Source: https://guthlabs.ai/docs/instruments/bit-rate-file-size-for-audio-codecs-mp3-aac-flac-estimate/implementation/

instrument implementation / implementation-contract

# Bit Rate ↔ File Size for Audio Codecs (MP3/AAC/FLAC estimate) implementation

A source-bound implementation contract for Bit Rate ↔ File Size for Audio Codecs (MP3/AAC/FLAC estimate); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-115

**Effect**: Computation or source lookup only

## Input and validation requirements

An extreme but numerically representable input overflows ordinary JavaScript floating-point arithmetic and produces Infinity instead of a finite size. The convention probe also exposes materially different displayed values if decimal and binary bitrate or storage units are mixed.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "codec": "MP3",
    "bitrate_bps": 128000,
    "duration_seconds": 180
  },
  "expected_outputs": {
    "estimated_size_bytes": 2880000,
    "estimated_size_MB_decimal": 2.88,
    "estimated_size_MiB": 2.74658203125
  },
  "working": "size = bitrate × duration ÷ 8\n= 128,000 bits/s × 180 s ÷ 8\n= 23,040,000 bits ÷ 8\n= 2,880,000 bytes\n= 2.88 MB decimal\n= 2,880,000 ÷ 1,048,576\n= 2.74658203125 MiB"
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/bit-rate-file-size-for-audio-codecs-mp3-aac-flac-estimate/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/bit-rate-file-size-for-audio-codecs-mp3-aac-flac-estimate/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/bit-rate-file-size-for-audio-codecs-mp3-aac-flac-estimate/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`