You have confirmed the venue, sent out the invitations, and now you are standing in the drinks aisle of a wholesaler with absolutely no idea how many bottles to put in the trolley. If you have ever hosted a party at home, in a marquee, or at a hired venue and tried to estimate drinks quantities, you know the quiet dread of getting it badly wrong. Too little and your guests are nursing warm tap water by nine o clock. Too much and you are staring at forty untouched bottles of Sauvignon Blanc for the next six months.
Getting drinks-per-head right is one of the most practical problems in event planning, and it is surprisingly tricky. Guest demographics, event duration, time of year, food service, and even the day of the week all play a role. Here is a realistic framework that takes the guesswork out of it.
The Baseline Formula Most People Get Wrong
The internet is full of advice suggesting one drink per person per hour. It is a tidy number, easy to remember, and consistently underestimates what British adults actually drink at a celebration. In practice, the first hour of any event sees higher consumption as guests arrive, settle nerves, and get into the spirit of things. A more reliable starting point is:
- First hour: 2 drinks per guest
- Each subsequent hour: 1 to 1.5 drinks per guest
For a five-hour evening party with 80 guests, that gives you roughly 400 to 480 drinks. That is a significant difference from the 400 flat that the one-drink-per-hour rule would suggest, and the gap widens with longer events. It also matters what counts as a drink. A 175ml glass of wine, a 330ml bottle of beer, a single-measure spirit and mixer, or a cocktail each count as one unit in this context.
Adjusting for Your Actual Guest List
The baseline is just that. You need to adjust for reality, and your guest list is the single biggest variable.
- Age profile: A crowd of 25 to 40 year olds at a summer birthday will drink more than a mixed-age family christening. If your guest list skews older or includes a lot of children and teenagers, reduce your per-head estimate by 15 to 20 per cent for the adult count alone.
- Day versus evening: A Saturday afternoon garden party that wraps up at six will see noticeably lower consumption than an evening event running until midnight. Daytime events typically come in around 20 per cent below the baseline.
- Food service: A sit-down dinner with courses naturally paces drinking. Standing buffets and canape receptions, where people graze and move around, tend to push consumption slightly higher.
- Season: Summer events see more demand for chilled beer, prosecco, and long cocktails. Winter events lean toward red wine, whisky, and warming serves. Total volume is roughly similar, but the split across categories shifts considerably.
If you know your crowd well, trust your instinct and adjust. If your Uncle Derek and his golf friends are coming, add a case of ale and do not overthink it.
Splitting the Order Across Categories
Assuming a mixed crowd with a free bar or generous host arrangement, a sensible category split looks like this:
- Wine: 40 to 50 per cent of total serves, split roughly 60/40 white to red in summer and 50/50 in winter
- Beer, lager, and cider: 20 to 30 per cent
- Spirits and cocktails: 15 to 20 per cent
- Soft drinks and non-alcoholic options: 10 to 15 per cent (and rising; do not underestimate this category in 2025)
A standard 750ml bottle of wine pours roughly six glasses. A 70cl bottle of spirits yields around 28 single measures. These conversion figures let you translate drink counts into actual bottles, which is what you need when placing an order.
The Hidden Costs of Getting It Wrong
Overordering is not just a storage problem. If you are buying on a sale-or-return basis from a supplier, you need to keep bottles chilled but unopened, which is harder than it sounds when you have volunteer bartenders. If you are not on sale or return, you are simply absorbing the cost. Underordering is worse. Running out of drinks at nine thirty on a Saturday night is the kind of hosting failure people remember, and it creates a scramble to find an off-licence that is still open.
This is precisely why many private hosts find that outsourcing the bar entirely removes the single most stressful logistical element of their event. A professional mobile bar service handles stock estimation, supply, chilling, service, and leftover management. You are not left doing mental arithmetic in a cash and carry the week before your party.
When It Makes Sense to Hand It Over
If your event has more than about 40 guests, runs longer than four hours, or involves cocktails that need preparation, the economics of hiring a mobile bar start to make strong sense. You avoid waste, you avoid the upfront capital outlay of buying full cases across multiple categories, and you get trained staff who pace service and manage the flow of the evening.
For smaller, more informal gatherings where you want to stay hands-on, a self-serve setup like a Bar in a Box can hit the sweet spot. You get pre-selected stock, the equipment, and the glassware delivered, and your guests help themselves. It keeps costs down while still looking polished.
Viva Bar Hire offers both fully staffed mobile bars and their self-serve Bar in a Box across the whole of the UK. If you would rather enjoy your own party than spend it counting bottles behind a trestle table, get in touch at vivabarhire.co.uk for a free quote tailored to your guest numbers, event style, and preferences.