Morning crowds average 1.25 cups each; evening far less.
What you need
| Amount |
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The golden ratio, scaled up
Specialty coffee's standard is 60 g of grounds per litre of water — the "golden ratio." A serving cup at events is 180 ml (6 oz, smaller than a mug, correct for urns), so each cup needs about 11 g of coffee. The calculator multiplies through, then sizes the urn: brew capacity should exceed demand by ~20% because urns can't be refilled mid-service without a gap. Full worked numbers for 20, 50 and 100 people are in the coffee for a crowd guide.
How much coffee for 50 people?
Morning event: 50 × 1.25 = 63 cups ≈ 11.3 L of brewed coffee ≈ 680 g of grounds (a 750 g bag with a little spare). That's a 12-litre urn or two 6-litre brews.
How much milk and sugar?
About half of drinkers take milk (30 ml each) and a third take sugar (one 4 g packet). The calculator includes both, plus 10% decaf if you select morning or afternoon.
Tea drinkers?
Plan 1 tea bag per 5 guests at a coffee-led event — more in the UK and Australia, where it's closer to 1 per 3. Hot water comes from the same urn math.