefixes, so the formula stays consistent with both.
Does a higher resolution automatically mean a larger file?
Resolution alone does not determine file size — bitrate and duration do. However, higher resolutions (1080p, 4K) require a higher bitrate to look good, so they indirectly lead to larger files when quality is held constant. A 4K clip encoded at a very low bitrate can be smaller than a high-quality 720p clip.
What is the difference between constant bitrate and variable bitrate?
Constant bitrate (CBR) keeps the data rate fixed for every second of video, making file size easy to predict. Variable bitrate (VBR) allocates more bits to complex scenes and fewer to simple ones, producing better quality at the same average file size. This calculator uses the average bitrate you enter, so it gives accurate estimates for CBR and good approximations for VBR.
Does audio bitrate make a big difference to total file size?
For most video, audio is a small fraction of the total. A 192 kbps stereo track on a 10-minute clip adds about 14 MB — significant for very short clips or low-bitrate video, but minor against a 600 MB high-definition file.
How do streaming platforms affect the actual file size after upload?
Platforms like YouTube re-encode every upload to their own target bitrates, so the file your viewers stream will differ from what you uploaded. Use this calculator to plan your source file and upload budget, not to predict the platform’s output size.
How it's calculated
File size in bytes equals the total bitrate in kilobits per second multiplied by 1,000 to convert to bits per second, then multiplied by the duration in seconds, then divided by 8 to convert bits to bytes. Total bitrate is the sum of video bitrate and audio bitrate, both expressed in kbps using the SI decimal convention where 1 kbps equals exactly 1,000 bits per second. Higher resolution and higher frame rates require a higher bitrate to maintain perceived quality, so they indirectly increase file size when quality is held constant. Constant bitrate encoding fills every second at the same rate, making the formula exact. Variable bitrate encoding fluctuates around an average, so the result is an approximation based on the average bitrate entered.
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