Source: https://guthlabs.ai/docs/instruments/rebar-area-spacing-calculator/implementation/

instrument implementation / implementation-contract

# Rebar Area / Spacing Calculator implementation

A source-bound implementation contract for Rebar Area / Spacing Calculator; 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**: t7-100

**Effect**: Computation or source lookup only

## Input and validation requirements

Zero width produces zero spacing and an undefined bars-per-meter result; one bar produces division by zero in spacing; negative width has conflicting signed versus geometric interpretations; and the two calculation modes require explicit selection.

## 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": {
    "mode": "area_and_spacing_from_count",
    "bar_size": "#4",
    "number_of_bars": 10,
    "width_in": 108
  },
  "expected_outputs": {
    "As_total_in2": 2,
    "spacing_in": 12,
    "bars_per_meter": 3.280839895
  },
  "reference_data": {
    "rebar_nominal_area_in2": {
      "#4": 0.2
    },
    "inch_to_meter": 0.0254,
    "source_convention": "US rebar nominal-area table, widely tabulated standard value consistent with ASTM A615/ACI practice; inch-to-meter conversion is the exact SI definition."
  },
  "working": "As = n·Ab = 10·0.20 in² = 2.00 in². Spacing = width/(n−1) = 108 in/(10−1) = 108/9 = 12.00 in. Convert spacing: 12.00 in·0.0254 m/in = 0.3048 m. Bars per meter = 1/0.3048 m = 3.280839895 bars/m."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/rebar-area-spacing-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/rebar-area-spacing-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/rebar-area-spacing-calculator/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-tranche7/tranche7-results.json`