Source: https://guthlabs.ai/docs/instruments/eoq-inventory-reorder-calculator/implementation/

instrument implementation / implementation-contract

# EOQ / Inventory Reorder Calculator implementation

A source-bound implementation contract for EOQ / Inventory Reorder Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_WITH_ERRATA**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-with-binding-errata

**Evidence ID**: t5-063

**Effect**: Computation or source lookup only

## Input and validation requirements

The calculator should reject H=0 because EOQ divides by zero, and should reject negative annual demand because the EOQ square-root argument becomes negative. In addition, the unspecified annual-to-daily conversion convention changes the reorder point: 105 units using 365 days versus 106.388888888889 units using 360 days.

## Required corrections

````
[
  {
    "vector": 1,
    "field": "annual_relevant_total_cost",
    "wrong": 1800,
    "correct": 1200,
    "cause": "working writes 600+600=1800; her own v2 formula is correct"
  }
]
````

## Inspectable interface fixture

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

````
{
  "inputs": {
    "annual_demand_D_units_per_year": 7200,
    "order_cost_S_currency_per_order": 50,
    "holding_cost_H_currency_per_unit_per_year": 2,
    "lead_time_days": 14,
    "safety_stock_units": 80
  },
  "expected_outputs": {
    "eoq_units": 600,
    "reorder_point_units": 356.1643836,
    "orders_per_year": 12,
    "annual_relevant_total_cost_currency": 1800
  },
  "working": "EOQ = √(2×7200×50/2) = √360000 = 600 units. Daily demand = 7200/365 = 19.7260274 units/day. Reorder point = 19.7260274×14+80 = 276.1643836+80 = 356.1643836 units. Orders/year = 7200/600 = 12. Ordering cost = 12×50 = 600. Holding cost = (600/2)×2 = 600. Total relevant annual cost = 600+600 = 1800."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/eoq-inventory-reorder-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/eoq-inventory-reorder-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/eoq-inventory-reorder-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-tranche5/tranche5-results.json`

- `tranche errata record`