27 tools Converters
Video and audio formats, and units with exact conversion factors.
Your files stay on your device. The tool works directly in your browser, using your device to process your files. Nothing is sent to our servers, and we never receive, store, or see your files or figures.
Video
Category page →MOV, MKV, AVI and WebM into MP4, converted on your own machine.
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Video converter
Convert MOV, MKV, AVI, WebM and MP4 in any direction, with the whole conversion running inside your browser.
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MOV to MP4
Turn iPhone and QuickTime MOV files into MP4, usually without re-encoding a single frame.
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MKV to MP4
Convert Matroska MKV files to MP4 in seconds, copying the video across rather than re-encoding it.
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AVI to MP4
Bring old AVI footage from camcorders and 2000s-era files into MP4 that modern devices will actually play.
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WebM to MP4
Convert WebM recordings and downloads to MP4 so phones, editors and social platforms will accept them.
Audio
Category page →MP3, M4A and WAV in every direction, with the bitrate under your control.
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Audio converter
Convert between MP3, M4A, WAV, AAC, OGG and FLAC in batches, with the bitrate under your control.
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MP3 converter
Turn any audio or video file into MP3, at a bitrate you choose, without uploading it anywhere.
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M4A to MP3
Convert iPhone voice memos, iTunes tracks and other M4A files to MP3 that anything will play.
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WAV to MP3
Compress large WAV recordings into MP3 at a bitrate you choose, without uploading anything.
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MP3 to WAV
Decode MP3 files to uncompressed 16-bit WAV for editing, transcription and software that refuses compressed audio.
Video to audio
Category page →Lift the soundtrack out of a video and keep it as MP3.
Units
Category page →Length, weight, temperature, data and speed with exact factors.
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cm to inches
Convert centimetres to inches and back using the exact international factor, with a reference chart and the formula shown.
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kg to lbs
Convert kilograms to pounds and back with the exact international factor, plus a reference chart and stone conversions.
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Celsius to Fahrenheit
Convert °C to °F and back with the formula shown, plus a reference chart of everyday and body temperatures.
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Feet to metres
Convert feet to metres and back with the exact international factor, plus a chart covering heights, room sizes and altitudes.
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Miles to km
Convert miles to kilometres and back with the exact factor, plus speed limits, running distances and a reference chart.
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MB to GB
Convert megabytes to gigabytes in both the decimal (1000) and binary (1024) conventions, and see why your drive looks smaller than the box said.
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mph to km/h
Convert mph to km/h with the exact factor, plus a speed-limit chart for driving abroad and the mental arithmetic that gets you close.
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sq ft to sq m
Convert square feet to square metres with the exact factor, plus why area conversion squares the length factor and a chart of common property sizes.
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Gallons to litres
Convert US and imperial gallons to litres with exact factors, and see why the two gallons differ by twenty per cent.
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Inches to cm
Convert inches to centimetres with the exact factor of 2.54, plus screen sizes, paper sizes and a full reference chart.
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lbs to kg
Convert pounds to kilograms with the exact factor, plus body weight, luggage allowance and gym plate references.
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Fahrenheit to Celsius
Convert °F to °C with the formula shown, plus oven temperatures, body temperature and a weather reference chart.
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KB to MB
Convert kilobytes to megabytes in both the decimal and binary conventions, with a reference chart of common file sizes.
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Cups to ml
Convert cups to millilitres, with the three different cups explained and a note on why baking should be weighed instead.
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Knots to km/h
Convert knots to km/h and mph with the exact factor, plus a Beaufort wind scale reference and why aviation still uses them.
Four different jobs under one word
"Convert" covers two things that have almost nothing in common. Turning kilograms into pounds is arithmetic with an exact factor; turning an MKV into an MP4 is rewriting a media container around a video stream. They share a verb and a page on this site, and that is all, which is why the tools above are split into video, audio, video to audio and units.
Media conversion runs on your machine, not ours
Every other free video and audio converter uploads your file, converts it on a server, and hands you a download link. The tools here run a full copy of FFmpeg, compiled to WebAssembly, inside your browser tab. It is a 9.8 MB download the first time you convert something and it is kept afterwards, so nothing is uploaded, there is no queue, and there is no size limit beyond what your own machine can hold.
Most format changes turn out not to need re-encoding at all. A MOV from an iPhone and an MP4 from an Android phone usually contain the same H.264 video and the same AAC audio inside different wrappers, so the conversion copies both streams across untouched: seconds rather than minutes, and mathematically identical to the original.
Unit conversion uses exact factors
Every metric-to-imperial factor comes from the 1959 International Yard and Pound Agreement: an inch is exactly 2.54 cm, a pound is exactly 0.45359237 kg, a mile is exactly 1,609.344 m. These are definitions rather than measurements, and each converter shows the factor it used so the arithmetic can be checked. Temperature is the exception, because its scales have different zero points and need an offset as well as a ratio.
