Extraction Yield and TDS Explained: Describing Coffee with Numbers
We describe coffee as strong, weak, sour or bitter. TDS and extraction yield are the numbers behind those impressions. They look similar but measure different things, and knowing the difference helps you decide which way to change a recipe.
1. How the two numbers differ
- TDS (Total Dissolved Solids): the concentration (%) of dissolved coffee in the finished cup — how strong it is.
- Extraction yield: the share (%) of the coffee's mass that dissolved into the water — how much you pulled out of the beans.
With the same beans, adding more water lowers TDS (weaker) but can raise yield. Strength and extraction have to be looked at separately.
2. The extraction yield formula
Extraction yield (%) = TDS (%) × brewed coffee weight (g) ÷ dose (g)
Example: 20 g of coffee yielding 300 g of brew at 1.35% TDS gives 1.35 × 300 ÷ 20 = 20.25%.
The ratio calculator on this site gives, for a 20 g dose at 1:16, 320 ml of water and an estimated yield of about 280 ml (assuming the grounds hold about twice their weight in water). If you measured 1.40% TDS, the yield would be estimated at 1.40 × 280 ÷ 20 = 19.6%. The estimated volume is an assumption — weigh the finished coffee for accuracy.
3. Widely cited targets
The SCA (Specialty Coffee Association) Golden Cup standard is widely cited as targeting TDS of 1.15–1.35% and an extraction yield of 18–22%. This range marks where many people find coffee balanced; coffee outside it is not necessarily bad, and you may prefer different values depending on the beans and your taste.
4. General tendencies when the cup tastes off
- Sour, thin, salty, lacking sweetness: common when under-extracted (low yield).
- Bitter and dry: common when over-extracted (high yield).
- Overall watery: low strength — use less water or more coffee to change the ratio.
These are tendencies, not diagnoses; freshness, water and equipment can cause the same symptoms.
5. Variables that move yield
- Grind size: finer generally raises yield.
- Water temperature: hotter generally raises yield.
- Brew time: longer generally raises yield.
- Ratio: more water per gram of coffee lowers strength (TDS).
Changing several at once hides what worked, so change one at a time and keep notes.
6. How is TDS measured?
TDS is measured with a refractometer. At home, most people adjust by taste without any device, and you can improve a recipe a lot without measuring. Treat the numbers as a tool for describing taste.