The short answer
Drop your audio or video files on the tool below. Keep Mode on Change by decibels and pick a quick button such as +6 dB, or move the slider anywhere from -30 to +30 dB. Each file is processed right away; download it on its own or press Download as ZIP when you have several.
If you want several files to sound equally loud, switch to Normalize and choose a Target level, for example -14 LUFS (YouTube, Spotify). Everything happens on your device, so nothing is uploaded.
Try it here: Volume Booster
Open the full tool pageHow many decibels to add
Volume changes are measured in decibels (dB). Every +6 dB doubles the amplitude of the sound wave, and +10 dB is perceived as roughly twice as loud. The slider shows the same change as a percentage, so you can see that +6 dB means about 200%. Small steps go a long way: +3 dB is a noticeable lift, +6 dB fixes most quiet phone recordings, and +10 to +15 dB is for very faint audio.
Negative values work the same way in the other direction, which is useful when one file in a set is much louder than the rest.
| Change | Amplitude factor | Shown as | How it sounds |
|---|---|---|---|
| -6 dB | 0.50 | 50% | Clearly quieter |
| +3 dB | 1.41 | 141% | A little louder |
| +6 dB | 2.00 | 200% | Clearly louder |
| +10 dB | 3.16 | 316% | About twice as loud |
| +20 dB | 10.0 | 1,000% | Much louder, for very faint recordings |
| +30 dB | 31.6 | 3,162% | The maximum, only for near silent files |
Why boosted audio crackles, and how this avoids it
Digital audio has a ceiling. When a boost pushes a peak past it, a simple amplifier cuts the wave flat, and that hard clipping is heard as crackling or distortion. Many quick volume apps do exactly this.
This tool lets everything below -1 dBFS pass unchanged and bends louder peaks along a smooth curve that approaches the ceiling but never crosses it. Quiet and normal passages get the full boost, and loud moments stay clean. With very large boosts on a file that is already loud, the peaks get squashed and the sound can feel flat or compressed, so add only what you need.
Normalizing: peak or LUFS
Normalize measures each file first and then applies exactly the gain needed. Peak at -1 dB raises the loudest single moment to -1 dB, which is as loud as the file can get without limiting. It is simple, but one short bang decides the result, so two normalized files can still sound very different.
The LUFS targets measure how loud the whole file sounds to the ear. The tool uses the ITU-R BS.1770 method with K-weighting and gating, the same approach broadcasters and streaming services use; in our test a 1 kHz stereo tone at -26 dBFS measured exactly -26 LUFS. It is a close measurement, not a certified meter. The result line shows the measured value and the change, for example From -20.3 to -14 LUFS (+6.3 dB). If reaching the target would push peaks above -1 dB, they are limited softly, so very dynamic files can end slightly below the target.
| Target level | Typical use |
|---|---|
| Peak at -1 dB | As loud as possible without limiting, single files |
| -14 LUFS | Music and video for YouTube, Spotify and similar services |
| -16 LUFS | Podcasts, audiobooks, speech |
| -23 LUFS | Broadcast, the European EBU R128 standard |
Videos and file formats
For MP4, MOV, WebM and MKV videos only the sound is changed: the picture is copied as it is, without re-encoding, so the image quality stays identical and even long videos finish quickly. The sound itself is encoded again at a high bit rate.
Each file keeps its format. MP4, MOV and M4A get AAC sound, WebM, MKV and OGG get Opus, MP3 files are encoded with LAME, and WAV stays uncompressed PCM. FLAC is saved as WAV, which is also lossless, because browsers cannot write FLAC. Firefox cannot create AAC sound, so for MP4, MOV and M4A use Chrome, Edge or Safari.
- MP3 in, MP3 out
- M4A, MP4, MOV: AAC sound, picture copied
- WebM, MKV, OGG: Opus sound, picture copied
- WAV in, WAV out
- FLAC in, WAV out
Other ways to make audio louder
Playback settings, such as a player's volume above 100%, only change what you hear on that device; the file itself stays quiet when you send it on. Video editors such as iMovie and Clipchamp can raise a clip's volume, and the free desktop program Audacity has Amplify and Normalize effects if you want to edit the waveform by hand.
The browser tool is quicker when you only need a louder file, want a whole batch at the same loudness, or are on a computer where you cannot install software.
Common problems and fixes
- The speech is louder but so is the hiss: a volume change raises everything by the same amount, including background noise and hum. It cannot separate a voice from noise.
- The result sounds flat or squashed: the boost was too large for an already loud file. Use a smaller value or Normalize with -14 LUFS.
- Nothing changed after Peak at -1 dB: the file already had a peak close to -1 dB. Use a LUFS target instead, which looks at average loudness.
- This file is silent, so there is nothing to adjust: the file has no audible sound to measure.
- Your browser cannot create this format: Firefox cannot write AAC. Open the tool in Chrome, Edge or Safari for MP4, MOV and M4A.
- The FLAC file came back as WAV: browsers cannot write FLAC, so the lossless WAV format is used instead.