Somewhere in the last month of planning, a caterer or a liquor store will ask you a question that sounds simple: how much do you want? The answer is arithmetic, and the wedding industry has already done the studies. This guide is the formulas — drinks, food quantities, and dietary counts — with worked examples you can steal. No vibes, no "it depends on your crowd" hand-waving until the very end, where it briefly does.
The master drink formula
The standard consumption model, used by caterers everywhere:
One drink per guest for the first hour, then 0.75 drinks per guest per hour after that. Round up.
For a 120-guest wedding with a 5-hour reception:
- Hour one: 120 drinks
- Hours two through five: 120 × 0.75 × 4 = 360 drinks
- Total: ~480 drinks
Adjust the base rate for your actual crowd: a heavy dancing crowd in July drinks more (use 1.0/hour flat), a brunch reception or an older crowd drinks less (0.5–0.75 after hour one). Guests under 21 and pregnant guests come out of the count entirely — one more reason the guest list, not memory, should feed this number.
Splitting the total: the 40/40/20 rule
For a full bar, the classic split is 40% wine, 40% beer, 20% spirits (shift to 50/30/20 for a wine-forward crowd, or drop the spirits line for beer-and-wine only). Servings per container:
| Container | Servings |
|---|---|
| Wine bottle (750 ml) | 5 glasses |
| Champagne bottle, for toasts | 6 pours |
| Case of beer | 24 |
| Half-barrel keg | ~124 pints |
| Spirits bottle (750 ml) | ~16 cocktails |
Worked example — 480 drinks, standard split:
- Wine: 192 glasses ÷ 5 = ~39 bottles (buy 42; split roughly 60/40 white-to-red for a warm-weather wedding, reverse for winter)
- Beer: 192 servings = 8 cases, or 1.5 kegs
- Spirits: 96 cocktails = ~6 bottles (750 ml) plus mixers
- Champagne toast, if separate: 120 guests ÷ 6 pours = 20 bottles
Add 10% over the computed order — the classic mistake is buying to the average and running the bar dry at 9:40 pm. Most liquor stores take returns on unopened bottles; ask when you order, and over-buying becomes free insurance. And don't forget the unglamorous lines: ice at 1–1.5 lbs per guest, one bartender per 75 guests, and 20–30% more non-alcoholic options than you think you need.
Food quantities, the short version
Catering usually prices per head and handles quantities, but for the pieces couples self-manage:
| Item | Per guest |
|---|---|
| Cocktail-hour appetizers (dinner follows) | 4–6 pieces |
| Appetizers replacing dinner | 12–15 pieces |
| Cake | 1 slice — order for 85% of the count |
| Late-night snack | plan for 60% of guests |
The cake number surprises people: between the dancing crowd and the early leavers, 100% cake coverage produces a week of leftover cake. (There are worse problems.)
Dietary counts: the reconciliation problem
The drink math is easy compared to the question the caterer asks at two weeks out: final count with dietary breakdown. The failure mode is collecting restrictions in four places — RSVP cards, texts, a parent's memory, a spreadsheet column labeled "notes??" — and reconciling them at midnight.
The fix is structural: dietary restrictions are guest-list data, collected at RSVP time, attached to the guest record, and summed by query, not by rereading a text thread. The summary the caterer needs looks like: 94 attending — 4 vegetarian, 2 vegan, 3 gluten-free, 1 severe nut allergy (table 6), 2 kids' meals. The severe-allergy line should carry the table number; that's the difference between a note and a safety protocol. The guest list guide covers collecting this cleanly.
When the guest list moves, the math moves
Every number above has the guest count as its input, and the guest count changes weekly until the RSVP deadline. Run the drink math at 140 invited, and by the time 118 confirm, the order is 15% oversized — real money at wedding markups. The discipline: compute from the projected final count, recompute when it shifts, and place the order at two weeks out when the count freezes. If the math lives in a formula rather than on the back of an envelope, recomputing costs nothing.
How this works in ringbearer
ringbearer's food & drink module runs the consumption model against the live guest list: per-hour ratios by drink type (with overrides for your crowd), bar-style and dinner-style settings, cost estimates, and a dietary summary that aggregates automatically from RSVPs — including the allergy-with-table-number line, since the seating chart lives in the same database. When a guest declines, the bottle count and the vegetarian tally both correct themselves before you've read the text. The product tour is here.
The hand-wave, as promised
The formulas get you to the right order of magnitude; the last 10% is knowing your people. If your families treat an open bar as a competitive event, run the 1.0/hour rate and add a case. If half the list is training for marathons, shift the split toward sparkling water and save the money for the photographer. The math isn't a substitute for judgment — it's what frees your judgment to work on the last 10% instead of the whole guess.
See how this works in the app: the product tour.