Coffee Ratio Calculator
Calculates coffee and water by weight for any brew ratio, corrects for the water your grounds keep, and tests the result against the SCA Golden Cup standard.
Coffee Ratio Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Retention is a single figure applied uniformly. Real retention varies with brewer geometry, filter type, grind size and how completely the bed drains, so treat the cup yield as approximate to within a few percent.
- Extraction yield from a refractometer assumes the reading is taken on a properly mixed, cooled sample. Readings on hot or unstirred coffee are unreliable.
- The calculator does not model grind size, water chemistry or agitation, all of which move extraction substantially at a fixed ratio.
- Method defaults are conventions, not standards. Regional and individual preference varies widely and legitimately.
In short: Weigh both. The specialty default is 1:16 to 1:17 by weight — about 60 g of coffee per litre — while the SCA Golden Cup standard specifies 55 g/L, or 1:18.2. Note that the grounds keep roughly twice their own weight in water, so a 15 g dose brewed with 250 g of water yields only about 220 g in the cup.
Formula
[('ratio', 'Parts of water to one part of coffee, by weight. 1:16 to 1:17 is the specialty norm; the SCA figure of 55 g/L is 1:18.2.'), ('retention', 'Water absorbed by the spent grounds and never poured, typically twice the dry coffee weight.'), ('TDS', 'Total dissolved solids, the strength of the liquid, measured with a refractometer. The Golden Cup band is 1.15 to 1.35%.'), ('extraction yield', 'The percentage of the dry coffee that dissolved. Conventionally 18 to 22%. It is a different axis from strength.')]
Worked Example
- Weigh the coffee. In grams, after grinding if you like, though grinding loses very little. A volume scoop is not a substitute: bean density varies with roast level and origin.
- Multiply by the ratio. 1:16 means 16 g of water for every gram of coffee. 30 g of coffee takes 480 g of water. Water can be poured straight onto the scale at 1 g per millilitre.
- Account for what the grounds keep. Subtract about twice the coffee weight from the water to get what actually reaches the cup. This is the step that explains why your brew always seems to come up short.
- Adjust one variable at a time. Dose changes strength. Grind changes extraction. Changing both at once tells you nothing about either.
Two 240 ml cups of drip coffee means 480 g of finished beverage. At the 1:16.7 drip default, and allowing for grounds retaining twice their weight, the dose works out at 33 g with 545 g of water — not the 480 g of water a naive calculation would give. The 65 g difference is the water the spent grounds keep, and it is why brewing “two cups” so often produces noticeably less than two cups.
Strengths & Limits Of This Model
Where this engine is strong
- Solves in three directions, including backwards from the finished volume, which is the direction that needs retention.
- Makes the strength-versus-extraction distinction explicit rather than collapsing both into one “strength” slider.
- Tests the result against the published standard and explains where that standard is internally inconsistent.
Where it stops
- Extraction yield needs a refractometer, which most home brewers do not own.
- Cannot account for grind size, the single largest uncontrolled variable in the brew.
Practical Use Cases
Getting a repeatable cup
Fixing the ratio by weight removes the largest source of day-to-day variation, which is scoop-to-scoop inconsistency in the dose.
Brewing for a specific number of people
Working backwards from the finished volume, with retention included, is the only way to hit a target quantity of coffee.
Dialling in a new bag
Hold the ratio constant and move only the grind until the sourness or bitterness resolves, then adjust the ratio for strength.
Interpreting a refractometer
The extraction yield calculation turns a TDS reading into the number that actually describes what happened in the brewer.
Scaling a recipe to a larger brewer
Ratios hold across batch sizes, though contact time and grind usually need small adjustments as the bed depth changes.
Methodology & Editorial Standards
Brew ratios are expressed as parts of water to one part of dry coffee by weight, converted to grams per litre as 1000 divided by the ratio. Method defaults follow common specialty practice: drip and Chemex at 1:16.7, pour over and siphon at 1:16, French press at 1:15, AeroPress at 1:14 and moka pot at 1:8. The SCA Golden Cup figures are taken from the SCAA standard as revised 23 December 2015 — 55 g/L plus or minus 10%, TDS 1.15 to 1.35%, extraction yield 18 to 22%, water at 200°F plus or minus 5. Retention defaults to twice the dry coffee weight, within the commonly cited 1.8 to 2.2 range. Extraction yield uses the standard identity: TDS percentage multiplied by beverage mass, divided by dry dose. Water is treated as 1 g per millilitre.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Coffee Ratio Calculator — 11 Expert FAQs
11 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What is the best coffee to water ratio
For filter and immersion brewing, 1:16 to 1:17 by weight is the specialty default — about 60 grams of coffee per litre of water. The SCA Golden Cup standard is slightly weaker at 55 g/L, or 1:18.2. French press is usually brewed stronger at 1:13 to 1:16 because the metal filter lets more solids through, and a moka pot is stronger again at around 1:8. Start at 1:16, then adjust the ratio for strength and the grind for extraction.
How many grams of coffee per cup
For a 240 ml cup at 1:16, about 15 g of coffee and 240 g of water — but that yields only around 210 g in the cup once the grounds have absorbed their share. To actually fill a 240 ml cup you need roughly 17 g of coffee and 275 g of water. This gap is the single most common reason a brew comes up short of the expected volume.
Do coffee grounds really absorb that much water
Yes. Spent grounds retain roughly twice their own dry weight in water, with a realistic range of 1.8 to 2.2 times depending on the brewer and how thoroughly it drains. On a 30 g dose that is about 60 g of water that never leaves the filter — typically 11 to 12% of everything you poured. Immersion methods that you press or squeeze recover a little more; percolation methods generally retain the full amount.
What is the SCA Golden Cup standard
It specifies a brewing strength of 1.15 to 1.35% total dissolved solids, an extraction yield of 18 to 22%, a brewing ratio of 55 grams per litre plus or minus 10%, and water at 200°F plus or minus 5. Contact time is capped at roughly 8 minutes. It derives from research by Lockhart at the Midwest Research Institute in 1957 and remains the basis of most brewer certification programmes.
Is the Golden Cup standard still valid
It is a useful starting region but it should not be treated as a definition of good coffee, and it contains a genuine internal tension. Because strength, extraction and ratio are mathematically linked, a 1:15 brew produces a TDS above the specified band even at a perfect 20% extraction — yet 1:15 to 1:17 is where much of the specialty industry now brews. The pre-1957 figure was 17.5 to 21.2% and no methodology for the revision was ever published. A 2020 UC Davis study found consumer preference spread far more widely than the standard allows.
What is the difference between strength and extraction
Strength is how much dissolved coffee is in the liquid, measured as TDS. Extraction is what fraction of the dry coffee dissolved, measured as extraction yield. They are independent axes. A very concentrated brew can be badly under-extracted, and a weak brew can be over-extracted. Dose and ratio control strength; grind size, temperature and time control extraction. Confusing the two is why adjustments so often fail to improve anything.
Should I weigh coffee before or after grinding
Either, and it makes almost no practical difference — grinding loses well under a percent to retention in the burrs and static. Weighing beans before grinding is more convenient and avoids the mess. What matters is that you weigh at all: a level scoop of a light roast and a level scoop of a dark roast differ meaningfully in mass because roasting drives off water and expands the bean.
How much coffee for a full 1 litre French press
At the French press default of 1:15, about 67 g of coffee to 1,000 g of water. Note the press will not give you a litre of drink: the grounds retain around 134 g, so expect roughly 866 g in the cups. If you want a full litre of finished coffee, scale up to about 77 g of coffee and 1,155 g of water.
Does water temperature change the ratio
No, but it changes the extraction you get from that ratio. Cooler water extracts less, so a brew at 88°C will taste weaker and more sour than the same ratio at 95°C. The SCA specifies 93°C plus or minus 3. If you are consistently under-extracting, raising the temperature is a legitimate correction — but grind size is a stronger and more controllable lever.
Why does my coffee taste weak even at a strong ratio
Almost always under-extraction rather than insufficient coffee. If the cup is thin and also sour, sharp or empty-tasting, the water is not pulling enough out of the grounds — grind finer, use hotter water or extend the contact time. Adding more coffee at the same grind makes the cup more concentrated but no less sour, which is why the problem persists through repeated dose increases.
Can I measure coffee by tablespoons instead
You can, but it is imprecise. A level tablespoon of medium-ground coffee is roughly 5 to 7 g depending on roast, grind size and how it settles — a spread of 40% on the same nominal measure. The traditional “two tablespoons per 6 oz cup” works out somewhere between 1:13 and 1:18, which spans nearly the entire useful range. A scale that reads to 0.1 g costs very little and removes the problem entirely.