Video File Size Calculator
Estimate a video file's size.
Result
How it is calculated
The tool assumes a constant bitrate. Size in megabytes is MB = bitrate × duration × 60 ÷ 8, where bitrate is in megabits per second (Mbps) and duration is in minutes. Multiplying by 60 converts minutes to seconds, giving total megabits; dividing by 8 turns bits into bytes. Gigabytes are then GB = MB ÷ 1,000, the same decimal base as the MB figure. Both inputs must be above zero. The estimate covers the video stream alone as you describe it; audio tracks, subtitles and container overhead are not added, and variable-bitrate encodes will land above or below the result.
Worked example
A 90-minute film is encoded at 8 Mbps. Total seconds = 90 × 60 = 5,400. Total data = 8 × 5,400 = 43,200 megabits. Divide by 8 to get bytes: 43,200 ÷ 8 = 5,400.00 MB. In gigabytes, 5,400 ÷ 1,000 = 5.40 GB. So the film needs about 5.4 GB of storage before audio is added. Doubling the bitrate to 16 Mbps would double both numbers, since size grows in direct proportion to bitrate.
Common mistakes
- Entering the duration in seconds or hours. The field is minutes, so a two-hour film must be typed as 120; typing 2 shows a file that is 60 times too small.
- Mixing up megabits and megabytes. An 8 Mbps stream moves 1 megabyte per second; entering 8 as if it were MB/s overstates the size by 8 times.
- Entering the bitrate in kbps. A 5,000 kbps file is 5 Mbps; typing 5000 gives a result 1,000 times too large.
- Forgetting audio. A typical audio track adds its own bitrate, so for a precise total, add the audio bitrate to the video bitrate before using this tool.
- Assuming a variable-bitrate export will match. VBR files vary with scene complexity, so treat the answer as an average-case estimate.
About this calculator
This calculator estimates a video file's size as bitrate × duration, converting the result from bits to bytes (dividing by 8) and then to megabytes or gigabytes. Bitrate measures how much data is encoded per second of footage, and it varies enormously by resolution and codec: streaming platforms typically recommend around 8 Mbps for 1080p and 35–45 Mbps for 4K, while variable bitrate (VBR) encoding — common in modern codecs like H.264 and H.265 — allocates more data to complex, high-motion scenes and less to static ones, so actual file size can differ from a constant-bitrate estimate.
Video editors and YouTubers use this to estimate upload sizes and plan render/export settings, videographers use it to figure out how much footage fits on an SD card or drive before a shoot, and streaming and broadcast engineers use similar math to set encoding presets that balance quality against bandwidth.
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Comments (1)
The gigabyte figure uses 1000 megabytes, the same way memory cards are labelled, while many computers report storage in binary units and show a smaller number. A 128 GB card therefore holds roughly 28 hours at the preset 10 Mbps video stream, and a bit less once audio is added. Plan with some margin rather than filling a card to the last minute. What bitrate and card size do you record with?