Coffee Strength & Extraction Calculator

Have a refractometer reading? Turn dose, beverage weight and TDS into extraction yield — and see exactly where your brew sits on the Golden Cup chart.

extraction analysis
Dose — dry coffeeg
Beverage weight — liquid outg
TDS — refractometer reading9.0 %
Extraction yield
18.0 %
Extraction yield = TDS × beverage weight ÷ dose
Strength (TDS)9.0 %
Extraction18.0 %
Ratio1 : 2.0
ZoneBalanced
This shot sits in the ideal window: high strength, moderate extraction. If it tastes flat rather than rich, grind a little finer.
GOLDEN CUP 1.00 1.15 1.30 1.45 1.60 1.75 14 18 22 26 STRENGTH · TDS % EXTRACTION YIELD %

Reference lines: the Golden Cup band is 1.15–1.45% TDS at 18–22% extraction. Filter coffee normally lands 1.25–1.45%, espresso 8–12%.

The formula

extraction yield % = (TDS % × beverage weight) ÷ dose weight

Everything is in grams. A 18 g dose yielding 36 g of espresso at 9% TDS gives:

0.09 × 36 ÷ 18 = 0.18 → 18% extraction

Strength and extraction are different things. Strength is how concentrated the liquid is — the TDS reading. Extraction is how much of the dry coffee actually dissolved into the cup. You can have a weak cup that is over-extracted, or a strong cup that is under-extracted, and the chart separates those two failures.

Reading the chart

  • Bottom-left — weak and under-extracted. Classic under-dose or too-coarse grind. Grind finer, add coffee.
  • Top-left — strong but under-extracted. Sour, salty, hollow. Grind finer or extend contact time.
  • Bottom-right — weak and over-extracted. Bitter but thin. Often too much water; shorten the ratio.
  • Top-right — strong and over-extracted. Harsh, drying. Grind coarser or drop temperature.

A note on refractometers

Optical refractometers read filtered coffee reasonably well, but espresso needs a correction: the standard VST model applies roughly a 0.5–1.0 percentage point coefficient, and unfiltered turbidity throws readings high. Treat a single reading as a hint, not a verdict — two readings on the same sample should agree within 0.1% before you trust either.

If the number disagrees with your palate, believe the palate. Refractometers measure dissolved solids; they cannot measure whether a coffee is pleasant.

Frequently asked

What is a good extraction yield for espresso?
18–22% is the traditional target, but modern light-roast espresso often runs 20–24% with longer ratios and higher temperatures. Anything under 17% usually tastes sour and hollow; over 24% starts to taste dry and papery.
Do I need a refractometer?
No. A scale and your tongue get you 90% of the way. A refractometer is useful when you want to hold strength constant while testing grind changes, or when you are training staff and need an objective number.
Why is my TDS reading different every time?
Usually sample temperature — refractometers are calibrated around 20 °C, and a hot sample reads several tenths high. Let the coffee cool, stir, filter if needed, and take two or three readings.

Grind size chart

Which grind for which brewer, from Turkish to cold brew.

Coffee ratio chart

Nine brew methods, dose and water in grams. Printable.

Basket size chart

Correct dose for every espresso basket size.

Not sure what ratio to pull?

The espresso ratio calculator gives you the dose and yield in grams before you ever touch the scale.

Open espresso calculator