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MP3 Bitrate Calculator

Calculate audio file size from bitrate and duration, or find the required bitrate to hit a target file size. Supports lossy formats (MP3, AAC, Opus, Vorbis) with format-aware quality assessment, plus lossless (FLAC, WAV) computed from PCM parameters.

Input

Format

Bitrate

kbps

PCM Parameters (WAV / FLAC source)

FLAC Compression Ratio (fraction of PCM)

ratio

Common MP3 Bitrates

Target File Size

MB

Duration

Result

File Size / Bitrate

—

Effective Bitrate

—

Size (binary)

—

Per Minute

—

Per Hour

—

Formulas

Lossy: bytes = (bitrate_kbps × 1000 / 8) × duration_sec

PCM/WAV: bytes = SR × (bits/8) × channels × duration_sec

FLAC: PCM bytes × compression ratio (~0.5–0.7)

Reverse: bitrate_kbps = (bytes × 8) / (duration_sec × 1000)

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3-Minute Stereo File Size by Format & Bitrate

Format @ bitrate	Bitrate	3 min file	1 hour file
MP3 64 kbps	64 kbps	~1.44 MB	~28.8 MB
MP3 96 kbps	96 kbps	~2.16 MB	~43.2 MB
MP3 128 kbps	128 kbps	~2.88 MB	~57.6 MB
MP3 192 kbps	192 kbps	~4.32 MB	~86.4 MB
MP3 256 kbps	256 kbps	~5.76 MB	~115.2 MB
MP3 320 kbps (max)	320 kbps	~7.20 MB	~144.0 MB
AAC 128 kbps (≈ MP3 192)	128 kbps	~2.88 MB	~57.6 MB
AAC 256 kbps	256 kbps	~5.76 MB	~115.2 MB
Opus 96 kbps (≈ MP3 192)	96 kbps	~2.16 MB	~43.2 MB
Opus 128 kbps	128 kbps	~2.88 MB	~57.6 MB
FLAC 44.1k/16-bit stereo	~847 kbps	~19.05 MB	~381.0 MB
FLAC 96k/24-bit stereo	~2,765 kbps	~62.21 MB	~1.24 GB
WAV 44.1k/16-bit stereo	1,411 kbps	~31.75 MB	~635.0 MB
WAV 96k/24-bit stereo	4,608 kbps	~103.7 MB	~2.07 GB

About Audio Bitrate & File Size

Bitrate is how many bits of audio data are stored per second, expressed in kilobits per second (kbps) or megabits per second (Mbps). File size scales linearly with bitrate × duration. The conversion is direct: bytes = (bitrate_kbps × 1000 / 8) × duration_sec.

Lossy vs lossless

Lossy formats (MP3, AAC, Opus, Vorbis) discard psychoacoustically-imperceptible information to reach low bitrates with subjective quality near the original. Lossless formats (FLAC, ALAC, APE) use entropy coding to compress the exact PCM signal — typically achieving 50–70% of WAV size with bit-perfect reconstruction. Uncompressed PCM (WAV, AIFF) stores raw samples — biggest files but trivial to process.

Format efficiency: AAC and Opus beat MP3

At equivalent perceptual quality, AAC needs about 70% of MP3's bitrate, and Opus about 50–60% of MP3's. So AAC 128 kbps roughly matches MP3 192 kbps, and Opus 96 kbps matches MP3 192. For new projects, Opus is technically the best lossy choice; AAC remains the de facto streaming standard (Apple, YouTube, Spotify); MP3 persists for backward compatibility.

Picking a target bitrate

For background music or podcasts: 96–128 kbps (MP3) is fine. For careful listening: 192–256 kbps. For audiophile-grade or master copies: lossless. The 320 kbps MP3 ceiling is "transparent" for most listeners — anything above adds bytes with diminishing perceptual return.

Frequently Asked Questions

How big is a 3-minute MP3 at 192 kbps?

Bitrate × duration ÷ 8 gives bytes. For 192 kbps × 180 seconds: 192,000 bits/s × 180 s = 34,560,000 bits ÷ 8 = 4,320,000 bytes = 4.32 MB. For a 5-minute song at 192 kbps: 7.2 MB. For an album of ten 4-minute tracks: ~57.6 MB.

How do I calculate the bitrate from a known file size?

Reverse the formula: bitrate_kbps = (file_size_bytes × 8) / (duration_sec × 1000). Example: a 5 MB 3-minute file → (5,000,000 × 8) / (180 × 1000) = 40,000 / 180 ≈ 222 kbps. Switch to "Size → Bitrate" mode on this tool to do it automatically.

Why is Opus more efficient than MP3?

Opus (released 2012) uses modern psychoacoustic models, adaptive bitrate, and a flexible CELT+SILK hybrid codec. MP3 (1993) was designed for the computing power of the early 1990s. Opus achieves roughly the same perceptual quality as MP3 at half the bitrate — a 128 kbps Opus file sounds about as good as a 192–256 kbps MP3 on most material.

What's a typical FLAC file size?

FLAC achieves about 50–70% of WAV size depending on content (more compression for sparse content like solo voice; less for dense orchestral). A 3-minute CD-quality stereo track (16-bit / 44.1 kHz, ~31.75 MB WAV) typically compresses to 16–22 MB FLAC. Average ratio: ~0.6 (60% of WAV).

Is 320 kbps MP3 lossless?

No — MP3 is always lossy, regardless of bitrate. 320 kbps is the maximum standard MP3 bitrate ("CBR 320"), and it's typically described as "transparent" for most listeners — but spectrum analysis shows MP3 still discards some high-frequency content. For true bit-perfect reproduction, use FLAC or other lossless codecs.

How much does a 10-hour audiobook take?

At 64 kbps (typical voice-only MP3): 10 hours × 3600 s × 64 / 8 × 1000 / 1e6 = 288 MB. At 96 kbps: 432 MB. At 128 kbps: 576 MB. Voice content compresses much better than music — 64 kbps stereo is often indistinguishable from higher rates for narrated content. Audible.com uses 64 kbps mono AAC by default.

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