Calculating your estimated file size is straightforward once you know the Video File Size formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Video File Size Calculator.
What is Video File Size?
The Video File Size calculation tells you your estimated file size from a few simple inputs. The figure you are solving for here is the estimated file size.
The Video File Size formula
The core formula is:
Estimated file size = Bitrate × Duration ÷ 8Here is what each input means:
- Bitrate — a value measured in Mbps. Example: 5 Mbps.
- Duration — a value measured in seconds. Example: 600 seconds.
How to calculate it step by step
- Write down the bitrate (for example, 5 Mbps).
- Write down the duration (for example, 600 seconds).
- Apply the formula above to get your estimated file size.
- Double-check the result with the Video File Size Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Bitrate | 5 Mbps |
| Duration | 600 seconds |
| Estimated file size | 375.00 |
| In gigabytes | 0.366 |
With bitrate of 5 Mbps and duration of 600 seconds, the estimated file size works out to 375.00.
Example 2
With bitrate of 10 Mbps and duration of 600 seconds, the estimated file size works out to 750.00.
| Result | Value |
|---|---|
| Estimated file size | 750.00 |
| In gigabytes | 0.732 |
Example 3
With bitrate of 2.5 Mbps and duration of 600 seconds, the estimated file size works out to 187.50.
| Result | Value |
|---|---|
| Estimated file size | 187.50 |
| In gigabytes | 0.183 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Video File Size Calculator does it instantly, for free, with the formula and a worked example built in.
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