How Many Portable Toilets Do You Need? A Ratio Guide for Sites & Events
Whether you’re running a construction site or planning an outdoor event, “how many portable toilets do we actually need?” is a question with real consequences. Too few and you’ve got queues, complaints and — on a site — a compliance problem; too many and you’re paying for units nobody uses. Here’s a practical guide to getting the numbers right for both situations.
Construction Sites: It’s a Legal Minimum, Not a Guess
On a construction site, toilet provision isn’t a matter of preference — it’s required under CDM 2015, which mandates “suitable and sufficient” sanitary facilities for the workforce. While the regulations don’t fix a rigid ratio, the widely used industry rule of thumb is:
- 1 toilet per 7–10 workers as a baseline
- Plus adequate washing facilities (hot and cold water) immediately available — a toilet without proper handwashing isn’t compliant
- Scaled up for larger or longer sites, and adjusted for the nature of the work
For most sites, this is covered most easily by a welfare unit (which includes a toilet, washing and rest facilities in one self-contained cabin — see our welfare unit hire guide), with additional standalone portable toilets added as the crew grows. A small site might need a single welfare unit; a larger one, a welfare unit plus several extra toilets.
Remember the facilities must be in place before work starts and kept serviced throughout — provision that’s present but filthy still fails the “kept clean” requirement.
Events: Ratios Depend on Duration, Alcohol and Gender Split
Events are a different calculation, driven by crowd size, how long people are there, and whether alcohol is served (it increases usage significantly). Widely referenced event guidance suggests, as a starting point for events with alcohol running several hours:
- 1 toilet per ~75–100 attendees for events up to around 6 hours
- More units for longer events — usage rises with duration
- Fewer needed if no alcohol is served — non-alcohol events can often work to a lighter ratio
Other factors that push the numbers up:
- Gender split — provision should reflect the expected audience; female and mixed provision often needs more units due to longer usage times
- Accessibility — you must provide accessible toilets for disabled attendees
- Handwashing — wash stations or basins alongside the toilets, especially where food is served
- Event type — a family festival, a music event and a corporate open day all behave differently
Local authority licensing conditions often specify minimum provision for events, so check what your licence requires — it may set the floor.
A Quick Reference
| Setting | Rough starting ratio |
|---|---|
| Construction site | 1 toilet per 7–10 workers (+ washing) |
| Event with alcohol (up to 6 hrs) | 1 per ~75–100 attendees |
| Event, no alcohol | Lighter — fewer units per head |
| Longer events | Increase provision with duration |
Treat these as starting points, not final answers — the specifics of your site or event can move the numbers either way.
Don’t Forget Servicing
For anything beyond a very short event, toilets need servicing — emptying and restocking — to stay usable. A multi-day site or event with unserviced units quickly becomes unpleasant and, on a construction site, non-compliant. Factor servicing into your plan, and use a supplier who includes it.
Other Things Worth Providing
- Wash stations — increasingly expected, essential where food is involved
- Accessible units — a requirement, not an optional extra
- Lighting — for evening events or winter site work
- Urinal blocks — an efficient way to add capacity for larger male-heavy crowds
Get the Numbers Right First Time
Rather than guessing and hoping, tell a supplier your worker numbers or expected attendance and let them spec provision that meets the guidance. Select A Skip provides portable toilets, welfare units and site equipment nationwide, with servicing arranged — so whether it’s a construction site or an event, you get sufficient, serviced facilities without over-ordering.
Planning a site or event? Get in touch with your numbers and we’ll work out what you need — we reply the same working day.
Ratios given are general industry starting points, not statutory figures. Check HSE guidance for sites and your local authority’s licensing conditions for events.