Venue Capacity Calculator for Martyn's Law

Work out whether your venue falls under the standard tier (200-799), enhanced tier (800+), or is out of scope entirely. This free calculator uses Approved Document B floor space factors and exit width analysis.

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Calculate Your Venue Capacity

Step 1: Choose Your Calculation Method

The Act accepts several methods for determining your expected numbers. This calculator supports the two most common.

Step 2: Add Your Room Zones

Divide your venue into zones by use type. Each zone uses a different occupancy density factor. Exclude stair enclosures, lifts, toilets, corridors, and plant rooms from the area.

Can't see your room type? Pick the closest match. That's what the official fire safety guidance says to do when a use isn't listed.

Zone 1

Name (optional)

Room Type

Floor Area (m²)

Step 3: Add Your Exits

Measure the clear opening width of each exit in millimetres. Your final capacity is the lower of the floor space figure and the exit figure.

Exit 1

Name (optional)

Clear Width (mm)

Opens inward

Step 4: Add Staff Count

Martyn's Law capacity includes everyone on site: customers, staff, volunteers, and contractors. Enter the maximum number of staff you would expect on site at the same time during your busiest period.

Maximum Staff on Site

How Does Capacity Work Under Martyn's Law?

The Terrorism (Protection of Premises) Act 2025 does not use a strict mathematical capacity definition. Instead, it asks for the “greatest number of individuals reasonably expected to be present at the same time”. This includes everyone: customers, staff, volunteers, and contractors.

The thresholds are straightforward. Under 200 people and you're out of scope. Between 200 and 799 puts you in the standard tier. 800 or more means enhanced tier.

For a detailed overview of what the law requires, see our complete guide to Martyn's Law compliance.

What Are the Six Accepted Assessment Methods?

The official GOV.UK factsheet sets out six acceptable ways to determine your numbers.

Fire safety occupancy figures: floor space density factors and exit capacity analysis (the lower of the two). This is what the calculator above uses.
Historical attendance data: actual records of attendance (door counts, CCTV, manual counts) plus staff.
Fixed seating or standing positions: count of seats and designated standing areas plus staff.
Tickets and pre-registration: maximum tickets issued for any session. Staff are included only if not already counted in the ticket figure.
Imposed restrictions: caps set by entertainment licences, planning conditions, or other regulatory limits plus staff.
Other reasonable methods: EPOS transaction data, customer flow assessments, or any other reasonable evidence with justification.

The government is clear that venues should not need to pay consultants for this. It should be a straightforward self-assessment.

Floor Space Factors (Approved Document B, Table D1)

These are the standard occupancy densities from Building Regulations Approved Document B. Divide your usable floor area by the relevant factor to get the maximum number of people per zone.

Room / Use Type	m² per Person
Standing spectator areas, bar areas within 2m of serving point	0.3
Dance floor, nightclub, pop concert, bar (no fixed seating)	0.5
Concourse or queuing area	0.7
Dining room, restaurant, lounge, meeting room, bar	1.0
Exhibition hall or studio	1.5
Shop (main sales area), hairdresser	2.0
Art gallery, museum, workshop	5.0
Office	6.0
Shop (furniture, appliances, wholesale)	7.0
Kitchen or library	7.0

Source: Approved Document B, Volume 2. Exclude stair enclosures, lifts, toilets, corridors, and plant rooms from your area measurements.

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How Do Exit Widths Affect Capacity?

Your fire safety capacity is the lower of two figures: the floor space calculation and the exit width calculation. Even if your floor area could hold 500 people, narrow exits might limit you to 200.

Door Clear Width	Maximum Persons
750mm (minimum)	100
850mm	110
1,050mm	200
Over 1,050mm	200 + 1 per additional 5mm

Key rules

Single exit: capacity capped at 60 persons regardless of door width.
Inward-opening doors: capped at 60 persons unless held open during occupation.
Discount the largest exit: assume it could be blocked. Calculate capacity using only the remaining exits.
Minimum door width: 750mm (900mm where wheelchair users are expected).

What Does “From Time to Time” Mean?

The Act applies to venues where 200 or more people are present “from time to time”. This does not mean your average daily footfall. If your venue regularly hits 200+ on busy nights, during weekend peaks, or at seasonal events, you are likely in scope.

A single unexpected one-off exceedance does not trigger the duty. But repeated peaks (even only on Friday nights or during Christmas) likely do.

Your Venue Is in Scope. What Next?

If the calculator shows you're in the standard tier (200-799), you need public protection procedures for four things: evacuation, invacuation, lockdown, and communication. Your staff and volunteers need to know these procedures.

Read our complete compliance guide for the full picture, or use Standard Tier to generate your PPP, train your staff and volunteers, and build an audit trail in 10 minutes.

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Frequently Asked Questions

How do I measure floor area for the calculator?

Measure the usable floor area in square metres. Exclude stair enclosures, lifts, toilets, corridors, plant rooms, and bar serving areas (behind the bar). Do not exclude counters or display units. If a room has zones with different uses, measure each zone separately.

What if my venue has areas with different uses?

Add each area as a separate zone in the calculator. A pub might have a standing bar area (0.3 m²/person), a restaurant section (1.0 m²/person), and an office (6.0 m²/person). The calculator sums them all.

Why is the largest exit discounted?

Fire safety methodology assumes the largest exit could be blocked by fire (or in this context, a security incident). Your exit-based capacity is calculated using only the remaining exits. This accounts for the possibility of one exit being blocked, rather than assuming every exit will be available.

What if my door opens inward?

Inward-opening doors (opening against the flow of evacuation) are capped at 60 persons unless they are held open during occupation. Tick the 'Opens inward' checkbox for any such exit.

Does capacity include staff?

Yes. Martyn's Law capacity means everyone reasonably expected on site at the same time: customers, staff, volunteers, and contractors. The calculator adds your staff count to the occupancy figure to give the total.

Can I use a different method instead of floor space factors?

Yes. The Act accepts six methods: fire safety occupancy (this calculator), historical attendance data, fixed seating counts, ticket/registration caps, licence restrictions, and any other reasonable evidence. Use the 'Fixed Seating / Known Capacity' option for non-floor-space methods.

What if my venue goes over 200 only occasionally?

The Act uses the phrase 'from time to time'. If your venue regularly reaches 200 or more people (even just on busy nights or during seasonal peaks) you are likely in scope. A single unexpected one-off does not trigger the duty.

Official Sources

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Last reviewed: 3 July 2026. Based on the Terrorism (Protection of Premises) Act 2025, Approved Document B, and Home Office factsheets available at the time of writing. Floor space factors and exit width rules are from fire safety guidance and may not reflect your specific premises conditions.

This guide is general information about the Terrorism (Protection of Premises) Act 2025, not legal advice. Duties under the Act rest on the responsible person for each venue and cannot be transferred. If you're unsure how a specific requirement applies to your premises, take advice from a solicitor or qualified security adviser before acting on anything you read here.

Standard Tier is an independent platform and is not affiliated with the UK Home Office, the SIA, or any government body.