How to Reduce Audio File Size Without Ruining the Sound

Why audio files get big

File size is simply bitrate × duration. A stereo WAV at CD quality uses about 1,411 kilobits for every second, roughly 10 MB per minute. A one-hour interview recorded as WAV is around 600 MB. Even as a 320 kbps MP3, it's still about 144 MB. Shrinking it means lowering the bitrate, shortening the duration, or both.

Technique 1: Convert to a compressed format

If your file is WAV, AIFF or FLAC, converting to MP3 is by far the biggest win. A 192 kbps MP3 is about 86% smaller than a 16-bit WAV, and most people can't hear the difference. Use WAV to MP3 for batches of files.

Technique 2: Lower the bitrate

For an MP3 that's still too large, re-encode it at a lower bitrate. Size scales directly with bitrate, so going from 320 to 128 kbps cuts the file by 60%. How low you can go depends on the content:

Technique 3: Switch to mono

Speech recordings rarely benefit from stereo. Merging left and right into a single channel means the encoder can spend its whole bitrate on one channel, so a 64 kbps mono file usually sounds better than a 64 kbps stereo one.

Technique 4: Lower the sample rate

Voices contain little useful information above about 8–10 kHz. Dropping from 44.1 kHz to 22 kHz or 16 kHz removes those unused frequencies and helps very low bitrates sound cleaner. Avoid this for music, which would sound dull. For the reasoning behind this, see our guide to bitrate, sample rate and bit depth.

Technique 5: Cut what you don't need

Silence costs exactly as much space as sound. Remove dead air at the start and end with the Audio Trimmer, and cut long pauses, false starts or off-topic sections with the Audio Cutter. A 10% shorter file is a 10% smaller file, with zero quality loss.

Putting it together: real examples

The Audio Compressor combines all of these settings in one place and shows the estimated size before you start.

Know the limits you're aiming for

Attachment limits change over time, so check your service's current rules. As a rough guide, popular email services cap attachments at around 20–25 MB and offer a cloud-storage link for anything larger. Messaging apps usually compress audio sent as a voice message but keep files sent as a document intact. If quality matters, send the file as a document.

What not to do

• Don't zip audio files expecting big savings. MP3 and AAC are already compressed, so ZIP barely shrinks them.
• Don't compress the same file repeatedly. Go back to the original and encode once at the settings you need.
• Don't use music settings for speech, or speech settings for music.

Frequently asked questions