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
Percentage of floor area usable for seating after accounting for aisles, exits, and stage.Seating Configuration
Distance from the back of one seat to the back of the next row. Typical: 1.5 (comfortable) – 2.5 (normal) – 4.0 (crowded). Only used for standing/mixed layouts.Sightline Parameters
Height of the stage above the audience floor level. Typical seated eye height: 1.12 m. Vertical rise of the floor between consecutive rows (rake). 0 = flat floor.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
- D = horizontal distance from spectator's eye to the focal point (stage front) (m)
- T = row depth / seat pitch (m)
- H = eye height of spectator above the stage surface level (m) = (floor elevation + seated eye height) − stage height
- C = vertical clearance over the head of the spectator in the row directly in front (m)
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
- Usable area efficiency accounts for aisles, emergency exits, stage footprint, and circulation space (typically 60–80%).
- Standard seated eye height is 1.12 m (BS 6206 / IASS WG7 guidance).
- Minimum C-value of 60 mm is the widely accepted threshold for acceptable sightlines in theatres and stadia (IASS Working Group 7; Geraint John & Rod Sheard, Stadia: A Design and Development Guide).
- Standing density: 1.5 persons/m² (comfortable), 2.5 (normal event), 4.0 (crowded/festival) per The Event Safety Guide (Purple Guide), UK.
- Seat pitch (row depth) of 0.85 m is a common minimum for fixed theatre seating; 0.90–1.0 m for premium comfort.
- The C-value formula assumes a flat rake increment per row. Curved or variable-rake seating requires row-by-row geometric modelling.
- This calculator does not account for structural columns, balcony overhangs, or curved seating bowls.
- References: BS EN 13200-1 (Spectator facilities); IASS WG7 Sightlines; Building Regulations Part B (fire capacity limits).