Source: https://guthlabs.ai/docs/instruments/race-time-predictor-riegel-formula/implementation/

instrument implementation / implementation-contract

# Race Time Predictor (Riegel Formula) implementation

A source-bound implementation contract for Race Time Predictor (Riegel Formula); 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**: t4-211

**Effect**: Computation or source lookup only

## Input and validation requirements

Zero or negative/invalid distances can produce undefined results, and a zero target distance produces an undefined pace even though the time expression evaluates mathematically to zero. The specification does not state input validation or unit conventions, creating rejection and interpretation hazards.

## 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": {
    "known_distance": 5,
    "known_distance_unit": "km",
    "known_time": 25,
    "known_time_unit": "min",
    "target_distance": 10,
    "target_distance_unit": "km"
  },
  "expected_outputs": {
    "predicted_time_min": 52.1233,
    "predicted_pace_min_per_km": 5.2123
  },
  "working": "D2/D1 = 10/5 = 2. T2 = 25 × 2^1.06 = 25 × 2.08493 = 52.1233 min. Pace = T2/D2 = 52.1233/10 = 5.2123 min/km."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/race-time-predictor-riegel-formula/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/race-time-predictor-riegel-formula/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/race-time-predictor-riegel-formula/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-tranche4/tranche4-results.json`