Video Bitrate Calculator
Calculate the exact video bitrate (kbps) you need to hit a target file size. Enter the size in MB, the duration in seconds, and your audio bitrate — get the exact video bitrate to plug into your encoder. Pure math, runs instantly in your browser.
How big you want the final file to be.
Total video length in seconds.
Required bitrate
- Video bitrate
- 1,237 kbpsUse this with `-b:v`
- Audio bitrate
- 128 kbps
- Total bitrate
- 1,365 kbps
- Video bitrate (Mbps)
- 1.237 Mbps
- Total file size check
- 100 MB
About Video Bitrate Calculator
Video Bitrate Calculator is a video tool that runs in your browser. Calculate the exact video bitrate (kbps) you need to hit a target file size. Enter the size in MB, the duration in seconds, and your audio bitrate — get the exact video bitrate to plug into your encoder. Pure math, runs instantly in your browser. The page you are reading is the same workspace you will use to do the work: pick a file or paste your input, choose the options that matter to you, and the tool produces the result on your device.
Video Bitrate Calculator sees the most use from event organisers sharing highlight footage and teams compressing demo recordings, but the design is intentionally generic enough that you do not need a specialist background to get a good result. The defaults aim at the most common case so a first-time user can get the right output without changing any settings.
Video Bitrate Calculator is shaped for the gap between "I'll do it by hand" and "I'll script it." When the job is small enough that automating it would take longer than doing it, but annoying enough to want a focused tool — that is the situation this page is built for.
Video Bitrate Calculator runs on FFmpeg compiled to WebAssembly — an open-source, well-audited engine that performs the video editing and conversion natively in the browser. It accepts MP4, WebM, MOV, MKV, AVI, FLV, and OGV and produces output that opens in any standard video viewer. Per-run input is capped at 500 MB.
Because everything runs in the page, the tool scales the same way for one user or a million — there is no per-user backend cost. The page is static, the engine is the same JavaScript bundle for every visitor, and the work happens on the visitor's own device. That keeps the tool free and keeps it fast on the first interaction.
If your task needs more than one step, chain Video Bitrate Calculator with Video File Size Calculator, Video Duration Calculator, and Video Bitrate Reducer. Each tool produces output that is a clean input to the next, so multi-step workflows are just a matter of opening the next tool in a new tab and continuing.
The only practical limit is the 500 MB per-file ceiling, which keeps the tool responsive across a wide range of devices. Run the tool ten times in a row, run it ten thousand times — it behaves the same way and produces the same quality of result.
The transformation in Video Bitrate Calculator is deterministic — the same input plus the same options produces the same result every run. That predictability matters when the result has to match an upstream specification or be reproducible later.
Output handling is intentionally boring: Video Bitrate Calculator produces `{name}-edited.{ext}` and triggers your browser's standard "save" behaviour. If you have a default download folder configured, that is where it will land. There is no Favtoo-side history of jobs you have run.
Video Bitrate Calculator is one example of a broader pattern: utility software increasingly works as single-page, client-side experiences. Every page in the catalog is shaped that way, which keeps each tool fast to load and easy to recommend in a single link.
Video Bitrate Calculator is built around the moment of need: a focused page you open when you have a specific task, complete the task, and close. The catalog contains many adjacent tools so the same model serves the surrounding parts of a typical video editing and conversion workflow.
Useful patterns when working with Video Bitrate Calculator: keep the input file open in another tab so you can compare against the result; give the output file a descriptive name when saving so you can find it later (the default name is sensible but generic); and treat each run as independent — the tool has no concept of "history", which means you cannot accidentally pollute one job with leftovers from another.
Common gotchas worth flagging: Video Bitrate Calculator only accepts MP4, WebM, MOV, MKV, AVI, FLV, and OGV, so if your file is in another format you will need to convert it first. The 500 MB ceiling is per-file, not per-session; you can run as many separate jobs as you like, but a single oversized input will be rejected on load.
That is the whole tool. Use Video Bitrate Calculator for as long as it stays useful to you, and if it does, the catalog has many more tools built the same way. Each applies the same single-purpose discipline, so the way you used this page transfers to the next one you try.
How it works
- 1Open Video Bitrate Calculator in your browser. The page loads quickly and the tool is ready to use the moment it becomes interactive.
- 2Drop a MP4, WebM, MOV, MKV, AVI, FLV, and OGV file onto the upload area, or click to pick one from your device.
- 3Tweak the controls if the defaults are not quite right for your input. The options are kept short and labelled in plain language.
- 4Click to start the job. The engine (FFmpeg compiled to WebAssembly) processes the input in the page; you can watch the progress indicator until it completes.
- 5Grab the output named `{name}-edited.{ext}` as soon as the run completes. You can also copy the result instead of downloading if the next tool in your workflow accepts pasted input.
- 6Run additional jobs as needed. The same controls and defaults apply on every run.
Common use cases
- Re-encode a clip so it plays on an older device without stuttering using Video Bitrate Calculator.
- Rotate a portrait phone clip into landscape for embedding on a site.
- Convert a phone-recorded clip into a web-friendly MP4.
- Cut a long meeting recording down to the relevant five minutes.
- Add a quick caption overlay before posting to social.
- Compress a demo video small enough to attach to an email.
- Trim the silent intro from a screen recording before sharing it.
- Convert a desktop recording into a GIF for documentation.
Frequently asked questions
How does the calculator work?
Pure JavaScript math: total bitrate (kbps) = (file size MB × 8 × 1024) / duration in seconds. Subtract the audio bitrate to get the required video bitrate. Plug that number directly into FFmpeg with `-b:v`.
Why use this tool?
Most encoders ask for a target bitrate, but you usually know the target file size instead. Use this to convert between the two — for example to fit a video under Discord's 25MB limit, an email attachment cap, or a streaming platform's ceiling.
Why is this not slower in browser?
Unlike video transcoding, this is pure arithmetic — there is no FFmpeg WebAssembly involved. Results are instant and identical to any server-side tool.
Which audio bitrate should I pick?
128 kbps is the standard for stereo music and dialogue. 64 kbps for mono podcasts. 192–320 kbps for high-fidelity music. Lower audio bitrate means more headroom for video quality at the same total file size.
Are results guaranteed?
For two-pass encoding the result is highly accurate (within 1–2%). For one-pass CRF encoding actual file size varies with scene complexity. Use the Video Size Estimator for content-aware estimates.
How do I use the result with FFmpeg?
Use the video kbps value with `-b:v <value>k` (e.g. `-b:v 1500k`). For best results add `-maxrate <1.5×value>k` and `-bufsize <2×value>k` to enforce the target.
Why is the video bitrate 0 or negative?
Your audio bitrate is higher than the total bitrate the file size + duration allows. Either reduce audio bitrate or increase the target file size.
Is anything logged?
No. The calculator runs entirely in your browser tab. Nothing is transmitted, stored, or logged.
How many times per day can I use Video Bitrate Calculator?
Inputs are capped at 500 MB per file, which keeps memory usage stable across phones, tablets and older laptops. You can run Video Bitrate Calculator as often as you need; every run produces a full-quality result.
What should I do if Video Bitrate Calculator fails on my file?
Failures usually fall into one of three buckets: the input is in an unsupported format, the input is over the size cap, or the input is structurally malformed (a truncated download, a partial export, or a stream the engine does not recognise). The first two are easy to confirm — check that your file is one of MP4, WebM, MOV, MKV, AVI, FLV, and OGV and that it is below 500 MB. For the third, opening the file in its native viewer first is the fastest way to confirm the source is intact.
How do I run Video Bitrate Calculator over a folder of files?
Video Bitrate Calculator processes one input at a time by design — it keeps memory usage predictable on lower-end devices and makes results easier to verify. To handle a folder, run the tool once per file; the page stays loaded between runs and remembers your last-used settings, so the second run is essentially instant.
Will Video Bitrate Calculator ask me to pay to download the result?
Video Bitrate Calculator is free to use. The processing runs in your browser, which keeps the per-user cost low enough that the tool can be offered openly. The download is the same file the engine produced — you can use it for as many runs as you need.
Which file formats does Video Bitrate Calculator accept?
Video Bitrate Calculator accepts MP4, WebM, MOV, MKV, AVI, FLV, and OGV. If your input is in a format that is not directly supported, convert it first using one of Favtoo's converter tools — every Favtoo converter outputs a file that is a clean input to the next tool in the chain.
How long does Favtoo retain my data after using Video Bitrate Calculator?
Favtoo keeps no copy of your file because Favtoo never receives your file. Video Bitrate Calculator runs entirely in your browser, the input is held only in your tab's memory, and closing the tab discards it. There is no opt-in cloud history, no "recent jobs" panel synced to an account, and no server-side retention to configure — the architecture simply has nowhere for your file to be stored.
Why use Video Bitrate Calculator instead of a paid online tool?
Desktop apps usually have more advanced features but require installation, maintenance and (often) a licence. Paid online tools are convenient but route your file through their servers and gate downloads behind accounts. Video Bitrate Calculator sits in between: free, instant, and private, but intentionally narrow in scope. For one-off jobs and the common video editing and conversion operations, it is usually the lowest-friction choice; for highly specialised work, a dedicated app is still the right answer.
Is Video Bitrate Calculator keyboard accessible?
Video Bitrate Calculator uses native HTML controls wherever possible, which means keyboard navigation, focus rings, and screen-reader labels work the way the platform expects. The drop zone accepts files via the keyboard-accessible file picker as well as drag-and-drop, and result downloads use standard browser download flows. If you spot an accessibility gap, Favtoo treats it as a bug worth fixing.
Do I need a specific browser to use Video Bitrate Calculator?
Video Bitrate Calculator works in any modern browser released in the last few years — Chrome, Edge, Firefox, Safari, Brave, Arc and the major Chromium derivatives are all supported. The underlying engine relies on widely-supported web APIs, so there is nothing exotic to install. If you are on a very old browser version and the tool fails to load, updating to the latest release of your preferred browser is the only fix needed.