Source: https://guthlabs.ai/docs/instruments/reading-time-estimator/implementation/

instrument implementation / implementation-contract

# Reading Time Estimator implementation

A source-bound implementation contract for Reading Time Estimator; 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**: t5-051

**Effect**: Computation or source lookup only

## Input and validation requirements

- Division by zero occurs if wpm is 0; reject zero before calculation.

- Negative WPM is invalid and should be rejected.

- Negative word counts are invalid and should be rejected.

- Text word-counting behavior is ambiguous unless tokenization rules are explicitly defined.

- Very short texts can produce fractional minutes and should not be rounded to whole minutes before converting to seconds.

- A selected default must be an exact positive number, not the range 200-250.

## 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": {
    "word_count": 500,
    "wpm": 250
  },
  "expected_outputs": {
    "time_min": 2,
    "time_seconds": 120
  },
  "working": "time_min = word_count / wpm = 500 / 250 = 2 minutes. time_seconds = 2 × 60 = 120 seconds."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/reading-time-estimator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/reading-time-estimator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/reading-time-estimator/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`