Source: https://guthlabs.ai/docs/instruments/hydration-needs-estimator/mechanism/

instrument mechanism / verified-clean

# Hydration Needs Estimator mechanism

The inspectable method record for Hydration Needs Estimator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The arithmetic is valid under the stated assumptions, but the specification is not implementation-deterministic because activity-rate selection and climate_add are undefined. Define the climate algorithm, exercise-intensity mapping, input bounds, and ounce convention before release.

- The activity adjustment is specified only as a broad range of 500-1000 ml/hr; the formula does not define how exercise intensity selects a rate within that range.

- The formula does not explicitly state that activity_add equals exercise_duration_hours multiplied by an activity rate in ml/hr.

- climate_add is undefined: there is no temperature threshold, climate category, or numeric adjustment.

- The 35 ml/kg/day baseline is a general rule of thumb, not a universally valid hydration requirement; it should not be presented as an individualized or clinically validated target.

- Adding a fixed exercise amount to the baseline may not account for individual sweat rate, exercise conditions, or fluid intake from food and other beverages.

## Units and conventions

- body weight is entered in kilograms.

- The baseline result is milliliters per day: weight_kg × 35 ml/kg/day.

- Exercise duration is measured in hours.

- activity_add is interpreted as exercise_duration_hours × activity_rate_ml_per_hr.

- The activity rate is assumed to be between 500 and 1000 ml/hr, inclusive.

- climate_add is interpreted as an explicitly supplied number of milliliters per day; its calculation is not defined by the specification.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "weight_kg": 70,
    "activity_duration_hr": 1,
    "activity_rate_ml_per_hr": 750,
    "climate_add_ml": 500
  },
  "expected_outputs": {
    "baseline_ml": 2450,
    "activity_add_ml": 750,
    "total_ml": 3700,
    "total_us_fl_oz": 125.11
  },
  "working": "baseline = 70 × 35 = 2450 ml/day; activity_add = 1 × 750 = 750 ml; total = 2450 + 750 + 500 = 3700 ml/day; US fl oz = 3700 ÷ 29.5735 = 125.112..., rounded to 125.11 fl oz."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specification has no explicit validation for zero or non-finite inputs, can produce Infinity for extreme magnitudes, does not define the activity-intensity branch within the 500-1000 ml/hr range, and leaves weight units and climate_add calculation ambiguous.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/hydration-needs-estimator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/hydration-needs-estimator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/hydration-needs-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`

- `BOUNDARY_HAZARD_CATALOG.json`