# Brew Ratio (/en/docs/foundation/phase-4/chapter-22)



## Phenomenon [#phenomenon]

Every morning you scoop two spoonfuls of coffee and brew a big mug.

Some days it is just right; some days it is clearly too weak. Then you switch to a dark roast, and with the same two scoops it comes out weak almost every day.

You believe you do the same thing every morning. Do you?

## Variables [#variables]

The "amount" in a cup of coffee involves three numbers:

| Number     | What it is                                |
| ---------- | ----------------------------------------- |
| Dose       | How many grams of ground coffee           |
| Brew water | How many grams of water you pour in total |
| Beverage   | How many grams end up in the cup          |

The **brew ratio** is usually written like "1:16": 1 gram of coffee to 16 grams of brew water. Notice the beverage is less than the brew water, because the grounds hold on to some water, which stays behind in the brewer.

A scoop fixes **volume**, not weight.

## Experiment [#experiment]

A thought experiment: same coffee, same grind, same pour-over technique, three cups:

1. 15 g coffee, 250 g water;
2. 15 g coffee, 300 g water;
3. 18 g coffee, 250 g water.

<Predict>
  Rank them from strongest to weakest. Which two will be closest in character — leaning sour or leaning bitter?
</Predict>

One more: with the same spoon, take two scoops of a light roast and two scoops of a dark roast and weigh them.

<Predict>
  Do they weigh the same? If not, which is lighter?
</Predict>

## Observation [#observation]

From strongest to weakest: 18 g with 250 g, then 15 g with 250 g, then 15 g with 300 g.

Changing the ratio changes **strength** the most; the character of the cup usually only shifts slightly — <Claim level="rule-of-thumb">much less than when you change the grind</Claim>. It shifts at all because in a pour-over, more coffee means a deeper bed and slower flow, so extraction changes a little too.

Two scoops of dark roast usually weigh less than two scoops of light roast. <Claim level="established-mechanism">The darker the roast, the more the bean expands and the more water and material it loses, so the same volume weighs less</Claim>. That is why the dark roast at the start was "always weak": you thought you used the same amount, but you used less.

## Model [#model]

### Where strength comes from [#where-strength-comes-from]

Borrow two ideas the next chapter covers in depth: **extraction** is how much of the grounds the water took away, and **extraction yield** is that amount as a share of the dose; **strength** is how concentrated the cup is. They are related simply:

**Dissolved coffee in the cup = dose × extraction yield**

**Strength = dissolved coffee in the cup ÷ beverage**

So there are two ways to make a cup stronger:

* **More coffee, or less water** — changes the ratio; the character barely moves;
* **More extraction** — strength rises a bit, but the flavor moves toward bitter and drying.

The ratio is the main dial for strength. Extraction is a secondary dial, and it drags the flavor along with it.

### Adding water after brewing is not the same as brewing with more water [#adding-water-after-brewing-is-not-the-same-as-brewing-with-more-water]

Adding hot water to the cup after brewing changes only strength; extraction is untouched — what was taken from the grounds, and in what proportions, stays the same. Chapter 23 lets you taste this for yourself.

Brewing with more water is different: more fresh water passes through the bed, and <Claim level="established-mechanism">the less dissolved material water already holds, the more it can keep dissolving</Claim>, so extraction rises a little. To make the same cup a bit weaker, diluting afterwards is usually more predictable than changing the brew water.

### The water the grounds keep [#the-water-the-grounds-keep]

Coffee grounds hold on to some water — <Claim level="rule-of-thumb">roughly twice their own weight</Claim>. With 15 g of coffee and 250 g of water, only about 220 g ends up in the cup. When converting someone else's recipe, check whether they mean brew water or beverage.

### "Just right" strength is a preference [#just-right-strength-is-a-preference]

<Claim level="common-practice">Most common pour-over recipes fall between 1:15 and 1:17</Claim>, which is a useful starting point. But how strong is right? <Claim level="preference">Research found this is where people disagree the most</Claim>. Strength has no right answer — only what you like.

## Transfer [#transfer]

Write recipes as "dose + ratio", not "two scoops". Then scaling for a different mug or more people is simple multiplication.

| What you taste            | One adjustment to make first                                                |
| ------------------------- | --------------------------------------------------------------------------- |
| Balanced, just too weak   | Use a little more coffee, change nothing else                               |
| Balanced, just too strong | Add some hot water after brewing                                            |
| Weak and sour             | Leave the ratio alone; extraction may be low — Chapter 23 shows how to tell |
| A new bag tastes weaker   | Weigh it first: the same number of scoops may weigh less                    |

A kitchen scale that reads to one gram is the best-value tool in this chapter.

## Misconceptions [#misconceptions]

**"Strong means well extracted."** Strength is set mainly by the ratio. An intense, sour cup may well be under-extracted.

**"There is a standard ratio."** Common ratios are starting points. Strength is the most personal variable of all.

**"Scoops are accurate enough."** A scoop measures volume. Different roasts and grinds put different weights in the same scoop.

## Real Lab [#real-lab]

<RealLab id="lab-ratio" />

One way to do it: fix the dose, say 15 g, and brew three cups at 1:14, 1:16 and 1:18 with the same grind and technique. When tasting, first rank them by strength, then ask: apart from strength, how different is their character?

## Check Your Model [#check-your-model]

**Predict.** You double both the dose and the water and brew one big batch in the same dripper. What happens to strength? Does anything else change?

<Accordions>
  <Accordion title="One way to think about it · Predict">
    The ratio is unchanged, so strength is roughly the same. But the bed is deeper: water passes through more coffee, flows more slowly and stays in contact longer, so extraction may rise a little and the cup lean slightly bitter. If it leans noticeably, grind a little coarser to compensate.
  </Accordion>
</Accordions>

**Diagnose.** A cup is balanced but too strong. A friend suggests grinding coarser. Why is that not the best first step?

<Accordions>
  <Accordion title="One way to think about it · Diagnose">
    A balanced flavor means extraction is fine; the problem is strength. Grinding coarser changes extraction, moving the flavor toward sour and thin, while strength drops only a little. It is more direct to add some hot water after brewing, or use a bit less coffee next time.
  </Accordion>
</Accordions>

**Explain.** In your own words: why can two cups be equally strong yet taste completely different?

<Accordions>
  <Accordion title="One way to think about it · Explain">
    Strength only tells you how much is dissolved, not what was dissolved. One cup might use more coffee extracted less, the other less coffee extracted more, and both end up equally strong. The first leans sour, the second bitter.
  </Accordion>
</Accordions>