Video File Size Calculator
Enter the length and the video and audio bitrates to see how big the file will be. Or enter a size limit to find the bitrate that fits.
Type the limit of your app, email or upload form. The chips are just examples.
Typical example bitrates, not a standard: phones, cameras, codecs and services all differ. Edit the number to match your file (in VLC: Tools › Codec information; on a file: Properties › Details).
Use 0 for a silent video. 128 kbps is a common AAC stereo setting.
MP4, MKV and MOV files add a little for headers and indexes, roughly 1–2%. A rough guide only.
Extra languages or a commentary track each add the audio bitrate again.
Shows how long you can record at this bitrate. Cards are sold in decimal GB.
Best-case time to upload the file. Leave blank to skip.
Bitrate ≈ width × height × frames a second × bits per pixel. The bits-per-pixel figures are rough guesses; real encoders vary a lot with the scene and settings.
This length at typical example bitrates
| Example | Video + audio | File size | Binary |
|---|
How your video file size is worked out
Add the video and audio bitrates, multiply by the length in seconds, then turn bits into bytes.
- 1
Add the bitrates
8 Mbps + 128 kbps
= 8.128 Mbps - 2
Length in seconds
10 min 0 s
= 600 s - 3
Bitrate × time
8.128 × 600
= 4,876.8 Mbit - 4
Bits into bytes
4,876.8 ÷ 8
= 609.6 MB
Read more: the formula, a worked example, typical bitrates and MB vs MiB
A video's bitrate is how many bits it uses for each second of playback. Multiply that by the number of seconds and you have the size in bits; divide by 8 and you have bytes. The audio has its own bitrate, so add it on top of the video.
The formula
total bitrate = video bitrate + audio bitrate × number of audio tracks
file size (bytes) = total bitrate (bits a second) × length (s) ÷ 8 × (1 + overhead ÷ 100)
bitrate to fit = size limit × 8 ÷ (1 + overhead ÷ 100) ÷ length, then take off the audio
recording time (s) = card size × 8 ÷ (total bitrate × (1 + overhead ÷ 100))
camera estimate ≈ width × height × frames a second × bits per pixel
streaming GB per hour = total Mbps × 3,600 ÷ 8 ÷ 1,000 = Mbps × 0.45
Worked example
A 10 minute video at 8 Mbps with 128 kbps audio. The total bitrate is 8 + 0.128 = 8.128 Mbps. The length is 10 × 60 = 600 s. Bits: 8.128 × 600 = 4,876.8 megabits. Bytes: 4,876.8 ÷ 8 = 609.6 MB. In binary units that is 609,600,000 ÷ 1,048,576 = 581.36 MiB, which Windows shows as “581 MB”.
With 1% container overhead (Advanced) it becomes 609.6 × 1.01 = 615.696 MB, about 615.7 MB.
The other way round: to fit the same 10 minutes under 100 MB, turn the limit into bits, 100 × 8 = 800 megabits, and divide by 600 s: 1.3333 Mbps in all. Take off 0.128 Mbps of audio and the video can use about 1.2053 Mbps (1,205 kbps). Encoders often overshoot a little, so aim a few percent lower.
On a 64 GB card (512,000 megabits) at 8.128 Mbps you can record 512,000 ÷ 8.128 = 62,992 s, about 17 h 29 min 52 s. Streaming at 8.128 Mbps uses 8.128 × 0.45 = 3.6576 GB an hour, and uploading the 609.6 MB file at 20 Mbps takes 4,876.8 ÷ 20 = 243.84 s, about 4 min 4 s.
Typical example bitrates
These are ballpark figures for common H.264 or H.265 files and recordings, not a standard. Streaming services use less; cameras recording for editing use much more.
| Quality | Typical example | About per hour |
|---|---|---|
| 480p | ~2.5 Mbps | 1.1 GB |
| 720p | ~5 Mbps | 2.25 GB |
| 1080p | ~8 Mbps | 3.6 GB |
| 1440p | ~16 Mbps | 7.2 GB |
| 4K | ~35–45 Mbps | 15.75–20.25 GB |
Bits, bytes, MB and MiB
Bitrates are in bits a second (small b: kbps, Mbps) and count in 1000s: 1 Mbps = 1,000 kbps = 1,000,000 bits a second. File sizes are in bytes (big B), and 1 byte = 8 bits. Decimal sizes count in 1000s (1 MB = 1,000,000 bytes); binary sizes count in 1024s (1 MiB = 1,048,576 bytes, 1 GiB = 1,073,741,824 bytes). Windows uses 1024s but writes “MB”, so files look about 5% smaller there than on a Mac or phone at the MB level and about 7% smaller at the GB level.
Why the real file may differ
Most videos use a variable bitrate: quiet, still scenes use fewer bits and busy, fast scenes more. The bitrate a file reports is an average, so the sum gives the average size. The container (MP4, MOV, MKV) adds a little for headers and the index, roughly 1–2%. Cards and drives also lose a little space to the file system, so recording times are best case.
The camera estimate
Bits per pixel (bpp) is how many bits the encoder spends on each pixel of each frame. 1080p at 30 fps is 1,920 × 1,080 × 30 = 62,208,000 pixels a second; at a rough 0.1 bpp that is 6,220,800 bits a second, about 6.22 Mbps. Newer codecs such as H.265 and AV1 need fewer bits for the same look; edit codecs such as ProRes use many more. Treat this only as a starting guess and use your camera's stated bitrate if you have it.
Example bitrates and bits-per-pixel figures are rough starting points, not figures for any specific product or service. Units follow IEC 80000-13. Checked 13 October 2026.
Common questions
How do I work out a video file size from its bitrate?
Add the video and audio bitrates, multiply by the length in seconds and divide by 8 to turn bits into bytes. A 10 minute video at 8 Mbps with 128 kbps audio is 8.128 Mbps × 600 s = 4,876.8 megabits, and 4,876.8 ÷ 8 = 609.6 MB.
What bitrate do I need to fit a video under a size limit?
Turn the limit into bits, divide by the length in seconds, then take off the audio. To fit 10 minutes into 100 MB: 100 × 8 = 800 megabits, ÷ 600 s = 1.333 Mbps in all, minus 0.128 Mbps of audio leaves about 1.2 Mbps for the video. Aim a little lower, as encoders often overshoot a bit.
How much space does 1 hour of 1080p or 4K video take?
It depends on the bitrate, not the resolution alone. At a typical example 8 Mbps, one hour of 1080p is about 8 × 0.45 = 3.6 GB. At a typical 40 Mbps, an hour of 4K is about 18 GB. Phones and cameras range widely, so check the bitrate your device uses.
Why does my computer show a smaller size than the calculator?
Windows counts in 1024s but still writes “MB” and “GB”. 609.6 MB (decimal) is 609,600,000 ÷ 1,048,576 = 581.4 MiB, which Windows shows as 581 MB. The calculator shows both.
How long can I record on a 64 GB card?
Divide the card size in bits by the bitrate. 64 GB is 512,000 megabits; at a 40 Mbps 4K setting plus 128 kbps audio that is 512,000 ÷ 40.128 = 12,759 seconds, about 3 h 33 min. Some of the card is used by the file system, so expect a little less.
How much data does streaming video use per hour?
Multiply the bitrate in Mbps by 0.45 to get GB per hour. About 5 Mbps uses 2.25 GB an hour and about 16 Mbps uses 7.2 GB an hour. Services change their bitrates, so treat these as rough guides.
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