Audio Duration Calculator
Calculate audio playback duration from file size (MB) and bitrate (kbps). Pure math — no FFmpeg, instant result. Useful for planning storage, podcast publishing, and CBR encoding.
For PCM/lossless audio.
Result
Duration (seconds)
180.000 s
Duration (HH:MM:SS)
3m 0s
For PCM (uncompressed) audio: duration = total samples ÷ sample rate. For compressed audio: duration ≈ (file size in bits) ÷ bitrate. CBR files are exact; VBR/ABR files are approximate.
About Audio Duration Calculator
Calculate audio playback duration from file size (MB) and bitrate (kbps). Pure math — no FFmpeg, instant result. Useful for planning storage, podcast publishing, and CBR encoding.
This calculator runs entirely in your browser using plain JavaScript math — no server round-trip and no upload. Inputs and results stay on your device. Closing or refreshing the tab discards everything immediately.
Related tools
About Audio Duration Calculator
Audio Duration Calculator performs audio duration calculator as a focused single-page utility. Calculate audio playback duration from file size (MB) and bitrate (kbps). Pure math — no FFmpeg, instant result. Useful for planning storage, podcast publishing, and CBR encoding. Defaults are tuned for the common case so the first run is one click, with every option that matters exposed for the moments you need to fine-tune the result.
Internally the tool runs on standard browser APIs — the same processing stack used by professional desktop pipelines, just compiled for the browser. MP3, WAV, M4A, AAC, OGG, Opus, FLAC, AIFF, and WMA files are accepted natively. 200 MB is the practical ceiling, set so the tool stays responsive on phones and older laptops.
Reach for Audio Duration Calculator when you need a predictable result on a single file. The page works on the first visit, the controls are visible without a menu, and the output is delivered the moment the engine finishes.
The architecture is local-first by design. Once the page is loaded, you can disconnect from the network and the tool still completes the job. The processing stack — standard browser APIs and the small UI shell wrapping it — ships with the page itself, so the tool keeps working in offline conditions, on a captive-portal Wi-Fi, or behind a corporate proxy that limits what the tab can reach.
A practical note on limits: Audio Duration Calculator accepts inputs up to 200 MB per run, and the tool processes one input at a time to keep memory usage predictable. If you ever bump into the ceiling, the cause is the size of the input.
Audio Duration Calculator fits naturally next to several adjacent tools. Common companions include Audio Bitrate Calculator, Audio File Size Calculator, Audio File Size Estimator, and Audio Metadata Viewer — combine them when the job needs more than one transformation. After running Audio Duration Calculator, many users move on to Audio Bitrate Calculator and Audio File Size Calculator. Each tool is a separate page so you can compose the exact pipeline you need.
Audio Duration Calculator sees the most use from sound designers prototyping cues and voice-over artists exporting takes, 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.
Once the engine finishes, `{name}-edited.{ext}` is offered as an immediate download. There is no preview gate, no email-wall, and no "register to download" intermediary — the file is yours the moment it is ready.
Audio Duration Calculator keeps the control set focused. Every option on the page is there because a real workflow needs it, and the defaults aim at the most common case so a first-time user can get the right output without changing any settings.
From a product perspective, Audio Duration Calculator is one of the simplest possible expressions of "do one thing well." The catalog contains dozens of related tools that each handle a slightly different audio editing and conversion task, and every one is a separate page rather than a tab inside a larger app. That separation keeps each tool fast to load and easy to bookmark.
Tips from users who reach for Audio Duration Calculator regularly: process one input first to confirm the settings produce what you expect before committing to a batch; treat the page as the working surface and avoid leaving large jobs running in a backgrounded tab where the browser may throttle JavaScript; and if a particular file fails, check whether the source is intact by opening it in its native viewer — most "tool errors" are actually input errors.
Audio Duration 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 audio editing and conversion workflow.
When something goes wrong, the cause is usually one of three things: a malformed input, a browser that is out of memory, or a corporate proxy that is interfering with the page's static assets. The first two are easy to diagnose; the third typically requires asking your IT team to allow standard browser APIs to load.
That is the whole tool. Use Audio Duration 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 Audio Duration Calculator in your browser. The page loads quickly and the tool is ready to use the moment it becomes interactive.
- 2Select the MP3, WAV, M4A, AAC, OGG, Opus, FLAC, AIFF, and WMA file you want to process — drag-and-drop and the file picker both work.
- 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 (standard browser APIs) processes the input in the page; you can watch the progress indicator until it completes.
- 5Save the output (`{name}-edited.{ext}`) when it is ready.
- 6Run additional jobs as needed. The same controls and defaults apply on every run.
Common use cases
- Convert a band's rough mix into a format mastering software accepts using Audio Duration Calculator.
- Boost a quiet interview recording to a normal listening level.
- Record a quick test tone to verify a microphone setup.
- Trim the cough out of the first ten seconds of a podcast take.
- Stitch several voice notes into a single playable file.
- Convert a voice memo into a format your editor can open.
- Compress a music demo small enough to share over messaging.
- Re-encode a lossless track into a portable format for the gym.
FAQ
How does the calculator work?
Pure JavaScript math. The formula is: duration in seconds = (file size in MB × 8 × 1024) ÷ bitrate in kbps. The result is shown in seconds, minutes, and HH:MM:SS format. No file is needed and no FFmpeg loads — it's instant.
When is this useful?
Estimating how long a podcast file will play if you only know its size, predicting the duration of a recording you haven't made yet, planning streaming/storage budgets, or sanity-checking metadata that looks wrong. It also helps when receiving raw audio without metadata where the player can't determine duration.
Will the result match my actual file?
For CBR (constant bitrate) audio, the result is essentially exact (within 1%). For VBR (variable bitrate) audio common in modern MP3s, the calculated duration is the average — actual files may vary by ±5% because VBR uses different bitrates for different sections.
Why is this not slower in the browser?
Unlike audio transcoding, this is pure arithmetic — there's no FFmpeg WebAssembly involved. Results are instant and identical to any server-side tool. The "in-browser is slower" caveat only applies to actual audio processing.
What units do I use?
File size in megabytes (MB). Bitrate in kilobits per second (kbps) — the standard MP3 / AAC encoding setting. So a 5 MB file at 128 kbps gives: (5 × 8 × 1024) ÷ 128 = 320 seconds = 5:20.
How is this different from "Audio Bitrate Calculator"?
This calculator goes from size + bitrate → duration. The Bitrate Calculator goes from size + duration → bitrate. The File Size Calculator goes from duration + bitrate → size. Together they cover all three relationships between the variables.
Why is in-browser audio processing slower than online tools?
Server-side tools use multi-threaded native FFmpeg running on dedicated CPUs with fast disks and parallel pipelines. Our engine is FFmpeg compiled to WebAssembly, which runs single-threaded inside your browser tab and has no access to native hardware acceleration. That makes browser-based jobs typically 3–8× slower than a server. The trade-off is total privacy: your audio file is never uploaded, never logged, and never stored — closing the tab erases everything from memory immediately. For most clips up to a few minutes the wait is small, and for sensitive recordings (voice memos, drafts, confidential meetings) the privacy gain is well worth it.
Is my audio uploaded?
No. Everything runs entirely inside your browser tab using FFmpeg compiled to WebAssembly. The file is read into local memory only, processed in the same tab, and the result is offered as a direct download. Nothing is transmitted to any server, no account is required, no analytics are tied to your file, and closing the tab discards every byte from memory.
How big a file can I process?
The file picker accepts audio inputs up to about 1 GB, which is well above what mainstream "free tier" online converters allow. The real ceiling is your device — everything runs inside your browser tab, which shares memory with the rest of the page. Most podcasts, songs, and voice memos sit comfortably under that limit even on a phone. If a very large lossless WAV or FLAC ever fails, trim it first or transcode to MP3 / Opus to bring the size down before re-running the tool.
Which audio formats are supported?
MP3, WAV, OGG (Vorbis and Opus), FLAC, M4A (AAC), AAC, Opus, AIFF, and WMA all decode reliably via FFmpeg WASM. Output formats depend on the specific tool — most editing tools default to MP3 (universal) or WAV (lossless) but expose a format picker so you can pick the one that fits your downstream player or DAW.
Which browsers are supported?
Recent Chrome, Edge, Firefox, Safari, and other Chromium-based browsers all work. The tool relies on WebAssembly and SharedArrayBuffer, which require the page to be served over HTTPS with the right cross-origin headers — this site is configured correctly by default. On phones the same code runs but is slower than on a desktop because mobile CPUs are weaker.
Is there a watermark, sign-up wall, or usage cap?
No. The tool is completely free, requires no account, attaches no watermark, applies no usage caps, and shows no popup ads on your output. Because the work happens on your own device, there is no per-user quota for us to enforce — your hardware and browser memory are the only limits. The download is the file you would get from running FFmpeg locally, nothing more, nothing less.
Why use Audio Duration 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. Audio Duration Calculator sits in between: free, instant, and private, but intentionally narrow in scope. For one-off jobs and the common audio editing and conversion operations, it is usually the lowest-friction choice; for highly specialised work, a dedicated app is still the right answer.
Is Audio Duration Calculator mobile-friendly?
Audio Duration Calculator runs in any modern mobile browser — Safari, Chrome, Firefox and the in-app browsers in most messaging apps all support the underlying APIs. Performance depends on the device: a recent phone handles typical inputs nearly as fast as a laptop, while older devices may take a few seconds longer near the 200 MB ceiling. The interface lays out cleanly on small screens, so you do not need to pinch-zoom to see the controls.
Can I use Audio Duration Calculator for commercial work?
Audio Duration Calculator can be used for personal and commercial work alike — there is no separate "business" licence to purchase. The output you generate is yours to use however you want, including in client deliverables, internal documents, or commercial products. Favtoo's only ask is fair, individual use; the tool is not designed to be embedded as a backend service or wrapped behind an API for resale.
Can I self-host Audio Duration Calculator for my team?
Audio Duration Calculator is a static page running an open-source engine in your browser, so a typical corporate firewall does not get in the way as long as it allows JavaScript to load from Favtoo. For teams that need to host it themselves on an internal network, the underlying engine (standard browser APIs) is open-source and can be packaged into a private build with the same behaviour. Reach out via the Contact page if that is something you are exploring.
Are jobs run with Audio Duration Calculator stored anywhere?
Favtoo keeps no copy of your file because Favtoo never receives your file. Audio Duration 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.
Do I need a specific browser to use Audio Duration Calculator?
Audio Duration 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.
What should I do if Audio Duration 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 MP3, WAV, M4A, AAC, OGG, Opus, FLAC, AIFF, and WMA and that it is below 200 MB. For the third, opening the file in its native viewer first is the fastest way to confirm the source is intact.
Why is my browser prompting me when I open Audio Duration Calculator?
Audio Duration Calculator only needs the standard web platform — file picker access for the inputs you choose to load, and optionally clipboard access if you copy the result rather than downloading it. There is no microphone, camera, geolocation or background-permission request, because none of those are needed for the work the tool does.