Fixes

Seven ratio mistakes almost everyone makes

Nov 16, 2026 · ~7 min read · Last verified: 2026-11-16

Most bad cups aren't bad luck — they're one of seven arithmetic or measurement errors that repeat quietly every morning. We collected them from our own brewing logs and from the gaps between what official recipes say and what people actually do. Each one below has a symptom, a cause, and a one-line fix.

Key takeaways

Bloom water is part of the total; "cups" in recipes are 5–6 oz, not mugs; and a scoop is not a dose.
Changing multiple variables at once destroys your ability to learn from any of them.
Stale beans and wrong water mimic ratio problems — check them before tightening the recipe.
Every fix below ends with "weigh it" — which is why the calculator exists.

1. Counting the bloom as extra water

Symptom: pour-overs that finish fast and taste strong-ish but thin. Cause: pouring a 60–70 g bloom and then pouring the recipe's full 500 g on top — you brewed a 1:11.5 "recipe" with the kinetics of a 1:15. The bloom is the first installment of the total water (Fellow's guide and Blue Bottle's schedule both budget it that way; see the V60 guide). Fix: zero the scale after dosing, pour the bloom, and bring the same counter to the recipe's total — never more.

2. Treating your mug as a "cup"

Symptom: "This ratio is weak" even though you followed it. Cause: brewing standards and older recipes count a cup as roughly 5–6 fl oz (150–180 ml), and moka "cups" are tiny demitasse serves; your 12 oz mug is two to three of those. The fix isn't memorizing cup conventions — it's never using cups at all. Fix: brew by total water weight; when a recipe says "cups," convert with a calculator that states its millilitres-per-cup assumption out loud.

3. Scooping without weighing

Symptom: the same recipe tastes different with every new bag. Cause: bean density swings a scoop by grams — darker roasts are lighter per spoonful, dense light roasts heavier — so your "two scoops" changes dose invisibly with each coffee (the full math is in scale vs scoop). Fix: weigh the dose to the half gram; if you must use a scoop, weigh it once per bag and write the grams on it.

4. Chasing strength when the problem is extraction

Symptom: cup is sour, you add coffee, cup is now sour and muddy. Cause: sourness signals under-extraction (water not pulling enough out of the grounds), and more coffee makes the problem worse, not better — the water has even more to under-extract. Fix: grind finer first, extend time second, touch the ratio last. The decision tree lives in ratio by strength, and the chemistry in grind vs extraction.

5. Changing three things at once

Symptom: occasional great cups you cannot reproduce. Cause: a better cup from simultaneously adjusting grind, ratio and temperature teaches you nothing about which change mattered. Fix: one variable per batch, ideally per day, with notes. It feels slow for a week and then permanently stops the "it was good last Tuesday" problem.

6. Blaming the recipe for stale beans or bad water

Symptom: flat, papery, boring coffee at every ratio. Cause: coffee staling loses the aromatics no ratio can restore, and municipal water issues (chlorine, extreme hardness, high alkalinity) mute or warp flavor across all recipes. Fix: run the diagnostic order — ratio, grind, temperature, then beans, then water (the SCA water targets are in water quality basics). Beans from a bag opened a month ago that's been sitting open: that's a beans problem, and it's the most common "my recipe stopped working" cause of all.

7. Comparing cold-brew concentrate ratios to brewed-coffee ratios

Symptom: "Cold brew is 1:5?! It must be rocket fuel." Cause: the 1:5 (Toddy's instruction sheet) is a concentrate ratio, diluted 1:2 to 1:3 at serving — which lands the drinking strength back around 1:15–1:20, right in filter territory (see the cold brew guide). Fix: always ask whether a ratio describes the brew or the cup; they're the same number for hot methods and stacked numbers for concentrates.

The pattern behind all seven

Every mistake above is an unmeasured assumption: assumed bloom accounting, assumed cup size, assumed scoop mass, assumed cause of sourness, assumed variable attribution, assumed freshness, assumed ratio context. The recipe side of the fix is always the same — weigh, compute, write down, change one thing. That's the entire method behind CoffeeRatio: our calculator fixes the arithmetic, the ratio reference and grind chart fix the targets, and your notes fix the rest.

A note on attribution

Specific numbers in this article (bloom rules, Toddy's 1:5, cup-size conventions) are attributed to their official sources inline and on the linked pages, verified 2026-11-16. The mistakes themselves are universal brewing experience and need no citation — you've probably made at least three of them.