Martyn’s Law capacity calculator
The single thing most venues get wrong about Martyn’s Law is the headcount. It is the number of people you can reasonably expect at the same time— staff included — not your seating plan, your licensed capacity or your fire figure. Put your numbers in and see which side of the 200 and 800 lines you fall.
Last reviewed: June 2026
Enter your numbers above to see an indicative tier. This is a guide, not a verdict on the law — the responsible person makes the final call.
How to count the right number
Martyn’s Law works on two thresholds. Premises where 200 to 799 people may reasonably be expected at the same time fall in the standard tier; 800 or more falls in the enhanced tier. Below 200 at every realistic peak, and the duties most likely do not apply at all. Three things trip people up:
- Staff count too.Bar, kitchen, door, stewards, performers, contractors — everyone in the building at that moment is part of the number. A room that holds 190 customers can be in scope once a full team is added.
- “From time to time” means your peaks, not your average.The test is your busiest predictable occasion — a cup-final night, a sell-out show, the Friday before Christmas — not a quiet Tuesday. If you can foresee those nights, they count, even a handful of times a year.
- It is not your fire or licensed capacity. Those are useful evidence for what your space can hold, but the legal test is what you reasonably expect to be there. Use them to support your figure, not to replace the judgement.
However you reach your number, write down the reasoning — the night you based it on, the door counts or ticketing behind it, the staff on the rota. A dated note that explains how you got there is worth far more than a bare figure, because it shows your working if anyone ever asks. If you land near a threshold, that is exactly where it pays to be careful: a predictable peak that tips you from 190 to 210, or 780 to 810, changes which tier applies.
Want the full picture, not just the number?
The free readiness checker takes the capacity question further — public access, the responsible person, the qualifying-event rules — and gives you an indicative tier with the reasoning and the official guidance it rests on.
What this is — and what it is not
martynslaw.app is a preparation and document-management tool. It is not legal advice, not official guidance, not official certification, not SIA approval and not a guarantee of compliance. The responsible person must review and approve all documents before use.
martynslaw.app is an independent product. It is not affiliated with, or endorsed by, the Home Office, the Security Industry Authority or any other public body. Official sources are cited as sources only.