How much alcohol? The formula, explained
Every number on this site comes from one formula. Here it is, with every assumption on the table, so you can adjust it with your eyes open.
The formula
Total drinks = guests × hours × drinks per hour × crowd modifier × (1 − non-drinker share) × 1.10
| Input | Default | Why |
|---|---|---|
| Drinks per hour | 1.0 | The catering industry's standard planning rate per drinking guest |
| Crowd modifier | Light 0.8 · Average 1.0 · Lively 1.25 | You know your people better than any formula |
| Non-drinker share | 15% | Kids, drivers, anyone skipping — they still need soft drinks |
| Buffer | ×1.10 | Spills, over-pours and the last table still dancing |
The split
Full bar: 35% beer / 35% wine / 30% spirits — the split most caterers start from. Beer & wine only: 50/50. Wine only: 100%. If your crowd is famously beer-first, shift 10 points from wine to beer; the totals matter more than the exact split.
The conversions
| Item | Yield |
|---|---|
| Wine, 750 ml | 5 glasses (5 oz pour) |
| Spirits, 750 ml | ~17 drinks (1.5 oz pour) |
| Beer | 1 can/bottle = 1 drink; 24 per case; ~165 per half-barrel keg |
| Champagne, 750 ml | 6 toast glasses (4 oz pour) |
| Soft drinks | 1.5 servings per non-drinker per hour |
| Ice | ~1 lb per guest |
The honest limits
This is a purchasing estimate built on averages. It does not know that your college friends are in town, that it is a cash bar, or that half the room leaves after dinner. Use the crowd modifier and drinks-per-hour inputs to bend it toward your reality, keep water and food in front of people all night, and give your venue or caterer the final call.
Ready to run it? Open the wedding drink calculator.
Frequently asked questions
Where does 'one drink per guest per hour' come from?
It is the long-standing catering and event-planning rule of thumb: on average, a drinking guest consumes about one standard drink per hour across an event. Individuals vary widely — the rule plans the stock, not any person's consumption.
Why a 10% buffer?
Spills, over-pours, the extra bottle opened 'just in case', and guests who stay to the very end. Ten percent covers normal waste without buying a second wedding's worth of stock — especially when unopened items can be returned.