# Event Seating Capacity Calculator

> Estimate how many chairs fit in a room in theatre-style rows from its size, seat width, row spacing, aisles and the space kept clear at the front and back.

Category: Everyday tools · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/event-seating-capacity-calculator

Theatre-style capacity is seats per row times rows: the width left after aisles divided by the seat width, and the depth left after clearances divided by the row spacing.

Also called: Chair layout calculator, Theatre-style capacity calculator.

## Inputs
- Room width (across the rows) (default 20)
- Room depth (front to back) (default 30)
- Stage and front clearance (default 5; optional)
- Rear clearance (cross aisle) (default 2; optional)
- Seat width, centre to centre (default 0.5)
- Row spacing, back to back (default 0.9)
- Number of aisles (default 2; optional)
- Width of each aisle (default 1.2; optional)

## Results
- Seats that fit
- Seats per row
- Rows
- Room area per seat (your unit squared)
- Share of the floor used by seating blocks

## Formula

```
Seats per row = ⌊(Width − Aisles × Aisle width) ÷ Seat width⌋;  Rows = ⌊(Depth − Front − Rear) ÷ Row spacing⌋;  Seats = Seats per row × Rows
```

Where:
- Seat width: chair width plus any gap, centre to centre
- Row spacing: distance from the back of one row to the back of the next

## Worked example
1. Width for seats = 20 − 2 × 1.2 = 17.6 m; 17.6 ÷ 0.5 = 35.2, so 35 per row.
2. Depth for rows = 30 − 5 − 2 = 23 m; 23 ÷ 0.9 = 25.6, so 25 rows.
3. Seats = 35 × 25 = 875.

**Result:** A 20 × 30 m room with a 5 m stage zone, two 1.2 m aisles, 0.5 m chairs and 0.9 m rows seats 875 people theatre-style.

## What the result means

This is a geometric fit. The number you may actually admit is the lower of this figure and the legal occupancy limit set for the room by the fire or building authority.

## Assumptions and limits
- A rectangular room with straight rows and aisles running front to back.
- All lengths are in the same unit.
- Fire codes also limit seats per row between aisles, exit widths and travel distances; these are not checked here.
- Pillars, AV desks and wheelchair spaces must be subtracted separately.

## Questions

### How much space per person for theatre seating?

The answer here shows it for your layout. Planners often work from a figure per person, but codes and venues differ, so use your own measurements.

### Does this give the legal capacity?

No. Only the authority that licenses the venue sets its maximum occupancy.

## Related calculators
- [Venue Occupancy Calculator](https://calculators.geekmidst.com/calculators/venue-occupancy-calculator)
- [Area Calculator](https://calculators.geekmidst.com/calculators/area-calculator)
- [Length Converter](https://calculators.geekmidst.com/calculators/length-converter)

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/event-seating-capacity-calculator