Coffee for a Crowd Calculator
Find out how much ground coffee and water to brew for a group, and how many large urns or pots it takes to serve everyone.
How it works
Water oz = people × cups × cup oz · Ground = water ÷ 6 oz × tbsp-per-6oz · Urns = total oz ÷ (rated cups × 5 oz)
Coffee for a crowd is really two numbers: how much brewed volume you need, and how much ground coffee that volume takes. Volume is people times cups per head times cup size. Grounds follow the classic ratio of about two tablespoons per six ounces of water for standard strength, dialed down for mild or up for strong. Note that coffee-urn ratings use a 5-ounce "cup," so a 100-cup urn actually holds about 500 ounces — plan urns off ounces, not mug counts.
Worked example
30 people at 1.5 cups of 8 oz each need 360 oz of coffee. At 2 tbsp per 6 oz that is (360÷6)×2 = 120 tbsp ≈ 636 g, about 1.40 lb of grounds, with 360 ÷ 128 = 2.8 gallons of water. A 100-cup urn holds 500 oz, so one urn covers it.
Frequently asked questions
Why is a 100-cup urn not 100 mugs?
Percolator urns are rated using a 5-ounce "cup," an old coffee-industry standard. A 100-cup urn holds about 500 ounces, which is closer to 40–60 real 8–12 oz mugs. Always plan capacity in ounces to avoid under-buying.
How much ground coffee per cup?
The common ratio is about two tablespoons (roughly 10 g) per six ounces of water for standard strength. Use 1.5 tablespoons for mild or 2.5 for strong. Adjust to taste — grind, freshness and brewer all shift the result.
Should I also plan decaf?
For groups, a rough 3:1 regular-to-decaf split works well, and decaf is essential later in the day or at evening events. Brew decaf in a clearly labeled second pot or urn.
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This calculator is for educational purposes. Double-check important results before acting on them.