OneTaskBy Tim King · Updated
Video File Size Estimator
Estimate Size From Video and Audio Bitrates, With a Per-Minute and Per-Hour Table
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How the Video File Size Estimator works
This video file size estimator tells you how large a recording or export will be before you make it. Enter the length, the video bitrate and the audio bitrate, and it shows the total file size, the share taken by each stream and a table of sizes at common bitrates.
Bitrate is the amount of data a video uses each second. Once you know the bitrate and the length, the file size follows directly, whatever the codec or resolution. That makes it easy to plan card space for a shoot, check an export will fit under an upload limit, or budget cloud storage.
The video file size estimator formula
The formula is: size in bytes = (video bitrate + audio bitrate) × duration in seconds ÷ 8. Bitrates are in bits per second, and dividing by 8 turns bits into bytes. Sizes here use decimal units, so 1 MB is 1,000,000 bytes and 1 GB is 1,000 MB, as drive makers and most upload forms count them.
Worked example, a YouTube export: 10 minutes at 8 Mbit/s video and 128 kbit/s audio is 8.128 Mbit/s × 600 s ÷ 8 = 609.6 MB.
Worked example, a camera card: 1 hour of 4K at 100 Mbit/s is 100 × 3,600 ÷ 8 = 45,000 MB, or 45 GB. A 128 GB card holds about 2 hours 50 minutes.
How many minutes fit on a drive? Divide the drive size by the per-minute figure in the result. The table shows sizes per minute, per hour and for your duration at 22 common bitrates.
File size by video bitrate, excluding audio
| Bitrate | Typical use | Per minute | Per hour |
|---|---|---|---|
| 0.5 Mbit/s | 360p web preview | 3.8 MB | 225 MB |
| 1 Mbit/s | 480p web video | 7.5 MB | 450 MB |
| 1.5 Mbit/s | Low-bandwidth 720p | 11.3 MB | 675 MB |
| 2 Mbit/s | Video call, 720p | 15 MB | 900 MB |
| 2.5 Mbit/s | 480p upload | 18.8 MB | 1.13 GB |
| 3 Mbit/s | 720p stream | 22.5 MB | 1.35 GB |
| 4 Mbit/s | 720p60 stream | 30 MB | 1.8 GB |
| 5 Mbit/s | 720p upload | 37.5 MB | 2.25 GB |
| 6 Mbit/s | 1080p stream | 45 MB | 2.7 GB |
| 8 Mbit/s | 1080p upload | 60 MB | 3.6 GB |
| 10 Mbit/s | Screen recording, 1080p | 75 MB | 4.5 GB |
| 12 Mbit/s | 1080p60 upload | 90 MB | 5.4 GB |
| 15 Mbit/s | 1440p upload | 112.5 MB | 6.75 GB |
| 16 Mbit/s | Phone 1080p30 | 120 MB | 7.2 GB |
| 20 Mbit/s | Phone 1080p60 | 150 MB | 9 GB |
| 25 Mbit/s | Blu-ray average | 187.5 MB | 11.25 GB |
| 35 Mbit/s | 4K upload | 262.5 MB | 15.75 GB |
| 45 Mbit/s | Phone 4K30 | 337.5 MB | 20.25 GB |
| 50 Mbit/s | Camera 1080p | 375 MB | 22.5 GB |
| 68 Mbit/s | 4K60 upload | 510 MB | 30.6 GB |
| 100 Mbit/s | Camera 4K | 750 MB | 45 GB |
| 150 Mbit/s | Camera 4K 10-bit | 1.13 GB | 67.5 GB |
Tips and pitfalls
Variable bitrate is an average. Most phones and encoders change bitrate with the scene. A calm talking head comes in under the target and fast action goes over, so real files vary by 10–20%.
Container overhead is small. MP4 and MKV headers add well under 1%, so they are ignored here.
MiB versus MB. Windows shows sizes in binary units, where 1 GB on screen is 1,073,741,824 bytes. A 4.7 GB file can appear as 4.37 GB there.
How to read the result
The estimated size is the whole file. The stream lines show how much is picture and how much is sound, and the per-minute figure helps when you trim or extend the clip.
FAQ
How big is a 1 hour 1080p video?
It depends on the bitrate. At a typical 8 Mbit/s upload bitrate it is about 3.6 GB, plus around 58 MB for 128 kbit/s audio. A phone recording at 20 Mbit/s is about 9 GB for the same hour.
Does resolution change the file size?
Only through the bitrate. A 4K and a 720p file at the same bitrate are the same size, but the 4K one will look worse because each pixel gets less data. That is why higher resolutions use higher bitrates.
How do I find a video's bitrate?
Divide the file size in bits by its length in seconds, or use a video info inspector, which reads both from the file and shows the average bitrate. Editors also show the target bitrate in their export settings.
Why is my exported file a different size?
Encoders usually treat the bitrate as an average or a cap, not an exact value. Simple scenes need fewer bits, so the file is often smaller. Two-pass and constant-bitrate exports land closest to the estimate.
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