Audio File Size Calculator
Estimate audio file size from bitrate.
MP3 ~128-320, podcast ~64-96
Results update as you type.
How it works
Audio file size depends mainly on the bitrate and length, and this calculator estimates it. You enter the duration in minutes and the bitrate in kilobits per second (kbps), and it returns the file size in megabytes and kilobytes. The bitrate is how much data the audio uses each second: multiplying it by the total seconds gives the total kilobits, and dividing by 8 converts to kilobytes since there are 8 bits in a byte. Bitrate is the key quality-versus-size trade-off. Common MP3 bitrates range from 128 kbps (decent quality, small files) up to 320 kbps (near-CD quality, larger files), while spoken-word content like podcasts and audiobooks sounds fine at 64 to 96 kbps, keeping files small. For example, a 4-minute song at 128 kbps is about 3.75 MB, while the same song at 320 kbps is about 9.4 MB. This estimate applies to constant-bitrate compressed audio; variable-bitrate (VBR) files vary around an average, and uncompressed formats like WAV are far larger. Knowing the size helps you plan storage for a music library, keep podcast episodes within hosting limits, or estimate download and streaming data. Enter the duration and bitrate to estimate the audio file size.
Size (KB) = bitrate (kbps) × duration (s) ÷ 8
Bitrate is the data used per second in kilobits, so multiplying it by the duration in seconds gives total kilobits, and dividing by 8 converts to kilobytes. A higher bitrate means better audio quality but a larger file, while a lower bitrate saves space at the cost of fidelity.
Source:Digital audio basics
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter duration.
- 2
Adjust the options
Adjust bitrate if they apply — sensible defaults are already set.
- 3
Read your result
File size updates instantly as you type — no button to press.
Frequently asked questions
How do you calculate audio file size?
Multiply the bitrate in kilobits per second by the duration in seconds, then divide by 8 to convert kilobits to kilobytes. A 4-minute (240-second) track at 128 kbps is 3,840 KB, or about 3.75 MB. Divide by 1024 for megabytes. The calculator does this and shows the size in both KB and MB.
What bitrate should I use for audio?
For music, 128 kbps is acceptable, 192 to 256 kbps is good, and 320 kbps is near-CD quality but larger. For spoken word like podcasts and audiobooks, 64 to 96 kbps sounds clear while keeping files small. Choose based on whether fidelity or file size matters more for your use, since higher bitrate means bigger files.
Why does higher bitrate mean better quality?
Bitrate is how much data represents each second of audio. A higher bitrate preserves more detail, capturing subtle sounds and reducing compression artifacts, so the audio sounds closer to the original. A lower bitrate discards more information to shrink the file, which can make music sound muffled or harsh, though speech tolerates low bitrates well.
What is the difference between CBR and VBR?
Constant bitrate (CBR) uses the same data rate throughout, making size easy to calculate as this tool does. Variable bitrate (VBR) adjusts the rate moment to moment, using more data for complex passages and less for simple ones, which can give better quality per size. VBR file size varies around an average bitrate rather than being exact.
How big are uncompressed audio files?
Uncompressed formats like WAV or AIFF are much larger than MP3. CD-quality WAV runs about 10 MB per minute, roughly ten times a 128 kbps MP3. That is why compressed formats are used for distribution and streaming, while uncompressed audio is reserved for editing and archiving where maximum quality matters and storage is not a concern.