---
title: "Audio File Size Calculator: WAV & MP3 | Sound Attic"
description: "WAV or MP3 file size from sample rate, bit depth, channels and length, or from a bitrate, and how many hours of recording fit on a drive or card."
url: https://soundattic.me/audio-file-size-calculator/
---

WAV · MP3 · MB and MiB

# Audio file size calculator

How big a recording will be, and how many hours fit on your card or drive, worked out the way the bytes add up.

## How the bytes add up

Uncompressed audio stores one number per channel for every sample, so its size is simple multiplication:

bytes = sample rate × bit depth ÷ 8 × channels × seconds

An hour of 48 kHz, 24-bit stereo is 48,000 × 3 × 2 × 3,600 = 1,036,800,000 bytes. A WAV file adds a small header, 44 bytes for a basic file or 68 for the extensible format used beyond 16 bits or two channels, and recorders may add metadata chunks. For MP3, AAC and other compressed files, the size is the bitrate times the length; tags and artwork add a little.

**MB or MiB?** Sizes are shown both ways. A megabyte (MB) is 1,000,000 bytes and a mebibyte (MiB) is 1,048,576 bytes, so the same file is about 1,037 MB or 989 MiB. Some systems label the binary figure “MB”, which is why a file can look smaller on one computer than another.

A classic WAV file cannot pass 4 GiB, because its size fields are 32 bits. Long multitrack takes need RF64 or BW64, or a recorder that splits files.

**Grabbing free sample packs or impulse responses?** They are often handed out in exchange for an email address, followed by newsletters. A temporary inbox from [CleanTempMail](https://cleantempmail.com/) receives the download link with no sign-up and empties itself after three days, so download straight away: the inbox and its messages will not be there later. Use your real address for any plugin or software licence you may need to recover or download again.

## Sources

- WAVE file structure: RIFF header, a 16-byte fmt chunk for PCM (40 bytes for WAVE_FORMAT_EXTENSIBLE, which should be used for more than 16 bits or more than two channels) and the data chunk: P. Kabal, [Audio File Format Specifications: WAVE](https://www.mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html), McGill University. The 44 and 68-byte totals add up those parts.
- The 4 GB limit of RIFF/WAVE and BWF from 32-bit addressing, and the RF64 format that lifts it: EBU, [Tech 3306, MBWF / RF64: An extended file format for audio](https://knowledgehub.ebu.ch/files/live/sites/tech/files/shared/tech/tech3306v1_1.pdf), version 1.1 (July 2009), since taken up in Recommendation ITU-R BS.2088 (BW64).
- Decimal and binary prefixes (MB = 10⁶ bytes, MiB = 2²⁰ bytes): NIST, [Prefixes for binary multiples](https://physics.nist.gov/cuu/Units/binary.html).

## Questions

**Is 32-bit float twice the size of 16-bit?**

Yes. Each sample takes 4 bytes instead of 2, so at the same sample rate and channel count a 32-bit float file is twice as big as a 16-bit one, and a third bigger than 24-bit.

**How do I work out a multitrack session?**

Enter the total number of mono tracks as channels. Eight mono microphone tracks at 48 kHz and 24-bit come to about 4.15 GB an hour.

**Why does my card hold less than the calculator says?**

Formatting and the recorder’s own files take some space, and a card may be sold in GB but shown in GiB. Enter the free space your recorder or computer reports, in the unit it uses.