Berechne deine Wasserhärte aus Calcium und Magnesium oder rechne einen vorhandenen Härtewert um. Für Kaffee erhältst du zusätzlich eine Einschätzung passend zu deiner Zubereitungsart.
Wähle deine bevorzugte Methode
Kalzium & Magnesium bestimmen die GH
Bei Mineralwasser stehen Calcium, Magnesium und Hydrogencarbonat meist auf dem Etikett. Bei Leitungswasser findest du sie in der Trinkwasseranalyse deines örtlichen Wasserversorgers.
Hydrogencarbonat bestimmt die KH
Gib deine Wasserwerte ein und klicke auf „Wasser prüfen“.
Deine Analyse erscheint anschließend hier.Gib einen vorhandenen Härtewert ein und wähle die Einheit.
Gib deinen Härtewert ein, um ihn in die gängigen Einheiten umzurechnen.
Das Ergebnis erscheint anschließend hier.Gesamthärte (°dH) ≈ Calcium ÷ 7,14 + Magnesium ÷ 4,34
Beispiel: 40 mg/L Calcium + 10 mg/L Magnesium ergeben ca. 7,9 °dH Gesamthärte.
Karbonathärte (°dH) ≈ Hydrogencarbonat ÷ 21,8
With this water hardness calculator, you can calculate the general hardness (GH) and carbonate hardness (KH) of your water. Both values are crucial for the taste of your coffee.
General hardness influences extraction, while carbonate hardness regulates the acidity in the coffee. Water that is too hard often leads to a bitter taste and limescale deposits, while water that is too soft results in acidic and thin coffee.
Water makes up over 98% of your coffee – and yet it is often underestimated. While many people focus intensely on beans, roast profiles, or grinders, water quality frequently goes unnoticed. Yet, it is one of the decisive factors for flavor, extraction, and consistency.
The composition of the water influences how well flavor compounds are extracted from the coffee. If the water is not optimally adjusted, even a high-quality specialty coffee can taste flat, bitter, or unbalanced.
Two values are particularly relevant here: general hardness (GH) and carbonate hardness (KH). Both affect coffee in different ways – and should ideally be in the right ratio.
Total hardness describes the amount of dissolved minerals in water, particularly calcium (Ca²⁺) and magnesium (Mg²⁺). These minerals are essential for extracting flavors from ground coffee.
Magnesium is considered particularly "extraction-friendly" and brings out fruity and complex flavor notes. Calcium, on the other hand, contributes more to the body and structure of the coffee.
If the total hardness is too high, over-extraction can occur. The coffee then quickly tastes bitter, heavy, and lacks nuance. At the same time, the risk of limescale buildup in the machine increases. If, however, the total hardness is too low, the water lacks the ability to dissolve sufficient flavors – the coffee tastes thin, hollow, and under-extracted.
A balanced ratio ensures that the desired flavor compounds can develop optimally.
Carbonate hardness describes the proportion of hydrogen carbonate (HCO₃⁻) in water. It acts as a buffer and significantly influences how acidity is perceived in coffee.
A high KH value can lead to the neutralization of acids. As a result, the coffee loses its vibrancy and appears flat or "dull." This often causes exciting flavor notes to be lost, especially in lighter roasts.
Conversely, a KH value that is too low can lead to an overemphasis on acidity. The coffee then quickly tastes sharp, unbalanced, or unstable in its extraction.
Carbonate hardness is therefore a decisive factor for balance and clarity in taste.
Depending on the preparation method, the ideal water values differ slightly. This is because different brewing methods react differently to minerals.
For espresso, a carbonate hardness in the medium range is recommended, as balance and body are particularly important here. For filter coffee or pour over, on the other hand, the carbonate hardness should be lower to better highlight clarity and acidity structure.
Typical target ranges are:
These values provide a good guide for balanced taste and stable extraction.
Both water that is too hard and water that is too soft can negatively affect the coffee.
Water that is too hard contains too many minerals. While this does extract many substances, it often extracts the wrong ones. The result is a bitter, heavy taste. In addition, limescale builds up more quickly in the machine, which impacts maintenance and service life.
Water that is too soft, on the other hand, lacks the minerals needed to effectively dissolve aromas. The coffee then tastes thin, flat, and often acidic. The extraction is unstable and difficult to reproduce.
The goal is therefore always a balanced water profile – not as hard or as soft as possible.
If your water is not in the optimal range, it can usually be adjusted relatively easily.
One of the most common methods is the use of water filters. These specifically reduce hardness while simultaneously improving taste and machine compatibility.
Another option is water blending. By combining tap water with softer or mineralized water, values can be adjusted very precisely.
For advanced users and professional applications, there is also the option of specifically mineralizing water. In this process, individual minerals are added in defined amounts to achieve an optimal profile.
Water hardness has a direct impact on extraction and therefore on the taste in the cup. It determines which aroma compounds are dissolved and how they are perceived.
An excessively high carbonate hardness (KH) value, for example, can cause an espresso to taste flat and lackluster. An excessively low general hardness (GH) value can cause filter coffee to appear thin and under-extracted.
Optimized water, on the other hand, ensures clarity, balance, and consistency – two decisive factors for good coffee.
Beyond taste, water also plays an important role in the lifespan of your coffee machine. Water that is too hard leads to limescale deposits, which not only impair performance but can also cause long-term damage.
While regular descaling helps, it is not a sustainable solution if the water quality is permanently unsuitable. It is better to adjust the water directly to reduce limescale formation.
This not only saves on maintenance costs but also ensures more consistent coffee quality in your daily routine.
Water hardness is one of the most important, yet often overlooked, factors in coffee preparation. With the right levels, taste, extraction, and machine performance can be significantly improved.
Even small adjustments can make a big difference. That is why it is worth knowing your own water values and optimizing them accordingly.
