👥 Volunteer Shift Coverage Calculator

Enter your expected attendance and target ratio (like 1 volunteer per 20 attendees) to see how many volunteers you need to cover a shift or event.

Expected attendees

Attendees per volunteer

Number of shifts

How the headcount is worked out

The per-shift figure is your ratio applied to the crowd, rounded up, repeated across the shifts you are staffing:

per shift   = ceiling(attendees / attendees per volunteer)
total slots = per shift × number of shifts

150 attendees at one volunteer per 20 is 7.5, which rounds to 8 on the shift - a part-person cannot cover a door. Split the day into 3 shifts and you need 24 slots filled, not 8. Tighten the ratio to 1 per 15 and the same crowd needs 10 per shift, or 30 slots.

Reading the inputs the way the tool means them

Attendees means people present during one shift, not everyone who passes through all day. If 150 people arrive across three shifts, the crowd at any moment is nearer 50 - entering 150 with 3 shifts would staff for 450.
Slots are not people. Someone taking the morning and the afternoon fills two of the 24. Divide by the shifts a typical volunteer takes to get the number of humans to recruit.
Fixed roles do not scale with the crowd. Check-in, first aid and a floating lead are needed whether 40 or 400 turn up. Work out coverage here, then add those posts on top.

The ratio is yours to choose, except where it is not. Supervising children or vulnerable adults often carries ratios set by licensing rules, your insurer or the venue, and those override any calculator. Check before you publish a rota.

Frequently asked questions

How many volunteers do I need for an event with 150 people?

At a common one-to-twenty ratio, 8 on the floor at any time. Tighter supervision or lots of stations pushes that up; a seated talk with one entrance needs far fewer. Add your fixed roles separately.

Why does the total go up when I add shifts?

Because each shift needs its own full crew. Three shifts of 8 is 24 slots. That is positions to fill, not 24 separate people, if some volunteers stay for two.

How many spare volunteers should I recruit for no-shows?

Ten to twenty per cent above your slot count is the usual habit, and more for an early start on a cold morning. After two or three events you will have your own no-show rate, which beats any rule of thumb.