The rules of thumb behind the numbers
Caterers and venues use simple per-guest rules to estimate quantities, and this calculator uses the same kind of rules. They are sensible starting points, not guarantees. A crowd of rugby players and a family lunch with lots of children will eat and drink very differently, so adjust the non-drinker percentage and the buffer to suit your guests.
- Canapés. About 4 per guest for a one-hour drinks reception before a meal, plus 2 more for each extra hour. If canapés replace a meal, allow about 6 in the first hour and 4 for each hour after.
- Finger buffet. About 10 items per guest when it is the main meal.
- Evening food. Not everyone eats at the evening buffet, so the calculator allows portions for about three quarters of evening guests.
- Fizz. A 75cl bottle pours 6 flutes of 125ml. The calculator allows 2 glasses per drinker for the reception and 1 for the toast.
- Wine with the meal. About half a bottle per drinking guest, with 5 glasses of 150ml per bottle.
- Evening bar. Roughly one drink per drinking guest per hour, split about 60% beer or cider and 40% wine.
- Soft drinks, water and ice. Non-drinkers get a soft drink (330ml) every two hours, everyone gets some mixers and water, and ice is 0.5kg per guest, doubled in hot weather.
Why a buffer matters
Running out of drinks is far more noticeable than having a few bottles left over. The default 10% buffer covers heavier drinkers, spillage and extra guests. Many UK wine merchants and supermarkets offer sale-or-return on unopened bottles for events, which lets you buy generously and return what you do not use. Ask before you order, and keep the boxes intact.
Plan for dietary needs and allergens
Quantity is only part of catering. UK food businesses must tell customers if any of the 14 major allergens are in the food they serve, including celery, cereals containing gluten, crustaceans, eggs, fish, lupin, milk, molluscs, mustard, tree nuts, peanuts, sesame, soya and sulphites. Collect dietary requirements with your RSVPs and pass a clear list to your caterer with your final numbers, usually two to four weeks before the event.
Bringing your own drinks?
If your venue charges corkage, add it to the cost of each bottle before deciding whether bringing your own is cheaper. Check too whether the venue's licence allows you to supply alcohol, and who will serve it.