Coffee Strength Calculator

Brew preset:

Pick filter, espresso, or immersion; choose Custom after entering your own measurements.

Target profile:

Choose the brew-control box used for diagnosis and the next-brew target.

Aim point:

Lower, center, or upper target changes the delta and recipe plan.

Coffee dose:

Weigh the coffee before brewing, e.g. 20.0 g filter or 18.0 g espresso.

Beverage mass:

Weigh the liquid in the cup after brewing, including any post-brew bypass already mixed in.

Refractometer reading:

Enter % TDS directly, or enter °Bx and select Brix so the conversion factor is applied.

Input notes

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Measured brew water:

Enter grams of water poured, or keep 0 to infer from beverage, retention, and bypass.

g (0 = auto)

Absorption ratio:

Set retained water per gram of coffee, such as 2.0 g/g filter or 1.1 g/g espresso.

{{ formatNumber(absorption_ratio, 2) }} g/g

Bypass water:

Enter grams of water added after extraction; use 0 when the cup was not diluted.

Brix to TDS factor:

Most coffee Brix workflows use about 0.85-0.86; keep your lab's documented factor.

Reading correction:

Use 0% for a trusted meter; apply small positive or negative offsets only when documented.

{{ formatNumber(reading_correction_percent, 1) }}%

Beverage density:

Keep 1.000 g/mL unless you have a measured espresso or concentrated brew density.

g/mL

Metric	Value	Copy
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Focus	Adjustment	Target	Why	Copy
{{ row.focus }}	{{ row.adjustment }}	{{ row.target }}	{{ row.reason }}
Provide valid inputs to generate a next-brew plan.

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A cup can taste weak, heavy, sour, or bitter for reasons that look similar at the tasting table but separate cleanly on a brew-control chart. Strength describes how concentrated the finished drink is. Extraction yield estimates how much of the dry coffee dose moved into that drink. The first number says how dense the cup is; the second says how much soluble material was pulled from the grounds.

In coffee measurement, strength usually means total dissolved solids, or TDS. A 1.30% filter coffee contains about 1.30 g of dissolved coffee solids in every 100 g of beverage. Espresso often sits much higher because a similar dry dose is concentrated into a much smaller cup. Bypass water, beverage mass, and brew ratio can all change the concentration without proving that the coffee extracted evenly.

Brew control map with cup strength on the vertical axis and extraction yield on the horizontal axis. — Coffee strength and extraction yield describe different parts of the same brew.

Refractometers make the numbers practical, but the sample and brew record still matter. Dry coffee dose, finished beverage mass, dilution water, retained water in the grounds, and the meter scale all change the calculation. Filter coffee is often discussed around an SCA-style brew-control area, espresso uses much higher TDS because the beverage is small, and immersion methods can behave differently because all the water and grounds steep together before separation.

Common coffee strength terms and why they matter
Term	Plain meaning	Common mistake
Total dissolved solids	Concentration of dissolved coffee in the finished beverage.	Reading it as a flavor score instead of a concentration number.
Extraction yield	Dry coffee mass that ended up dissolved in the cup.	Ignoring uneven extraction, channeling, fines, or poor sampling.
Brew ratio	Relationship between coffee dose and water or beverage mass.	Mixing up poured water ratio with finished beverage ratio.
Bypass water	Water added after extraction to dilute the cup.	Treating dilution as if it extracted more coffee from the grounds.

Measurement works best as a repeatable brew note, not a final verdict. The numbers can reveal that a sour cup is concentrated but under-extracted, or that a thin cup has enough extraction but too much beverage mass. They cannot prove sweetness, clarity, balance, or even saturation on their own.

How to Use This Tool:

Start with a measured brew and change the advanced fields only when you have a reason to override the defaults.

Choose Brew preset first. Filter, espresso, and immersion presets set realistic starting dose, beverage, meter scale, and absorption values; Custom keeps your current numbers.
Set Target profile and Aim point. The target profile chooses the brew-control band, while the aim point selects the lower, center, or upper part of that band for the next-brew plan.
Enter Coffee dose, Beverage mass, and Refractometer reading. Use grams for dry dose and finished beverage mass, then select % TDS or Brix to match the meter display.
Open Advanced for measured brew water, absorption ratio, bypass water, Brix to TDS factor, reading correction, or beverage density. Leave measured brew water at 0 when you want the calculator to infer total water from beverage mass, retained water, and bypass.
Check Input notes before trusting the result. Fix impossible or unlikely entries such as zero strength, bypass water at or above beverage mass, measured brew water below beverage mass, or a Brix factor far outside common coffee use.
Read Brew Analysis for the metric table, Strength Map for the brew-control plot, Next Brew Plan for practical adjustments, and JSON when you need a structured record.
Repeat the brew with the same sample filtering, meter temperature routine, density assumption, and target profile when you want Strength delta vs aim or Extraction delta vs aim to reflect recipe changes rather than measurement drift.

Interpreting Results:

Use Strength (TDS) for concentration and Extraction yield for how much of the dry dose dissolved. The Diagnosis compares both values against the selected target band, while the two delta rows show how far the brew is from the chosen aim point.

Coffee strength map interpretation guide
Map position	Likely meaning	First thing to verify
Inside strength and extraction bands	The brew is close to the selected target profile.	Confirm the cup tastes balanced before locking the recipe.
Low strength, low extraction	The cup is probably thin and underdeveloped.	Check grind size, brew time, saturation, and beverage mass.
High strength, low extraction	The cup can taste dense but sharp, sour, or incomplete.	Raise extraction before adding dilution as the only fix.
Low strength, high extraction	The brew may be watery while still tasting bitter or drying.	Check whether the beverage mass or bypass water is too high.
High strength, high extraction	The cup can be heavy, bitter, or tiring to drink.	Back off extraction pressure before changing dose alone.

A good-looking coordinate is not proof of good coffee. A refractometer averages the sample, so it cannot show channeling, uneven saturation, sediment, roast defects, water chemistry problems, or whether the cup tastes pleasant.

Treat Next-brew target beverage, Next-brew total water, and the plan rows as controlled starting points. Make one recipe change at a time, then compare the next brew against the same profile and aim point.

Technical Details:

Brew strength is mass concentration. The calculation turns the meter reading into effective TDS, turns TDS and beverage mass into dissolved-solids mass, then divides those solids by the dry coffee dose to estimate extraction yield. Recipe water is accounted for separately because water can remain in the grounds or be added after brewing without dissolving more coffee.

The selected target profile supplies a rectangle on a brew-control map: extraction yield on the horizontal axis and strength on the vertical axis. Values on the lower or upper edge count as inside the target band; only values below the lower edge or above the upper edge are classified as low or high.

Formula Core:

The primary equation estimates effective TDS, dissolved solids, extraction yield, retained water, and water ratios from the entered brew record.

\begin{array}{lcl} T & = & R \times F \times (1 + \frac{c}{100}) \\ S & = & B \times \frac{T}{100} \\ E & = & \frac{S \times 100}{D} \\ W_{retained} & = & a \times D \\ Q_{beverage} & = & \frac{B}{D} \\ Q_{water} & = & \frac{W_{total}}{D} \end{array}

Coffee strength formula symbol map
Symbol	Meaning	Unit or source
`R`	Refractometer reading	% TDS or °Bx, depending on the selected scale
`F`	Scale factor	1 for % TDS, or the Brix to TDS factor for Brix readings
`c`	Reading correction	Percent offset applied before result diagnosis
`B`	Beverage mass	Finished drink in grams
`D`	Coffee dose	Dry coffee in grams
`a`	Absorption ratio	Retained water in grams per gram of dry coffee

With a 20.0 g filter dose, 320.0 g beverage mass, and 1.35% TDS reading, dissolved solids are 320.0 × 0.0135 = 4.32 g. Extraction yield is 4.32 × 100 / 20.0 = 21.60%. With the default 2.0 g/g absorption setting and no bypass water, retained water is 40.0 g and total brew water is inferred as 360.0 g, or an 18.00 : 1 water-to-coffee ratio.

Target and Rule Core:

Coffee strength target profiles used by the calculator
Target profile	Strength lower	Strength upper	Extraction lower	Extraction upper
SCA filter target	1.15% TDS	1.45% TDS	18.0%	22.0%
Filter full-body target	1.30% TDS	1.60% TDS	18.5%	22.5%
Immersion balanced target	1.25% TDS	1.55% TDS	18.0%	22.0%
Modern espresso target	8.00% TDS	12.00% TDS	19.0%	23.0%

The aim point is set at 25%, 50%, or 75% of the selected strength and extraction ranges. For example, the center of the SCA filter target is 1.30% TDS and 20.0% extraction. Strength-only planning keeps current dissolved solids fixed and solves for target beverage mass. Extraction-only planning solves for target dissolved solids from dose and aim-point extraction. The full target recipe solves for both target dissolved solids and target TDS, then estimates the beverage and total water needed with the current retention and bypass settings.

Coffee strength validation and warning rules
Condition	Why it matters
Dose, beverage mass, or effective TDS is zero	The main calculation cannot produce a useful brew analysis.
Effective TDS is above 15%	The reading is unusual enough that the scale or sample should be checked.
Bypass water is greater than or equal to beverage mass	Dilution water cannot reasonably equal or exceed the final drink mass.
Measured brew water is below final beverage mass	Poured water should not be less than the beverage captured in the cup.
Brix factor is below 0.75 or above 0.95	Common coffee Brix conversion factors are around 0.85-0.86.
Non-espresso TDS is above 3%, or espresso TDS is below 4%	The preset, reading scale, or sampling method may not match the brew style.

Beverage density affects only the displayed beverage volume estimate. It does not change Strength (TDS), dissolved solids, extraction yield, or either ratio because those calculations are mass based.

Accuracy Notes:

Refractometer results depend on a clean prism, a well-mixed sample, suitable filtration for espresso or sediment-heavy brews, and a sample temperature routine that matches the meter. A hot, gritty, or unrepresentative sample can move TDS enough to change the extraction yield and map diagnosis.

Use target bands as brew-control guides, not sensory guarantees.
Record whether total brew water was measured or inferred before comparing sessions.
Keep Brix conversion and correction offsets documented if your meter workflow requires them.
Check taste and repeatability before making large grinder, ratio, or bypass changes.

Worked Examples:

Filter brew near the target box

A 20.0 g filter dose, 320.0 g beverage mass, and 1.35% TDS reading gives Strength (TDS) of 1.35%, Dissolved solids extracted of 4.32 g, and Extraction yield of 21.60%. The default SCA filter target treats that as inside the target band, though the center aim still shows a positive extraction delta.

Espresso with enough strength but low-center extraction

An 18.0 g dose, 36.0 g beverage, and 9.50% TDS reading reports Extraction yield of 19.00%. That is inside the modern espresso target range, but the center aim row shows an Extraction delta vs aim of -2.00%, so the next adjustment should focus on extraction before judging the shot by strength alone.

Brix entry that changes the diagnosis

If a filter sample reads 1.60 °Bx but the scale is left on % TDS, the result becomes 1.60% TDS and 25.60% extraction for a 20.0 g dose and 320.0 g beverage. Switching Refractometer reading to Brix with a 0.85 factor changes Strength (TDS) to 1.36% and Extraction yield to 21.76%, which is a very different brew-control reading.

Dilution entry that should be fixed first

A 300.0 g beverage with 300.0 g of bypass water triggers the input note about bypass water being greater than or equal to final beverage mass. Correct that field before using Next-brew target beverage or Next-brew total water, because the water accounting is no longer credible.

FAQ:

Can strength alone tell me whether the coffee is good?

No. Strength (TDS) tells you concentration, while Extraction yield estimates how much of the dry dose dissolved. Use the Diagnosis and the Strength Map together, then taste the cup for balance and evenness.

Should I enter beverage mass or brew water?

Enter Beverage mass for the finished drink in the cup. Measured brew water is an Advanced field for the water poured into the brew; when it stays at 0, total water is inferred from beverage mass, retention, and bypass water.

Why does a Brix factor warning appear?

The warning appears when the Brix to TDS factor is below 0.75 or above 0.95. Coffee workflows commonly use about 0.85-0.86, so a wider value should be checked against your meter or lab notes.

Why does the espresso preset use much higher TDS?

Espresso has a small beverage mass relative to the dose, so the same dissolved-solids math produces a much higher Strength (TDS) range. The modern espresso target in this calculator uses 8% to 12% TDS and 19% to 23% extraction.

Does bypass water change extraction yield?

Bypass water is included in beverage mass after dilution, but it does not extract more solids from the coffee bed. It mainly lowers concentration and changes the inferred water accounting, so enter it only when water was added after extraction.

Glossary:

Total dissolved solids: The concentration of dissolved coffee solids in the beverage, shown as Strength (TDS).
Extraction yield: The percent of dry coffee dose that dissolved into the finished drink.
Beverage ratio: Finished beverage mass divided by dry coffee dose.
Total brew-water ratio: Measured or inferred total brew water divided by dry coffee dose.
Bypass water: Water added after extraction to dilute the beverage.
Brix: A refractometer scale that can be converted to coffee TDS with a documented factor.

References:

SCA Coffee Standards, Specialty Coffee Association.
SCA's Minimum Certification Requirements for Coffee Brewers, Specialty Coffee Association, 2017.
Brew temperature, at fixed brew strength and extraction, has little impact on the sensory profile of drip brew coffee, Scientific Reports, 2020.
An equilibrium desorption model for the strength and extraction yield of full immersion brewed coffee, Scientific Reports, 2021.
VST Coffee Refractometer Specs, VST.
PAL-COFFEE(BX/TDS) instruction manual, ATAGO.

Coffee Strength Calculator

Dial-In Snapshot

Current result

How to Use This Tool:

Interpreting Results:

Technical Details:

Formula Core:

Target and Rule Core:

Accuracy Notes:

Worked Examples:

Filter brew near the target box

Espresso with enough strength but low-center extraction

Brix entry that changes the diagnosis

Dilution entry that should be fixed first

FAQ:

Glossary:

References:

Coffee Strength Calculator

Dial-In Snapshot

Current result

Coffee strength primer

How to Use This Tool:

Interpreting Results:

Technical Details:

Formula Core:

Target and Rule Core:

Accuracy Notes:

Worked Examples:

Filter brew near the target box

Espresso with enough strength but low-center extraction

Brix entry that changes the diagnosis

Dilution entry that should be fixed first

FAQ:

Glossary:

References: