Venue Capacity and Sightline Calculator

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.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }

Venue Capacity and Sightline Calculator

Calculate the seating capacity of a venue and evaluate sightline quality based on C-value (the vertical distance between a spectator's eye and the sightline over the head of the person in front).

### Venue Dimensions

Venue Floor Width (m)

Venue Floor Depth (m)

Usable Area Efficiency (%)

Percentage of floor area usable for seating after accounting for aisles, exits, and stage.

### Seating Configuration

Seat Width (m)

Row Depth / Seat Pitch (m)

Distance from the back of one seat to the back of the next row.

Layout Type

Fixed Seating (chairs/seats) Standing Room Mixed (50% seated / 50% standing)

Standing Density (persons/m²)

Typical: 1.5 (comfortable) – 2.5 (normal) – 4.0 (crowded). Only used for standing/mixed layouts.

### Sightline Parameters

Stage / Performance Surface Height (m)

Height of the stage above the audience floor level.

Distance from Stage to First Row (m)

Seated Eye Height (m)

Typical seated eye height: 1.12 m.

Floor Rise per Row (m)

Vertical rise of the floor between consecutive rows (rake). 0 = flat floor.

Number of Rows to Analyse

Calculate

function venCalc() { // --- Inputs --- const floorWidth = parseFloat(document.getElementById('ven-floor-width').value); const floorDepth = parseFloat(document.getElementById('ven-floor-depth').value); const efficiency = parseFloat(document.getElementById('ven-area-efficiency').value); const seatWidth = parseFloat(document.getElementById('ven-seat-width').value); const rowDepth = parseFloat(document.getElementById('ven-row-depth').value); const layoutType = document.getElementById('ven-layout-type').value; const standDensity = parseFloat(document.getElementById('ven-standing-density').value); const stageH = parseFloat(document.getElementById('ven-stage-height').value); const firstRowDist = parseFloat(document.getElementById('ven-first-row-dist').value); const eyeH = parseFloat(document.getElementById('ven-eye-height').value); const floorRise = parseFloat(document.getElementById('ven-floor-rise').value); const numRows = parseInt(document.getElementById('ven-num-rows').value);

const resultDiv = document.getElementById('ven-result');

// --- Validation --- const errors = []; if (isNaN(floorWidth) || floorWidth 100) errors.push("Usable area efficiency must be between 10% and 100%."); if (isNaN(seatWidth) || seatWidth 5.0) errors.push("Standing density must be between 0.5 and 5.0 persons/m²."); if (isNaN(stageH) || stageH 0) { resultDiv.style.display = 'block'; resultDiv.innerHTML = 'Please fix the following errors:' + errors.map(e => '').join('') + ''; return; }

// ============================================= // CAPACITY CALCULATION // ============================================= const totalArea = floorWidth * floorDepth; // m² const usableArea = totalArea * (efficiency / 100); // m²

// Seats per row = floor(usable width / seat width) // Rows = floor(usable depth / row depth) // Using square-root split for a rectangular block approximation const seatsPerRow = Math.floor(floorWidth * (efficiency / 100) / seatWidth); const totalRows = Math.floor(floorDepth * (efficiency / 100) / rowDepth); const fixedCapacity = seatsPerRow * totalRows;

const standingCapacity = Math.floor(usableArea * standDensity);

let capacity, capacityLabel; if (layoutType === 'fixed') { capacity = fixedCapacity; capacityLabel = 'Fixed Seating Capacity'; } else if (layoutType === 'standing') { capacity = standingCapacity; capacityLabel = 'Standing Room Capacity'; } else { // Mixed: half area seated, half standing const halfArea = usableArea / 2; const mixedSeated = Math.floor((floorWidth * (efficiency/100) / seatWidth)) * Math.floor((halfArea / (floorWidth * (efficiency/100))) / rowDepth); const mixedStanding = Math.floor(halfArea * standDensity); capacity = mixedSeated + mixedStanding; capacityLabel = 'Mixed Layout Capacity (seated + standing)'; }

// ============================================= // SIGHTLINE C-VALUE CALCULATION // C = (D + T) * (N / D) - N // where: // D = horizontal distance from spectator eye to focal point (stage front) // T = row depth (seat pitch) // N = C-value of previous row (or initial N for row 1) // C = vertical clearance over the head of the person in front // // For row r (1-indexed): // horizontal distance D_r = firstRowDist + (r-1) * rowDepth // floor height at row r = (r-1) * floorRise // eye height at row r = floor height + eyeH // sightline target height = stageH (top of stage / performance point) // // C-value formula (ISO/IASS standard): // C_r = (D_r + T) * (H_r / D_r) - H_r // where H_r = eye height at row r above stage level // = (eyeH + (r-1)*floorRise) - stageH [can be negative if stage is high] // // Minimum acceptable C-value: 60 mm (0.06 m) per standard guidance. // =============================================

const MIN_C = 0.06; // metres let sightlineRows = []; let goodRows = 0, poorRows = 0;

for (let r = 1; r = MIN_C) { quality = 'Good ✓'; goodRows++; } else { quality = 'Poor ✗'; poorRows++; }

sightlineRows.push({ row: r, dist: D_r.toFixed(2), eyeElev: eyeElevation.toFixed(3), H_r: H_r.toFixed(3), C_r: C_r !== null ? (C_r * 1000).toFixed(1) : '—', // mm angle: sightlineAngle.toFixed(1), quality: quality }); }

const overallSightline = poorRows === 0
? '✅ All rows have acceptable sightlines.'
('⚠️ ' + poorRows + ' of ' + numRows + ' rows have poor sightlines (C '' + '' + r.row + '' + '' + r.dist + '' + '' + r.eyeElev + '' + '' + r.H_r + '' + '' + r.C_r + '' + '' + r.angle + '°' + '' + r.quality + '' + '' ).join('');

resultDiv.style.display = 'block'; resultDiv.innerHTML = '### Results ' +

'#### 📐 Venue Capacity ' + '' + 'ParameterValue' + 'Total Floor Area' + totalArea.toFixed(1) + ' m²' + 'Usable Area (' + efficiency + '%)' + usableArea.toFixed(1) + ' m²' + (layoutType !== 'standing' ? 'Seats per Row' + seatsPerRow + '' : '') + (layoutType !== 'standing' ? 'Total Rows (fixed)' + totalRows + '' : '') + '' + capacityLabel + '' + capacity.toLocaleString() + ' persons' + '' +

'#### 👁️ Sightline Analysis (C-Value per Row) ' + '' + overallSightline + '

' + '' + '' + 'RowDist to Stage (m)Eye Elev. (m)H (m)C-Value (mm)Sightline AngleQuality' + tableRows + '' + '' + 'C-Value: vertical clearance over the head of the spectator in the row in front. Minimum acceptable: 60 mm.

'; }

#### Formulas Used

Capacity (Fixed Seating):

Usable Area = Floor Width × Floor Depth × (Efficiency / 100)

Seats per Row = ⌊(Usable Width / Seat Width)⌋

Number of Rows = ⌊(Usable Depth / Row Depth)⌋

Capacity = Seats per Row × Number of Rows

Capacity (Standing):

Capacity = Usable Area × Standing Density

Sightline C-Value (ISO/IASS standard):

C = (D + T) × (H / D) − H

Minimum acceptable C-value: 60 mm (standard guidance for theatres and stadia).

Sightline Angle:

θ = arctan(H / D) — angle of the sightline above horizontal.

#### Assumptions & References

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References

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