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The working rule is about 1 to 1.5 tablespoons of grounds per cup, and on a percolator a cup means 5 ounces, not 8. That lands close to the SCA Golden Cup target of roughly 55 grams of coffee per liter of water, a ratio in the 1:15 to 1:18 range. Presto's own manual for its 12-cup pot suggests 10 to 16 tablespoons for a full pot, and coffee urn instructions scale the same idea up to 100 cups. Exact per-size numbers are in the tables below.
Why percolator math trips people up
Two things throw off every percolator ratio guess. First, the cup markings inside the pot are 5-ounce cups, so a "12-cup" percolator holds about 60 ounces of brew, not 96. Presto states this plainly in its manual: "One cup is approximately 5 ounces brewed coffee." Second, percolators recirculate water through the grounds over and over, which extracts hard. If you dose a percolator like a drip machine you usually end up over-extracted and bitter, which is why the manufacturer ranges start lower than you might expect and give you room to climb.
So the honest answer is a range, not a single scoop count. Start at the lower end of the manufacturer table, taste, and add a tablespoon at a time on the next pot. Grind matters too: Presto calls for regular or percolator grind, which is coarser than drip, so the water can circulate without choking the basket. A fine grind will slip through the basket holes and cloud the pot.
Percolator coffee ratio by pot size
The first table is the electric percolator range straight from the Presto 12-cup stainless steel coffee maker manual (Form 49-218R). The second is the standard coffee urn measuring guide used across 30 to 100 cup urns like West Bend, measured in standard 8-ounce dry-measure cups of grounds. Both use 5-ounce servings.
Small percolators (2 to 12 cups)
| Cups of brew (5 oz each) | Tablespoons of ground coffee |
|---|---|
| 2 cups | 2 to 3 tbsp |
| 4 cups | 3 to 7 tbsp |
| 6 cups | 5 to 10 tbsp |
| 8 cups | 7 to 13 tbsp |
| 10 cups | 8 to 15 tbsp |
| 12 cups | 10 to 16 tbsp |
Presto notes that 4 tablespoons equals a quarter cup, so a full 12-cup pot at the strong end is about a cup of grounds. Make at least 2 cups at a time or the flavor falls apart.
Large urns (12 to 100 cups)
| Cups of brew (5 oz each) | Ground coffee (8 oz dry-measure cups) |
|---|---|
| 12 to 15 cups | 3/4 cup |
| 20 to 25 cups | 1 1/2 cups |
| 30 to 36 cups | 2 cups |
| 40 to 45 cups | 2 1/2 cups |
| 50 to 55 cups | 3 1/4 cups |
| 60 to 65 cups | 3 3/4 cups |
| 80 to 85 cups | 5 1/2 cups |
| 95 to 100 cups | 6 1/4 cups |
The urn chart is calibrated for mild-strength coffee, which is what most crowds prefer, and every urn manual says the same thing: adjust up or down to taste. If you are brewing for a room that likes it strong, nudge each row up by a quarter cup.
Buying grounds for a big event or a new pot? An automatic percolator or coffee urn on Amazon will have its own measuring guide printed on the basket, but the numbers above are the fallback when the manual is long gone.
Improving your brew? Browse our free coffee tools, print the brew ratio card, and try our method: the descending pour.
Related ratios and guides
- Drip coffee ratio for the everyday auto-drip machine, where the cup is a different size.
- French press ratio if you want a full-immersion brew with a coarser grind.
- Coffee gear guides for the rest of our brewer and grinder breakdowns.
FAQ
How many tablespoons of coffee per cup in a percolator? About 1 to 1.5 tablespoons per 5-ounce cup. Presto's 12-cup manual works out to roughly that once you spread its 10 to 16 tablespoon range across the pot. Start low and climb, since percolators extract hard.
Is a percolator cup 8 ounces? No. The cup markings inside a percolator or urn are 5-ounce cups. Presto and standard urn instructions both define a cup as about 5 ounces of brewed coffee, so a "12-cup" pot yields around 60 ounces.
What grind should I use in a percolator? Regular or percolator grind, which is coarser than drip. A fine grind slips through the basket holes and clouds the pot, and it over-extracts because the water passes through the grounds repeatedly.
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