The two dials that fix most bad cups
Grind and ratio
A coffee bed is a record of how water met ground coffee. Grind size controls the exposed surface and the spaces between particles. Ratio controls how much dry coffee is given to the water. These choices do not act alone, because the brewing method determines how water moves through the bed and how evenly it collects dissolved material.
The useful starting point is measurement rather than appearance. The SCA brewed-coffee window places strength at 1.15-1.35 percent dissolved solids and extraction yield at 18-22 percent of the dry coffee mass. The published ratio is 55 g of coffee per litre of water, plus or minus 10 percent. Those figures describe targets, not a substitute for tasting.
A consistent grind makes adjustments easier to read. A burr grinder generally produces a narrower particle spread than a blade grinder, while a scale makes the coffee-to-water relationship visible. The grind reference table gives practical points from coarse through very fine. Use it as a starting map, then change one variable at a time so the result has a clear explanation.
What grind size actually changes
Grind size changes the area available for water to contact. Finer particles present more exposed surface, so water can dissolve material from them more readily. Coarser particles leave larger spaces and expose less surface. The effect is also tied to flow: a fine bed can restrict movement, while a coarse bed can let water pass with less contact. Method and agitation decide how strongly this difference appears.
The table's descriptions are useful physical anchors. Coarse resembles rough sea salt and suits cold brew or French press. Medium sits around sand and fits cone pour-over or batch drip. Fine is closer to caster sugar and belongs at the espresso end, with moka pot at the finer end. Very fine resembles powder and is associated with Turkish coffee. These labels are reference points, not universal dial positions.
Burr against blade
A burr grinder breaks coffee between two surfaces, making a more controlled distribution of particle sizes. That consistency matters because a bed containing many sizes gives water several different paths and surfaces to work on. A blade grinder chops unevenly, leaving a broad mix that includes dust and larger pieces. The table describes this as a mix of dust and boulders, which makes a single grind setting less meaningful.
Consistency does not mean every burr setting suits every method. It means a change toward coarse or fine is easier to reproduce and evaluate. Start near the table's method reference, keep the ratio steady, and observe the cup. If the result needs correction, change the grind direction rather than changing several inputs at once. A blade grinder can still produce coffee, but its particle mix makes diagnosis less precise.
| Setting | Feels like | Usual method |
|---|---|---|
| Coarse | rough sea salt | cold brew, French press |
| Medium-coarse | coarse sand | flat-bottom batch drip |
| Medium | sand | cone pour-over, batch drip |
| Medium-fine | table salt | pour-over cone, AeroPress |
| Fine | caster sugar | espresso, moka pot at the finer end |
| Very fine | powder | Turkish coffee |
Ratio in grams per litre
Ratio states the dry coffee mass in relation to the water volume. The SCA target is 55 g of coffee per litre of water, with a permitted range of plus or minus 10 percent. A higher coffee share gives the water more coffee material relative to its volume. A lower share gives the finished drink less dissolved coffee material relative to the water. This is a strength adjustment, not automatically an extraction adjustment.
A scale helps keep both parts of the relationship stable. Weigh the coffee and the water using the same units, then keep the grind and method unchanged while judging the result. The ratio card provides the reference window without requiring every table value to be memorised. If a cup tastes sharp or harsh, changing ratio first can hide a grind or flow problem rather than solve it.
| Brew strength (TDS) | 1.15-1.35 percent, that is 11.5-13.5 g of dissolved solids per litre |
|---|---|
| Extraction yield | 18-22 percent of the dry coffee mass dissolved into the cup |
| Brew ratio | 55 g of coffee per litre of water, plus or minus 10 percent |
| Brew water temperature | 91-96 C, that is 195-205 F, measured in the brewer |
| Brew water | clean, odour free, no chlorine or chloramines |
Extraction yield and strength are different things
Strength describes how much dissolved coffee is present in the brewed drink, expressed as total dissolved solids. The SCA target window is 1.15-1.35 percent, or 11.5-13.5 g of dissolved solids per litre. Extraction yield describes the share of the dry coffee mass that entered the cup, with a target of 18-22 percent. One measure concerns concentration in the drink; the other concerns how much was removed from the grounds.
A drink can taste weak because the ratio uses too much water, even when the grounds were extracted within the target window. It can also taste strong while extraction is uneven. Grind distribution, water movement, and method affect extraction, while the coffee-to-water relationship strongly affects strength. Treat the two measures as separate clues. Adjust concentration with ratio and extraction behaviour with grind, flow, or method.
Fixing a sour cup
Sourness can point to insufficient or uneven extraction, particularly when the cup seems thin and sharply acidic. Begin with the method's listed grind reference and move a little finer if the bed appears to release too little material. Keep the ratio fixed during that test. A narrower burr-grinder distribution can also make the adjustment easier to interpret because fewer large particles remain under-extracted beside fine particles.
Water quality and temperature are part of the same diagnosis. Brewing water should be clean, odour free, and without chlorine or chloramines. The SCA temperature window is 91-96 C, or 195-205 F, measured in the brewer. If those conditions are already in place, change only grind or flow behaviour. A sour cup does not automatically call for more coffee, because more coffee changes strength rather than directly correcting extraction.
- Check the coffee-to-water ratio before changing the grind.
- Move slightly finer while keeping the method and ratio steady.
- Confirm that brewing water is clean and odour free.
- Keep water within 91-96 C in the brewer.
- Use a burr grinder when particle consistency is the main uncertainty.
Fixing a bitter cup
Bitterness can point to excessive or uneven extraction, especially when the cup feels harsh rather than simply concentrated. Move toward a coarser setting while holding the ratio steady, then compare the result. Very fine particles can slow water movement and remain in contact longer than intended. A blade grinder may add dust that complicates the result, so the apparent setting may not describe the whole coffee bed.
Ratio still matters, but it answers a different question. If the cup is bitter and also too strong, reducing the coffee share can lower concentration without changing the extraction pattern. If the cup is bitter at a suitable strength, begin with grind or flow instead. Keep the water within the SCA range of 91-96 C, measured in the brewer, and avoid changing temperature and grind together.
- Move slightly coarser while keeping the ratio unchanged.
- Check whether very fine particles are slowing the coffee bed.
- Separate a strength problem from an extraction problem.
- Use the table's method reference as the next setting.
- Change one brewing variable at a time.
Frequently asked questions
How much coffee per cup?
Use the ratio reference rather than an undefined cup measure. The SCA brewed-coffee target is 55 g of coffee per litre of water, plus or minus 10 percent. Weighing both ingredients keeps the relationship repeatable. The amount in a single serving depends on the water volume used for that serving.
Do I need a scale?
A scale is not required to operate a brewer, but it makes the ratio measurable. Weighing coffee and water lets you hold the coffee-to-water relationship steady while changing grind size. That separates a strength adjustment from an extraction adjustment and makes the table's grind references more useful.
Why is my coffee weak?
Weak coffee may contain too much water relative to the dry coffee, placing the ratio outside the intended range. It may also reflect low dissolved solids from uneven contact or a coarse grind. Check the ratio first, then inspect grind consistency and water movement without changing several variables at once.
Can I reuse grounds?
Reusing grounds does not provide the same starting material as fresh dry coffee. The first brew has already removed part of the soluble coffee from the bed, so a later pass changes the extraction conditions. The result is difficult to compare with a measured brew made from unused grounds.
How fine is too fine?
Very fine resembles powder in the grind reference and is associated with Turkish coffee. It is too fine for a method when it restricts water movement or creates an uneven, harsh result. Choose the table's method range first. For espresso, fine is the reference, while moka pot sits at the finer end.
The Home Coffee Bench keeps grind, ratio, water, and method in view as separate but connected controls. jdrcr.com is an independent, non-commercial informational reference, and this version was reviewed on September 6, 2026. Use the measured targets as a clear starting point, then adjust one variable at a time.
How this guide is built
Every figure on this site is checked against a named public reference before publication. Brewing strength, extraction yield, ratio, water temperature and water chemistry follow the Specialty Coffee Association standards. Espresso parameters follow published dose, yield, temperature, pressure and time references. Caffeine amounts and decaffeination routes follow food-science and published reference material. Storage and degassing windows follow roaster guidance. The reference families are listed on the about page. Last reviewed: September 6, 2026.