How do I measure coffee strength?

In the specialty coffee industry, 'strength' and 'extraction' are two distinct concepts that are often confused. Strength refers to the concentration of the coffee—how much coffee material is dissolved in the water. Extraction refers to how much of the available flavor compounds you have pulled out of the grounds. You can have a strong, under-extracted cup, or a weak, over-extracted cup. Measuring these accurately is the hallmark of a professional.

The industry standard for measuring strength is TDS, or Total Dissolved Solids. This is measured using a digital refractometer, which uses light to determine the percentage of dissolved coffee solids in the liquid. Most filter coffee falls into a TDS range of 1.2% to 1.5%. This means that 98.5% to 98.8% of your cup is water, and the remaining small percentage is the coffee flavor. It is a surprisingly small amount of material that creates such a complex flavor profile.

For the home brewer, you don't necessarily need a refractometer to manage strength. You can control it by adjusting your brewing ratio. A common starting point is 60 grams of coffee per liter of water (a 1:16.6 ratio). If you find your coffee is too weak, you can increase the amount of coffee (e.g., 1:15 ratio) or grind finer to increase extraction. If it is too strong, you can decrease the coffee (e.g., 1:18 ratio) or grind coarser.

In practice, measuring strength is about consistency. By using a scale to weigh both your coffee and your water, you remove the guesswork from your brewing. This allows you to replicate your favorite cup every single morning. Once you have a consistent ratio, you can then start experimenting with grind size and water temperature to fine-tune the extraction. Understanding these numbers doesn't make coffee less of an art; it simply gives you the tools to ensure that your art is repeatable and delicious.