How to Calculate PCM Audio Bitrate

PCM (pulse-code modulation) is uncompressed digital audio. Every second of sound is stored as a fixed number of samples, so its bitrate depends only on three settings: sample rate, bit depth and number of channels. You do not need to run an encoder or measure anything to find it. Multiply the three values and you have the exact data rate of the audio stream.

Before you start

The calculation is plain arithmetic and runs entirely on your side: a calculator or spreadsheet is enough, and no online service or upload is involved. What you do need is the correct format details for the audio you are working with. Collect these values from your recording software, audio interface settings, the input device or output device configuration, or the properties of an existing file:

• Sample rate in hertz, for example 44,100 Hz or 48,000 Hz.
• Bit depth per sample, for example 16-bit or 24-bit.
• Number of channels: 1 for mono, 2 for stereo, more for multichannel audio.
• Duration in seconds, if you also want to estimate file size.

Confirm that the audio really is PCM. Formats such as WAV and AIFF usually contain PCM, but a WAV file can also hold compressed data. MP3, AAC, Opus and FLAC do not follow this formula, because their bitrate is set by the encoder rather than by the sample format.

Step-by-step instructions

Follow these steps in order. Nothing here changes your audio, so you can repeat the calculation with different settings as often as you like.

• Write down the sample rate in samples per second. A setting shown as 48 kHz equals 48,000.
• Write down the bit depth. Use the number of bits per sample as stored in the file, such as 16 or 24.
• Write down the channel count.
• Multiply the three numbers: bitrate in bits per second = sample rate × bit depth × channels.
• Divide by 1,000 to get kilobits per second (kbps), or by 1,000,000 to get megabits per second (Mbps).
• To estimate the size of the audio data, multiply the bitrate by the duration in seconds and divide by 8 to convert bits to bytes.

Example for CD-quality audio: 44,100 × 16 × 2 = 1,411,200 bits per second, which is 1,411.2 kbps. One minute of this audio contains 1,411,200 × 60 ÷ 8 = 10,584,000 bytes, about 10.6 MB.

Example for a common video and production format: 48,000 × 24 × 2 = 2,304,000 bits per second, or 2,304 kbps. One minute is 2,304,000 × 60 ÷ 8 = 17,280,000 bytes, about 17.3 MB.

Example for a mono voice recording: 48,000 × 16 × 1 = 768,000 bits per second, or 768 kbps. Switching from stereo to mono halves the bitrate, which is often the simplest way to reduce file size for a single microphone.

Each setting scales the result in a straight line. Doubling the sample rate, the bit depth or the channel count doubles the bitrate. Moving from 16-bit to 24-bit raises it by half.

Check the output

To confirm your figures, open the file details in your audio editor or a media inspection tool and compare the reported sample rate, bit depth, channel count and bitrate with the values you used. For PCM, the reported bitrate should match your calculation exactly. If it does not, one of the input values is different from what you assumed.

You can also compare the actual file size with your estimate. A PCM file is slightly larger than the calculated audio data, because the container adds a header and may store metadata such as markers, loop points or embedded artwork. A small difference is expected; a difference of about half or double usually points to a wrong channel count or bit depth.

Keep in mind what the number does and does not tell you. Bitrate describes how much data the format stores, not how good the recording sounds. A higher bit depth gives more headroom and a lower noise floor in the format itself, but it will not remove background noise picked up by the microphone or fix an input level that is set too low or clipping.

Common problems and next steps

Result is eight times too large or too small. Bitrate is measured in bits, file size in bytes. Divide bits by 8 to get bytes, and check that you did not mix kbps (kilobits) with kB/s (kilobytes).

File size does not match the kilobyte or megabyte figure shown by your system. Some systems display sizes in binary units, where one kilobyte is treated as 1,024 bytes rather than 1,000. The underlying byte count is the same; only the unit differs. Audio bitrates are normally quoted with 1 kbps equal to 1,000 bits per second.

24-bit file is larger than expected. Some software stores 24-bit samples inside 32-bit containers, so each sample takes 32 bits on disk. Use the stored size per sample in the formula when estimating file size. The same applies to 32-bit floating-point audio, which uses 32 bits per sample.

Recording settings differ from what you selected. Your operating system, audio interface and recording or video call app can each have their own sample rate setting for the same input device. If they disagree, audio may be resampled before it is saved, and the file can end up with a different sample rate than you expected. Check the format in each place and keep them consistent.

Formula gives the wrong answer for a compressed file. Lossy formats like MP3 and AAC use a target bitrate chosen at encoding time, and lossless FLAC produces a variable bitrate that depends on the content. For these, read the bitrate from the file details instead of calculating it. If you need a smaller file, the practical options within PCM are to lower the sample rate, reduce bit depth or record in mono; otherwise convert to a compressed format and accept that its bitrate is set by the encoder.