Caterers all use the same formula, and it is worth knowing because it is simple and it holds up: two drinks in the first hour, one per hour after. Written as arithmetic, that is drinks = guests × (hours + 1).
Why two in the first hour
People arrive thirsty and drink socially while the room fills. Consumption is front-loaded and then settles. A five-hour reception works out at six drinks per guest — not because anyone drinks steadily for five hours, but because the first hour does double duty.
| Party | Formula | Total drinks |
|---|---|---|
| 20 guests, 3 hours | 20 × 4 | 80 |
| 50 guests, 4 hours | 50 × 5 | 250 |
| 100 guests, 4 hours | 100 × 5 | 500 |
| 100 guests, 5 hours | 100 × 6 | 600 |
But those aren't all cocktails
This is the step most people skip. At a full bar, guests spread across categories. The two conventions you will see are:
- 50% wine / 25% beer / 25% spirits — the wedding and reception default
- 40% beer / 30% wine / 30% spirits — more typical of general events and casual parties
So of those 500 drinks at a 100-person party, roughly 125–150 are cocktails. If you stock for 500 cocktails you will be drinking gin for a year.
The exception is a single-signature-cocktail party, where the share goes to 100% because there is nothing else to choose. That format is far easier to stock and much faster to serve, which is why experienced hosts keep choosing it.
How many cocktails from a bottle
A 750 ml bottle holds 25.4 fl oz. Everything follows from your pour:
| Pour | 750 ml bottle | 1 L bottle | 1.75 L handle |
|---|---|---|---|
| 1.5 oz / 44 ml (single shot) | 16–17 | 22 | 39 |
| 2 oz / 60 ml (cocktail standard) | 12 | 16 | 30 |
| 2.5 oz / 75 ml (strong) | 10 | 13 | 23 |
That 12-versus-17 gap is the reason published bar-stocking guides contradict each other so often. They are not disagreeing about the maths — they are quietly assuming different pours and not telling you which. If a guide does not state its pour size, its bottle counts are unusable.
One more thing people miss: if a recipe uses two spirits — a Negroni, a Manhattan with vermouth — it draws down two bottles at once. Count it against both.
The two things everyone underbuys
Mixers. Budget about 1 litre per 8–10 mixed drinks. That works out to roughly 1.25–2 litres of tonic, soda or juice for every 750 ml bottle of spirit. Sounds like a lot; it goes fast.
Ice. 1.5 lb (0.7 kg) per guest, or 2 lb in warm weather or at a cocktail-led bar. Ice is the single most common thing to run out of and by far the most annoying to fix at 9pm. It does two jobs — going in glasses and chilling bottles — and people only plan for the first.
Garnish and glassware
- Citrus: published guidance ranges from a quarter to half a lemon and lime per guest. Half is generous; a quarter each is usually enough unless you are serving a lot of gin and tonics.
- Olives, cherries, onions: about two each per guest if you are serving the cocktails that need them.
- Glasses: 1.5 per guest. People set drinks down and lose them.
Don't forget the people not drinking
Plan one non-alcoholic serving per guest per hour regardless of what else you pour, plus 12–16 oz of water per guest per hour. Roughly a third of a typical guest list will want these at some point in the evening, and the standard sources handle it as a flat add-on rather than as a share of guests — which means it is additional to your alcohol count, not carved out of it. The non-alcoholic guide has the detail.
What to batch
Spirits, juices and syrups batch well and can be mixed a day ahead — the flavours actually marry. Anything carbonated does not, at all. Mix the spirit base, chill it, and add soda or sparkling wine only as you pour. The batch cocktails guide covers dilution and storage times.
The cocktail calculator takes your guest count, party length, pour size and bar style and returns bottles, mixers, ice and garnish.