Building Occupancy Load Calculator

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Building Occupancy Load Calculator

Calculate the maximum occupancy load for a building space based on floor area and occupancy type per the International Building Code (IBC) Table 1004.5.

Floor Area (sq ft)

Area Measurement

Square Feet (sq ft) Square Meters (m²)

Occupancy Type (IBC Table 1004.5)

Assembly – Concentrated (chairs only) — 7 sq ft/person Assembly – Unconcentrated (tables & chairs) — 15 sq ft/person Assembly – Standing space — 5 sq ft/person Assembly – Waiting areas — 5 sq ft/person Assembly – Gaming floors — 11 sq ft/person Assembly – Stages & platforms — 15 sq ft/person Assembly – Bleachers — 3 sq ft/person

Business – Office areas — 150 sq ft/person Business – Courtrooms — 40 sq ft/person

Educational – Classroom — 20 sq ft/person Educational – Shops, labs, vocational — 50 sq ft/person

Exercise rooms — 50 sq ft/person Swimming pools (water area) — 50 sq ft/person Swimming pool decks — 30 sq ft/person Skating rinks — 50 sq ft/person

Healthcare – Inpatient treatment areas — 240 sq ft/person Healthcare – Outpatient areas — 100 sq ft/person Healthcare – Sleeping areas — 120 sq ft/person

Industrial – General & high-hazard — 100 sq ft/person Industrial – Special-purpose — Occupant load per design

Institutional – Residential care — 120 sq ft/person Institutional – Sleeping areas — 120 sq ft/person

Mercantile – Basement & grade floor — 30 sq ft/person Mercantile – Upper floors — 60 sq ft/person Mercantile – Storage, stock, shipping — 300 sq ft/person

Residential – Hotels & apartments — 200 sq ft/person Residential – Dormitories — 50 sq ft/person

Storage – General — 300 sq ft/person

Number of Floors / Spaces

Calculate Occupancy Load

function buiCalc() { var resultDiv = document.getElementById('bui-result');

// --- Inputs --- var areaRaw = parseFloat(document.getElementById('bui-area').value); var unit = document.getElementById('bui-unit').value; var occupancy = document.getElementById('bui-occupancy').value; var floors = parseInt(document.getElementById('bui-floors').value);

// --- Validation --- if (isNaN(areaRaw) || areaRaw ⚠ Please enter a valid floor area greater than 0.'; return; } if (isNaN(floors) || floors ⚠ Number of floors must be at least 1.'; return; }

// --- Unit conversion: always work in sq ft --- var areaSqFt = (unit === 'sqm') ? areaRaw * 10.7639 : areaRaw;

// --- Load factors (sq ft per person) per IBC Table 1004.5 --- var loadFactors = { assembly_concentrated : 7, assembly_unconcentrated: 15, assembly_standing : 5, assembly_waiting : 5, assembly_gaming : 11, assembly_stages : 15, assembly_bleachers : 3, business_office : 150, business_courtrooms : 40, edu_classroom : 20, edu_shops : 50, exercise_gym : 50, exercise_pool : 50, exercise_pool_deck : 30, exercise_skating : 50, health_inpatient : 240, health_outpatient : 100, health_sleeping : 120, industrial_general : 100, industrial_special : null, inst_residential : 120, inst_sleeping : 120, mercantile_basement : 30, mercantile_upper : 60, mercantile_storage : 300, residential_hotel : 200, residential_dormitory : 50, storage_general : 300 };

var factor = loadFactors[occupancy];

if (factor === null) { resultDiv.innerHTML = '⚠ Special-purpose industrial occupancy load must be determined by a licensed engineer based on actual operations. No standard sq ft/person factor applies per IBC.'; return; }

// --- Core formula: Occupancy Load = Floor Area (sq ft) / Load Factor (sq ft/person) --- // Per IBC 1004.1: fractional numbers shall be rounded up to the next whole number. var occupancyPerFloor = Math.ceil(areaSqFt / factor); var totalOccupancy = occupancyPerFloor * floors;

// --- Egress width check (IBC 1005.1): 0.2 in/person for stairs, 0.15 in/person for other egress --- var minStairWidthIn = totalOccupancy * 0.2; // inches var minEgressWidthIn = totalOccupancy * 0.15; // inches var minStairWidthFt = (minStairWidthIn / 12).toFixed(2); var minEgressWidthFt = (minEgressWidthIn / 12).toFixed(2);

// --- Display area in both units --- var areaSqM = (unit === 'sqm') ? areaRaw : (areaSqFt / 10.7639);

resultDiv.innerHTML = '### Results ' + '' + 'Floor Area (per floor)' + '' + areaSqFt.toFixed(2) + ' sq ft (' + areaSqM.toFixed(2) + ' m²)' + 'IBC Load Factor' + '' + factor + ' sq ft / person' + 'Occupancy Load (per floor)' + '' + occupancyPerFloor + ' persons' + 'Number of Floors / Spaces' + '' + floors + '' + 'Total Occupancy Load' + '' + totalOccupancy + ' persons' + 'Min. Stair Egress Width (IBC 1005.1)' + '' + minStairWidthIn.toFixed(1) + ' in (' + minStairWidthFt + ' ft)' + 'Min. Other Egress Width (IBC 1005.1)' + '' + minEgressWidthIn.toFixed(1) + ' in (' + minEgressWidthFt + ' ft)' + '' + '⚠ Results are estimates. Always verify with a licensed architect or engineer and local AHJ (Authority Having Jurisdiction).

'; }

#### Formula

Occupancy Load (per floor) = ⌈ Floor Area (sq ft) ÷ Load Factor (sq ft/person) ⌉

Total Occupancy Load = Occupancy Load per Floor × Number of Floors

Per IBC Section 1004.1, fractional occupant loads are rounded up to the next whole number (ceiling function).

Minimum Egress Width (IBC 1005.1):

Unit Conversion: 1 m² = 10.7639 sq ft

#### Assumptions & References

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References

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