Audio File Size Calculator: Formula & Examples

This calculator works out the file size of an uncompressed digital audio recording. You enter the audio duration, sample rate, bit depth, and number of channels, and it returns the file size in megabytes, kilobytes, and bits. The result helps you plan storage or estimate download times before you record or convert audio.

Formula

The file size of uncompressed PCM audio (like a WAV or AIFF file) is calculated with this formula:

File Size (bytes) = Duration (seconds) × Sample Rate (Hz) × Bit Depth (bits) × Number of Channels ÷ 8

Where:

• Duration – length of the audio in seconds (or minutes × 60).
• Sample Rate – number of samples taken per second, in Hz (e.g., 44,100 Hz for CD quality).
• Bit Depth – number of bits used to store each sample (e.g., 16 bits for CD, 24 bits for studio).
• Number of Channels – 1 for mono, 2 for stereo, 6 for 5.1 surround.
• ÷ 8 – converts bits to bytes.

The result is in bytes. To get kilobytes, divide by 1024; to get megabytes, divide by 1024 again (or by 1,048,576 directly).

Worked Example

Using the default values from the calculator: 3 minutes, 44,100 Hz, 16-bit, stereo (2 channels).

1. Convert duration to seconds: 3 × 60 = 180 seconds.
2. Multiply by sample rate: 180 × 44,100 = 7,938,000 samples per channel.
3. Multiply by bit depth: 7,938,000 × 16 = 127,008,000 bits per channel.
4. Multiply by channels: 127,008,000 × 2 = 254,016,000 bits total.
5. Convert to bytes: 254,016,000 ÷ 8 = 31,752,000 bytes.
6. Convert to megabytes: 31,752,000 ÷ 1,048,576 ≈ 30.28 MB.

The calculator shows 30.28 MB, matching this manual calculation.

Why File Size Matters

Knowing the file size of uncompressed audio is useful for several real-world situations:

• Storage planning: If you record a podcast or interview, you need to know how much space the raw files will take on your hard drive or SD card.
• Upload/download estimates: A 30 MB file takes about 30 seconds to upload on a 10 Mbps connection (roughly, because of overhead).
• Comparing formats: Uncompressed WAV files are huge compared to MP3 or AAC. This calculator shows why – a typical MP3 at 128 kbps for 3 minutes is only about 2.8 MB, while the same audio as WAV is 30 MB.
• Setting recording equipment: If you know your recorder’s available space, you can calculate how long you can record before running out.

How to Choose the Right Settings

Your choice of sample rate and bit depth depends on the purpose of the audio:

• Voice/memo (telephone quality): 8,000 Hz, 8-bit, mono – very small files, but poor fidelity. Useful for speech recognition or dictation.
• Podcast/voice recording: 44,100 Hz, 16-bit, mono or stereo – standard for speech, gives good quality with reasonable size.
• Music CD: 44,100 Hz, 16-bit, stereo – this is the CD standard.
• Professional music production: 48,000 Hz or 96,000 Hz, 24-bit – higher sample rates and bit depth preserve detail, but files become much larger.
• Film/video: 48,000 Hz, 24-bit – the standard for video production.

If you are unsure, 44.1 kHz / 16-bit / stereo is a safe default for most music and general audio.

Common Mistakes and Misconceptions

People often make these errors when estimating audio file sizes:

• Forgetting to divide by 8: The formula gives bits, not bytes. A 3-minute CD-quality song is about 254 million bits, which sounds huge until you divide by 8 to get 31.75 million bytes (30 MB).
• Using 1000 instead of 1024: Hard drive manufacturers use decimal (1 MB = 1,000,000 bytes), while operating systems often use binary (1 MB = 1,048,576 bytes). This calculator uses binary, so the result might be slightly smaller than what your file manager shows if it uses decimal.
• Confusing sample rate with bit rate: Sample rate is how many samples per second; bit rate is how many bits per second. For uncompressed audio, bit rate = sample rate × bit depth × channels. For compressed audio, bit rate is a separate setting (e.g., 128 kbps MP3).
• Assuming all audio is uncompressed: This formula applies to WAV, AIFF, and other PCM formats. Compressed formats like MP3, AAC, or FLAC use different algorithms and result in much smaller files.

Limits of the Formula

This formula calculates the raw audio data size only. The actual file on disk will be slightly larger because of the file header (typically 44 bytes for WAV, 12 bytes for AIFF) and any metadata tags (title, artist, etc.). For most practical purposes, that extra overhead is negligible (less than 1 KB).

The formula also assumes uncompressed PCM audio. If you are working with compressed formats, you need a different approach – usually based on bit rate and duration. For example, an MP3 at 128 kbps for 3 minutes is approximately 128,000 bits per second × 180 seconds ÷ 8 = 2.88 MB.

Frequently Asked Questions

How many MB is one hour of CD-quality audio?

One hour of 44.1 kHz, 16-bit, stereo audio is 60 minutes × 60 seconds × 44,100 × 16 × 2 ÷ 8 ÷ 1,048,576 ≈ 605 MB. That is roughly 0.6 GB per hour. For 24-bit/96 kHz stereo, it jumps to about 1.65 GB per hour.

Why is a 3-minute WAV file 30 MB but an MP3 of the same song is only 3 MB?

MP3 uses lossy compression that discards audio data the human ear is less likely to notice. It also uses a constant bit rate (e.g., 128 kbps) that is much lower than the raw bit rate of CD audio (1,411 kbps). The trade-off is lower file size at the cost of some audio fidelity.

Does bit depth really matter for file size?

Yes, directly. Doubling the bit depth (from 16 to 32 bits) doubles the file size. Bit depth affects dynamic range – the difference between the quietest and loudest sounds. 16-bit gives about 96 dB of dynamic range, while 24-bit gives about 144 dB, which is why studio recordings use 24-bit even if the final product is 16-bit.

What is the difference between sample rate and bit rate?

Sample rate is how often the audio signal is measured per second (e.g., 44,100 times per second). Bit rate is how many bits are used per second of audio. For uncompressed audio, bit rate = sample rate × bit depth × channels. For compressed audio, bit rate is a separate setting that determines quality and file size.

Can I use this calculator for compressed audio files?

No, this calculator is only for uncompressed PCM audio. For compressed formats, you need to know the bit rate (e.g., 128 kbps for MP3) and duration. The formula is: file size (bytes) = bit rate (bits per second) × duration (seconds) ÷ 8. For example, a 3-minute MP3 at 128 kbps is 128,000 × 180 ÷ 8 = 2,880,000 bytes ≈ 2.75 MB.

Why does my file manager show a different size than this calculator?

There are two reasons. First, the file header and metadata add a few hundred bytes. Second, some operating systems display sizes in decimal (1 MB = 1,000,000 bytes) while others use binary (1 MB = 1,048,576 bytes). This calculator uses binary, so your file manager might show a slightly larger number if it uses decimal.

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in dur | Duration | minutes | 3 | 0
in sr | Sample rate | Hz | 44100 | 8000
in bd | Bit depth | bits | 16 | 8
in ch | Channels | - | 2 | 1
out mb | File size | MB | (dur * 60 * sr * bd * ch) / 8 / 1048576 | 2
out kb | File size | KB | (dur * 60 * sr * bd * ch) / 8 / 1024 | 1
out bits | Total bits | bits | dur * 60 * sr * bd * ch | 0