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Coffee strength is the concentration of dissolved coffee in the cup, while extraction yield is the share of the dry grounds that actually made it into the drink. Those two numbers matter because a brew can taste thin, heavy, sharp, or dull for different reasons, and the right correction depends on whether the problem is concentration, extraction, or both. This calculator turns a weighed dose, a final beverage mass, and a refractometer reading into a brew result you can compare against a chosen target zone.
That is useful when a recipe looks close on paper but the cup still feels off. A 20 g filter brew that lands at 320 g in the cup and reads 1.35% TDS is a very different situation from an espresso that lands at 36 g and reads 9.5% TDS, even if both were brewed with care. The page makes those situations legible by showing strength, extraction, ratios, dissolved solids, and a status summary together.
It also handles the messy parts that often get skipped in casual brew math. If your refractometer reports Brix instead of percent total dissolved solids, the reading can be converted with an adjustable factor. If part of the final cup came from bypass water, or if you want to override inferred brew water with a measured value, the advanced inputs let you do that without rebuilding the whole calculation.
The practical payoff is faster dial-in work. The tool can place the current brew against an SCA-style filter box, a fuller-bodied filter range, an immersion range, or an espresso range, then suggest whether the next move should mainly change concentration, extraction intensity, or a process assumption such as retained water. That is enough to make one measured adjustment instead of changing several variables at once.
The result is still only as trustworthy as the numbers behind it. The page does not measure grind size, water chemistry, roast development, or sample handling, and it cannot tell you whether a cup will taste sweet, bitter, or sour. It works best as a brew-analysis aid for weighed recipes and plausible refractometer readings, not as a substitute for tasting or for a controlled lab protocol.
Start with the preset closest to the brew you actually made. The filter, espresso, and immersion presets load realistic starting values for dose, beverage mass, reading range, and retained-water assumptions, which makes the first pass much faster than starting from a blank custom recipe.
% TDS when your meter reports coffee strength directly. Switch to Brix (°Bx) only when that is the scale your instrument provides, then verify the conversion factor before you trust the number.Bypass water instead of pretending the whole cup came straight from the bed. That keeps dilution from looking like a different extraction result.Status, Strength delta vs target center, and Extraction delta vs target center together. The badge is convenient, but the paired deltas tell you whether the next move should change water and dose or grind and contact time.The most common misread is to treat a strong cup as automatically well extracted. Concentration and extraction are related, but they are not interchangeable. A cup can be concentrated because beverage yield is low, yet still fall short on extraction if the bed did not give up enough dissolved solids. The reverse can happen with a more dilute beverage that still extracted heavily.
Before you act on the dial-in suggestions, verify the Refractometer input row and the Total brew water note. If the scale, correction factor, or water assumption is wrong, the recommendations will be numerically tidy and practically wrong.
The page follows the brew-analysis idea behind the brewing control chart: strength comes from how much dissolved coffee is present in the finished beverage, and extraction yield comes from how much of the dry dose those dissolved solids represent. Those two coordinates let one brew point be compared against a target rectangle instead of judged only by ratio or by memory.
In this implementation, the refractometer reading is the starting point. A direct % TDS reading is used as entered. A Brix (°Bx) reading is first multiplied by the user-selected Brix → TDS factor, then adjusted by the optional Reading correction. That corrected strength percentage is converted into dissolved solids in grams by multiplying it by the final beverage mass.
Water accounting is handled separately from concentration. The calculator estimates retained water as Absorption ratio × coffee dose, then uses beverage mass, optional bypass water, and optional measured brew water to report both Water to coffee ratio and Beverage ratio (in-cup). That distinction matters because the same 20 g dose can read roughly 18:1 at the brewer and 16:1 in the cup once retained water is considered.
| Symbol | Meaning | Package field or result |
|---|---|---|
R |
Entered refractometer reading | Refractometer reading |
F |
Brix-to-TDS multiplier or 1 for direct TDS | Brix → TDS factor |
c |
Reading correction percentage | Reading correction |
B |
Final beverage mass | Beverage mass |
D |
Dry coffee dose | Coffee dose |
T |
Corrected strength percentage | Strength (TDS) |
S |
Dissolved solids in the beverage | Dissolved solids extracted |
E |
Extraction yield | Extraction yield |
a |
Retained water per gram of coffee | Absorption ratio |
Wtotal |
Manual or inferred total brew water | Total brew water |
When Measured brew water is greater than zero, Total brew water uses that manual value. Otherwise the page infers total water from beverage mass and retained water, while Bypass water prevents post-brew dilution from being mistaken for a different extraction process.
| Target profile | Strength range | Extraction range | Package note |
|---|---|---|---|
| SCA filter target | 1.15% to 1.45% TDS | 18% to 22% | Default auto target for the filter preset. |
| Filter full-body target | 1.30% to 1.60% TDS | 18.5% to 22.5% | Shifts strength upward for a heavier cup. |
| Immersion balanced target | 1.25% to 1.55% TDS | 18% to 22% | Default auto target for the immersion preset. |
| Modern espresso target | 8% to 12% TDS | 19% to 23% | Default auto target for the espresso preset. |
Status compresses the brew point into Inside ideal box, Under target, or Over extracted, while the chart keeps the full two-axis picture. Dial-In Moves then translates the deltas into practical next steps: concentration changes point toward dose or water edits, extraction changes point toward grind or contact time, and unusually high retained-water loss adds a process check.
Use the page in this order so the result reflects the brew you actually made rather than a tidy but mismatched model.
Brew preset first. Start with filter, espresso, or immersion when one of those matches the brew style, and switch to Custom only after you have a useful baseline.Coffee dose, Beverage mass, and Refractometer reading. Select % TDS or Brix (°Bx) so the calculator reads the measurement on the correct scale.Advanced only for things that materially change the math, such as Bypass water, Measured brew water, Brix → TDS factor, or Reading correction.Strength Metrics tab next. Confirm Strength (TDS), Extraction yield, the two delta rows, and the Refractometer input row all describe the same brew story.Coffee Strength Map and Dial-In Moves for the next recipe change. If the point sits outside the target boundary, change one major variable, brew again, and compare the new point against the old one.The most reliable workflow is one controlled adjustment at a time, because the page is best at showing which change moved the brew point and which change only added noise.
Start with the pair Strength (TDS) and Extraction yield, not with either number in isolation. If both sit inside the chosen target profile, the brew is in a conventional starting zone for that style. If one or both sit outside the box, the delta rows tell you whether the next correction is mainly about concentration, extraction intensity, or both.
Strength delta vs target center tells you how far the cup concentration sits from the middle of the chosen band.Extraction delta vs target center tells you whether the brew pulled less or more soluble material than the target center.Water retained/lost is a trust check. A high value can mean your absorption or bypass assumptions deserve another look before you change the grinder.What the result does not mean is "flavor solved." A point inside the box can still taste unpleasant, and a point outside the box can still taste good for a specific bean or brew style. When the numbers look surprising, verify the scale selection, correction, and beverage mass before making a dial-in decision.
A 20 g dose, a 320 g beverage, and a 1.35% TDS reading produce 4.32 g of dissolved solids and a 21.60% extraction yield in this package. With the default 2.0 g/g absorption assumption, the page reports an 18.00:1 water ratio, a 16.00:1 in-cup beverage ratio, and Inside ideal box against the SCA-style filter target. That is a good example of a brew that is both conventionally strong enough and conventionally well extracted.
A 20 g dose, a 360 g final beverage, a 1.10% TDS reading, and 40 g of bypass water produce a 19.80% extraction yield and a 20.00:1 total water ratio here. Without the bypass entry, the same final cup would look like a different brew process. Entering bypass keeps dilution from masquerading as lower extraction.
An 18 g dose, a 36 g beverage, and a 9.50% TDS reading on the espresso preset produce 3.42 g dissolved solids and exactly 19.00% extraction. The brew lands on the low edge of the package's modern espresso range, while Water retained/lost rises above 35%, which is why the process check can matter more here than the headline strength number.
Water to coffee ratio and Beverage ratio (in-cup) differ?Because the calculator tracks retained water separately. Water to coffee ratio uses total brew water, while Beverage ratio (in-cup) uses only what made it into the finished drink. The gap between them grows when absorption is high.
Measured brew water override the inferred value?Use it when you truly know the total water added during brewing and want the ratio math to follow that measured amount. Leave it at 0 when you want the page to infer water from beverage mass, retained water, and bypass assumptions.
Switch the scale to Brix (°Bx) and confirm the Brix → TDS factor before you compare brews. The package uses your chosen multiplier, so the factor directly changes the reported TDS and extraction yield.
Because concentration alone does not guarantee adequate extraction. A beverage can be heavy because yield is low, yet still sit below the target extraction band. That is why the page shows strength and extraction separately instead of collapsing them into one score.
No server-side processing is present for this calculator. The calculations shown in the summary, table, chart, and JSON payload are generated in the browser from the values you enter.