How to Scale a Coffee Recipe: From One Cup to a Crowd
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Your one-mug recipe is perfect. Now twenty people are coming for brunch. The good news: scaling coffee is just ratio math. Keep the same coffee-to-water ratio, multiply by the volume you need, and add a little for water the grounds soak up. So how much coffee for a crowd? As a quick rule, for 20 guests drinking about one and a half 8 oz cups each, plan on roughly 440 g (just under 1 lb) of ground coffee and 8 liters (about 2.1 gallons) of water.
Below you will find the method, a table for 10 to 50 people, cold brew concentrate math, how much to buy and how to keep a big batch tasting good.
Key takeaways
- Scale by ratio, not by scoops: grams of coffee = liters of water × your ratio (for example 55 g per liter).
- Grounds hold back water, about twice their weight, so brew roughly 12% more water than the coffee you want to serve.
- Plan on about 1.5 cups (8 oz each) per coffee drinker for a morning event; adjust for your crowd.
- Cold brew concentrate at 1:5 needs much more coffee per drink, but it is diluted before serving.
- Keep brewed coffee in a preheated thermal carafe instead of on a hot plate.
In this article
- The ratio method
- Coffee for 10 to 50 people
- Batch brewing: practical setups
- Cold brew concentrate for a crowd
- How much coffee to buy
- Keeping coffee hot and tasty
- FAQ
The ratio method
Every coffee recipe is a ratio of coffee to water. The National Coffee Association’s “golden ratio” is 1 to 2 tablespoons of ground coffee per 6 oz of water, and the Specialty Coffee Association’s reference strength is 55 g of coffee per liter of water. Because tablespoons vary, weigh when you scale.
Step 1: Find your scale factor
Scale factor = new water amount ÷ original water amount
Example: your pour-over uses 30 g of coffee and 500 g of water. You want 1,500 g of water. Scale factor = 1,500 ÷ 500 = 3, so you need 30 × 3 = 90 g of coffee.
Step 2: Account for absorption
Spent grounds keep roughly twice their dry weight in water. If you brew with water W and coffee C, you serve about W − 2C. At 55 g per liter, that means you get back about 89% of the water you pour. So:
Water to brew = drink volume you want ÷ 0.89
Step 3: Keep strength, not time, constant
Bigger batches in bigger brewers can extract differently. If the big batch tastes weak, grind slightly finer or nudge the ratio toward 60 g per liter; if it tastes harsh, go a little coarser.
Coffee for 10 to 50 people
Assumptions: 1.5 servings of 8 oz (237 ml) per person, brewed at 55 g of coffee per liter of water, with grounds holding back about twice their weight in water. Values are rounded.
| People | Servings (8 oz) | Coffee to serve | Water to brew | Ground coffee |
|---|---|---|---|---|
| 10 | 15 | 0.94 gal (3.6 l) | 1.05 gal (4.0 l) | 220 g (0.48 lb) |
| 20 | 30 | 1.87 gal (7.1 l) | 2.11 gal (8.0 l) | 440 g (0.97 lb) |
| 30 | 45 | 2.81 gal (10.6 l) | 3.16 gal (12.0 l) | 660 g (1.45 lb) |
| 40 | 60 | 3.75 gal (14.2 l) | 4.21 gal (15.9 l) | 880 g (1.93 lb) |
| 50 | 75 | 4.69 gal (17.7 l) | 5.27 gal (19.9 l) | 1,100 g (2.42 lb) |
Quick rule from the table: about 22 g of coffee per person for 1.5 cups each. For a long event, or a crowd of serious coffee drinkers, plan on 2 cups each and multiply the coffee by 4/3.
Adjusting for your crowd
- Afternoon event or dessert: many guests take one cup or skip coffee; 1 serving per person is often enough.
- Morning meeting or brunch: 1.5 to 2 servings per person.
- Mixed crowd: offer a smaller pot of decaf, often about a quarter to a third of the total, depending on the time of day.
Batch brewing: practical setups
| Setup | Batch size | Good for | Tip |
|---|---|---|---|
| 12-cup drip machine | Many hold about 60 oz (1.8 l) of water: use about 98 g of coffee for roughly 53 oz brewed | Up to 10–12 people, brewed in rounds | Brew a fresh pot every 30–45 minutes rather than one giant early batch |
| Two machines side by side | Double | 20–25 people | One regular, one decaf |
| Large French press or several presses | 1–1.5 l each | Small gatherings | Decant right after pressing so it does not keep extracting |
| Rented coffee urn | Large | 30–50+ people | Follow the urn’s markings, but check strength with the ratio method |
The “cups” on a coffee maker are usually smaller than a mug, often 5 or 6 oz, so check your machine’s capacity in ounces or liters before you calculate.
Cold brew concentrate for a crowd
The National Coffee Association gives a cold brew ratio of 1 g of coffee to 4–5 g of water, steeped for around 12 hours. That makes a concentrate meant to be diluted. Here is the math with a 1:5 ratio and a typical 1:1 dilution (4 oz concentrate plus 4 oz water or milk per 8 oz drink).
Concentrate yield = water − (2 × coffee). With coffee = water ÷ 5, you keep about 60% of the water you started with.
| Guests (one 8 oz drink each) | Concentrate needed | Water to steep | Coarse ground coffee |
|---|---|---|---|
| 10 | 40 oz (1.2 l) | About 8 1/3 cups (2.0 l) | 390 g (0.87 lb) |
| 20 | 80 oz (2.4 l) | About 16 2/3 cups (3.9 l) | 790 g (1.74 lb) |
| 30 | 120 oz (3.5 l) | 25 cups (5.9 l) | 1,180 g (2.61 lb) |
| 50 | 200 oz (5.9 l) | About 41 2/3 cups (9.9 l) | 1,970 g (4.35 lb) |
Dilution math
- 1:1 (concentrate:water or milk) halves the strength: 4 oz + 4 oz.
- 1:2 makes it a third as strong as the concentrate: about 2.7 oz + 5.3 oz for an 8 oz drink, so the same concentrate serves 50% more drinks.
- Ice also dilutes as it melts, so start stronger than you think and let guests add water or milk.
Cold brew has a big hosting advantage: you make it the day before and nothing needs to stay hot. Keep it in the fridge until serving.
How much coffee to buy
Take the coffee weight from the tables, add about 10% for spills, a stronger pot or a second round, and round up to bag sizes.
| Event | Coffee needed (+10%) | What to buy |
|---|---|---|
| 10 people, hot coffee | About 0.53 lb (240 g) | One 12 oz bag |
| 20 people, hot coffee | About 1.07 lb (485 g) | Two 12 oz bags (1.5 lb), or one 1 lb bag if you skip the buffer |
| 50 people, hot coffee | About 2.66 lb (1.2 kg) | A 2 lb bag plus a 12 oz bag, or a 5 lb bag if you will use the rest |
| 20 people, cold brew | About 1.9 lb (870 g) | A 2 lb bag |
Keeping coffee hot and tasty
- Use thermal carafes or airpots. Preheat them with hot water for a few minutes, empty, then fill with fresh coffee.
- Avoid long stays on a hot plate. Continuous heating makes coffee taste flat and bitter. Move it to a carafe as soon as it is brewed.
- Brew in waves. For long events, brew a new batch every 30–45 minutes instead of everything at once.
- Label clearly. Regular, decaf and any flavored option should be obvious at a glance.
- Grind just before brewing if you can, or buy freshly ground coffee in the grind your brewer needs.
- Set up a milk station. Milk, a plant milk, sugar and stirrers next to the coffee keep the line moving.
Coffee for your event
For a crowd-pleasing hot batch, our House Blend is a smooth, clean medium roast of Central and South American coffees with nutty, sweet chocolate and mild citrus notes, available in sizes from 12 oz up to 5 lb. For cold brew, our Cold Brew Coffee is a dark French roast blend ground very coarse specifically for cold brew, 100% coffee with nothing artificial. Every bag is roasted 1–5 days before delivery, so order a few days before your event and it arrives fresh.
How much coffee for a crowd FAQ
How much coffee do I need for 20 people?
About 440 g (just under 1 lb) of ground coffee brewed with 8 liters (2.1 gallons) of water gives 30 cups of 8 oz, enough for 1.5 cups each. Buy about 1.1 lb to have a buffer.
How much coffee for 50 people?
About 1.1 kg (2.4 lb) of coffee and 20 liters (5.3 gallons) of water for 1.5 cups each. Buy around 2.7 lb.
How do I scale a coffee recipe?
Divide the new water amount by the original water amount to get a scale factor, then multiply the coffee by that factor. Keep the ratio the same and weigh rather than scoop.
How do I dilute cold brew concentrate?
Start with 1 part concentrate to 1 part water or milk, then adjust. A 1:2 dilution makes a lighter drink and stretches the concentrate further.
How long can brewed coffee sit out?
Flavor drops quickly on a hot plate. In a preheated thermal carafe it stays pleasant much longer; for the best taste, brew fresh batches during the event.
Sources
- National Coffee Association USA, “Drip coffee” brewing guide (golden ratio). Link
- National Coffee Association USA, “Cold brew” guide (1:4 to 1:5 ratio). Link
- Specialty Coffee Association of America, “Golden Cup Standard” (55 g/L). PDF
- NIST, unit conversions (1 US fluid ounce = 29.5735 ml; 1 lb = 453.592 g). Link
Facts checked in October 2026.
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