tech calculator

Video File Size & Bitrate Calculator

Estimate video file size from bitrate and duration, or find the bitrate that fits a target file size.

Video File Size (bytes) = (Video kbps + Audio kbps) × 1,000 × seconds × (1 + container overhead) ÷ 8. Example: one hour at 10 Mbps with 192 kbps audio and 2% overhead is 4,678,128,000 bytes — 4.678 GB, shown as 4.357 GiB by a file browser.

Formula Verified by Dr. James Callahan, PhD

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Mode

Hours

Minutes

Seconds

Video BitrateMbps

Audio Bitratekbps

Container Overhead%

Results

File Size (decimal GB)

4.678 GB

File Size (binary GiB, as your OS shows it)4.357 GiB

File Size in MB4678.1 MB

Total Bitrate10.192 Mbps (10192 kbps)

Duration3,600 seconds

Exact Bytes4,678,128,000

Tip

Worth keeping for every export: sizing a memory card, checking an upload limit, or picking a bitrate that fits a delivery spec.

Formula

Video file size and bitrate formulas

Total Bitrate (kbps) = Video Bitrate + Audio Bitrate
File Size (bytes) = Total Bitrate × 1,000 × Duration (s) × (1 + Overhead) ÷ 8
File Size (GB)  = bytes ÷ 1,000,000,000     (decimal — what encoders quote)
File Size (GiB) = bytes ÷ 1,073,741,824     (binary — what your OS shows)

Target-size mode:
Total Bitrate (kbps) = Target Size (GB) × 8,000,000,000 ÷ (1 + Overhead) ÷ Duration (s) ÷ 1,000
Video Bitrate = Total Bitrate − Audio Bitrate

File size is bitrate multiplied by time, converted from bits to bytes by dividing by 8. Audio is added to the video bitrate before the conversion, because a container carries both streams. The two size units are the same file expressed against different powers: 1 GB is 10⁹ bytes and 1 GiB is 2³⁰, a 7.4% difference, which is why a file an encoder reports as 4.68 GB shows up as 4.36 GB in a file browser.

Step by step

How the calculation works

1Enter the clip length in hours, minutes, and seconds, then the video bitrate your encoder is set to. Bitrate is the entire story: file size is directly proportional to it, so doubling the bitrate doubles the file for the same running time. Resolution and frame rate only matter through the bitrate you need to keep them looking acceptable.
2Audio is entered separately in kbps because encoders configure it separately — 128 kbps for stereo AAC, 192 to 256 kbps for higher quality, 384 kbps and up for multichannel. It is small next to video but not negligible over a long recording.
3Container overhead covers muxing, index tables, and metadata that a container file adds on top of the raw audio and video streams. Around 2% is a reasonable default for MP4 or MKV; set it to zero if you want the pure elementary-stream arithmetic.
4Switch to target-size mode to invert the calculation: enter the file size you have to fit inside — an upload limit, a disc, a memory card — and the calculator returns the video bitrate that lands on it after reserving room for audio and overhead.
5Two related tools: the [data storage calculator](/calculators/data-storage-calculator) sizes a whole media library once you know what one file costs, and the [bandwidth calculator](/calculators/bandwidth-calculator) turns the same bitrate figure into the connection speed needed to stream it rather than store it.

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Tech Tool

Data Storage Calculator

Scale one file size up into a whole photo and video library in GB or TB.

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Bandwidth Calculator

Convert a bitrate into the connection speed needed to stream it, including concurrent viewers.

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Download Time Calculator

Find out how long the file you just sized takes to transfer at a given connection speed.

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Screen Resolution & PPI Calculator

Check the pixel density of the display you are capturing or delivering for.

tech calculator

Video File Size & Bitrate Calculator

Estimate video file size from bitrate and duration, or find the bitrate that fits a target file size.

Formula Verified by Dr. James Callahan, PhD

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Mode

Hours

Minutes

Seconds

Video BitrateMbps

Audio Bitratekbps

Container Overhead%

Results

File Size (decimal GB)

4.678 GB

File Size (binary GiB, as your OS shows it)4.357 GiB

File Size in MB4678.1 MB

Total Bitrate10.192 Mbps (10192 kbps)

Duration3,600 seconds

Exact Bytes4,678,128,000

Tip

Worth keeping for every export: sizing a memory card, checking an upload limit, or picking a bitrate that fits a delivery spec.

Summary

Key output metrics

File Size

4.68 GB

4.36 GiB as your operating system reports it

Total Bitrate

10.192 Mbps

10 Mbps video + 192 kbps audio

Size in MB

4678 MB

60.0 minutes of footage

D3 visualization

File Size by Video Bitrate (this duration)

How the same clip length scales across common encoding bitrates, in decimal GB. File size is directly proportional to bitrate — double the bitrate, double the file.

Guide

How to understand and use this calculator

Quick Answer — How Do You Calculate Video File Size?

File size is bitrate multiplied by duration, converted from bits to bytes: Size (bytes) = ((Video kbps + Audio kbps) × 1000 × seconds × (1 + overhead))/8. The division by 8 is the whole trick — bitrate is quoted in bits per second, file sizes in bytes.

Worked example: one hour at 10 Mbps video with a 192 kbps audio track and 2% container overhead. Total bitrate = 10,192 kbps. Size = 10,192 × 1,000 × 3,600 × 1.02 ÷ 8 = 4,678,128,000 bytes = 4.678 GB — which your file browser will display as 4.357 GiB.

One hour of footage with a 128 kbps audio track and 2% overhead, at common encoding bitrates:

1.5 Mbps (720p streaming) — 0.747 GB / 0.696 GiB
3 Mbps (1080p streaming) — 1.436 GB / 1.337 GiB
5 Mbps (good 1080p) — 2.354 GB / 2.192 GiB
8 Mbps (1080p high quality) — 3.731 GB / 3.475 GiB
10 Mbps (4K streaming) — 4.649 GB / 4.329 GiB
20 Mbps (4K high quality) — 9.239 GB / 8.604 GiB
50 Mbps (camera master) — 23.009 GB / 21.429 GiB

Resolution and frame rate never enter the formula directly. They matter only because they determine what bitrate the footage needs to look acceptable — a 4K clip encoded at 3 Mbps produces exactly the same file size as a 720p clip at 3 Mbps, and looks considerably worse.

How to Use This Calculator: Sizing a One-Hour Export

Enter the running time as hours, minutes, and seconds, then the video bitrate your encoder is configured for. For a one-hour export at 10 Mbps with 192 kbps AAC audio and 2% container overhead:

Total bitrate = 10,000 + 192 = 10,192 kbps, or 10.192 Mbps. Raw stream bits = 10,192 × 1,000 × 3,600 = 36,691,200,000. Adding 2% container overhead gives 37,425,024,000 bits, and dividing by 8 gives 4,678,128,000 bytes.

That is 4,678.13 MB, 4.678 GB in the decimal units encoders and drive manufacturers use, and 4.357 GiB in the binary units your operating system reports. All three describe the identical file. The audio track contributes about 88 MB of that total — small, but not nothing over an hour.

The bar chart on this page recalculates the same duration across a range of bitrates, which makes the proportionality obvious: file size tracks bitrate exactly, so halving the bitrate halves the file.

A Second Example: Working Backwards from an Upload Limit

Target-size mode inverts the formula, which is what you actually need when a platform imposes a hard ceiling. Say you have a 90-minute film to fit inside a 25 GB limit, with a 256 kbps audio track and 2% container overhead.

Total bitrate budget = 25 GB × 8,000,000,000 bits ÷ 1.02 ÷ 5,400 seconds ÷ 1,000 = 36,310.8 kbps. Subtract the 256 kbps reserved for audio and the video bitrate that lands on the target is 36,054.8 kbps, or 36.05 Mbps.

Feed 36.05 Mbps back into size mode with the same duration and audio and you get 25 GB back, which is the check worth doing whenever a delivery spec and an encoder disagree. Note how generous that budget is — 36 Mbps is well above streaming bitrates, so a 25 GB ceiling on a 90-minute film is not a real constraint at 1080p. Halve the duration to 45 minutes and the same 25 GB allows roughly twice the bitrate.

Why Your File Browser Disagrees With Your Encoder

A gigabyte has two meanings. Encoders, storage vendors, and this calculator's GB figure use the decimal definition: 1 GB = 1,000,000,000 bytes. Windows and most file browsers use the binary definition — 1,073,741,824 bytes — while still writing the label "GB". The binary unit holds 7.4% more bytes, so the same file reads about 7% smaller when measured that way: the 4,678,128,000-byte export above is 4.678 GB decimal and 4.357 GiB binary.

This is not rounding error, and neither number is wrong. It is why a "32 GB" memory card shows as roughly 29.8 GB when you insert it, and why an export that a spec sheet says fits a 25 GB limit can be rejected by a system measuring in binary units. This calculator returns both so you can check against whichever definition the receiving system uses.

The other reason a real file differs from the estimate is variable bitrate. Most modern encoders vary bitrate scene by scene and target an average rather than holding a constant rate, so the number you configure is a target the encoder aims at, not a guarantee. Constant-bitrate encoding matches this arithmetic almost exactly; variable-bitrate output typically lands within a few percent of it, and constant-quality modes (CRF and similar) can miss it by a wide margin because they do not target a bitrate at all.

Once you know what a single file costs, the data storage calculator scales it into a whole library, and the bandwidth calculator converts the same bitrate into the connection speed needed to stream it live rather than store it.

Limitations

This calculator performs exact arithmetic on the bitrate, duration, audio rate, and overhead you enter. It cannot tell you what bitrate your footage actually needs — that depends on resolution, frame rate, codec efficiency, and how much motion and detail the content contains. A static interview at 1080p looks fine at a bitrate that would make an action sequence at the same resolution fall apart.

It assumes a fixed average bitrate across the whole clip. Variable-bitrate and constant-quality encoding modes will land near this figure but not on it, and two-pass encodes that target a file size directly will be closer than single-pass constant-quality ones. Container overhead is modelled as a flat percentage, whereas real overhead varies with the container format, keyframe interval, chapter and subtitle tracks, and embedded metadata or thumbnails.

Newer codecs change the picture entirely and are outside the arithmetic: H.265 and AV1 typically deliver comparable quality to H.264 at roughly half the bitrate, so the right input for the same footage differs by codec. And nothing here accounts for multiple audio tracks, subtitle streams, or the extra copies a workflow generates — proxies, intermediate renders, and backups often outweigh the master file in total storage.

Related Calculators

The Data Storage Calculator turns a per-file size into a whole photo and video library in GB or TB, which is the natural next step once you have sized one export. The Bandwidth Calculator converts the same bitrate figure into the connection speed required to stream rather than store, including concurrent viewers. The Download Time Calculator tells you how long a file of this size takes to transfer at a given speed, and the Screen Resolution PPI Calculator covers the pixel density of the display you are capturing or delivering for. And if you are weighing a different codec or archive format, the Compression Ratio Calculator converts between compression ratio and space saved, and prices the storage and transfer time the difference actually buys.

Related concepts

Bitrate

The data rate of a video stream in kilobits or megabits per second. File size is directly proportional to it: double the bitrate, double the file for the same running time.

Decimal GB vs Binary GiB

1 GB is 10⁹ bytes (encoders, drive vendors); 1 GiB is 2³⁰ bytes (file browsers, still labelled GB). The binary unit holds 7.4% more, so the same file reads about 7% smaller in a file browser.

Container Overhead

The muxing structure, index tables, and metadata an MP4 or MKV file adds on top of the raw audio and video streams — typically around 2% of total size.

Frequently Asked Questions

How do I calculate video file size from bitrate?+

Multiply the total bitrate in kbps by 1,000 and by the duration in seconds to get bits, then divide by 8 for bytes. One hour at 10 Mbps video plus 192 kbps audio with 2% container overhead comes to 4,678,128,000 bytes — 4.678 GB, or 4.357 GiB as a file browser reports it.

How big is one hour of 1080p video?+

It depends entirely on bitrate. At 3 Mbps (typical 1080p streaming) an hour is about 1.44 GB; at 5 Mbps about 2.35 GB; at 8 Mbps about 3.73 GB. Camera masters at 50 Mbps reach roughly 23 GB per hour. Resolution alone does not determine size — bitrate does.

Why does my video file show a smaller size than this calculator says?+

Almost certainly the decimal versus binary gigabyte. Encoders and this calculator's GB figure use 1 GB = 10⁹ bytes; file browsers use 2³⁰ bytes while still labelling it GB. The same file reads about 7% smaller that way, which is why 4.678 GB appears as 4.357 GiB. This calculator shows both.

What bitrate do I need for a specific file size?+

Switch to target-size mode. The formula is target size in GB × 8,000,000,000 ÷ (1 + overhead) ÷ duration in seconds ÷ 1,000, minus the audio bitrate. A 90-minute film fitting 25 GB with 256 kbps audio and 2% overhead allows a video bitrate of 36.05 Mbps.

Does resolution affect file size?+

Not directly. A 4K clip and a 720p clip encoded at the same bitrate for the same duration produce identical file sizes — the 4K one just looks much worse. Resolution matters because it determines the bitrate the footage needs to look acceptable, not because it enters the size formula.

How much does the audio track add?+

Less than most people expect, but enough to matter over long recordings. A 192 kbps stereo track over one hour is about 88 MB — roughly 2% of a 10 Mbps video file, but a much larger share of a low-bitrate export. Multichannel tracks at 384 kbps and above roughly double that.

What is container overhead and what value should I use?+

It is the muxing structure, index tables, and metadata a container file adds on top of the raw audio and video streams. Around 2% is a reasonable default for MP4 or MKV. Set it to 0% if you want the pure elementary-stream arithmetic, or higher if the file carries multiple subtitle tracks, chapters, or embedded artwork.

Will H.265 or AV1 change the answer?+

Yes, but through the bitrate you enter rather than the formula. H.265 and AV1 typically match H.264 quality at roughly half the bitrate, so the same footage needs a much lower input to look the same — and at half the bitrate the file is half the size. The arithmetic is codec-independent; the appropriate bitrate is not.

Formula

Video file size and bitrate formulas

Total Bitrate (kbps) = Video Bitrate + Audio Bitrate
File Size (bytes) = Total Bitrate × 1,000 × Duration (s) × (1 + Overhead) ÷ 8
File Size (GB)  = bytes ÷ 1,000,000,000     (decimal — what encoders quote)
File Size (GiB) = bytes ÷ 1,073,741,824     (binary — what your OS shows)

Target-size mode:
Total Bitrate (kbps) = Target Size (GB) × 8,000,000,000 ÷ (1 + Overhead) ÷ Duration (s) ÷ 1,000
Video Bitrate = Total Bitrate − Audio Bitrate

Step by step

How the calculation works

1Enter the clip length in hours, minutes, and seconds, then the video bitrate your encoder is set to. Bitrate is the entire story: file size is directly proportional to it, so doubling the bitrate doubles the file for the same running time. Resolution and frame rate only matter through the bitrate you need to keep them looking acceptable.
2Audio is entered separately in kbps because encoders configure it separately — 128 kbps for stereo AAC, 192 to 256 kbps for higher quality, 384 kbps and up for multichannel. It is small next to video but not negligible over a long recording.
3Container overhead covers muxing, index tables, and metadata that a container file adds on top of the raw audio and video streams. Around 2% is a reasonable default for MP4 or MKV; set it to zero if you want the pure elementary-stream arithmetic.
4Switch to target-size mode to invert the calculation: enter the file size you have to fit inside — an upload limit, a disc, a memory card — and the calculator returns the video bitrate that lands on it after reserving room for audio and overhead.
5Two related tools: the [data storage calculator](/calculators/data-storage-calculator) sizes a whole media library once you know what one file costs, and the [bandwidth calculator](/calculators/bandwidth-calculator) turns the same bitrate figure into the connection speed needed to stream it rather than store it.

Related guides

Learn more about this calculation

Guide