Source: https://guthlabs.ai/docs/instruments/rule-of-72-70-114-estimator/implementation/

instrument implementation / implementation-contract

# Rule of 72 / 70 / 114 Estimator implementation

A source-bound implementation contract for Rule of 72 / 70 / 114 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**: t4-116

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero annual rate makes every formula undefined, so the instrument must reject it. A convention mismatch between percentage points and decimal fractions can also produce results differing by a factor of 100. Negative or nonpositive rates should likewise be validated because the raw arithmetic can produce meaningless negative or undefined times.

## 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": {
    "rate_percent": 6
  },
  "expected_outputs": {
    "years_to_double_rule72": 12,
    "years_to_triple_rule114": 19,
    "years_to_double_rule70": 11.6666666667
  },
  "working": "Double using Rule 72: 72 ÷ 6 = 12 years. Triple using Rule 114: 114 ÷ 6 = 19 years. Alternate double using Rule 70: 70 ÷ 6 = 11.6666666667 years."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/rule-of-72-70-114-estimator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/rule-of-72-70-114-estimator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/rule-of-72-70-114-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-tranche4/tranche4-results.json`