Dose the detergent according to the manufacturer’s instructions on the back of the packaging. The instructions usually distinguish between how dirty your clothes are (lightly, moderately and heavily soiled) and water hardness. It is therefore advisable to sort the laundry according to how dirty the clothes are. As a rule of thumb, the dirtier the laundry, the higher the detergent dosage. This means that if the clothes are only a little bit dirty, use correspondingly less detergent. With regard to water hardness, the harder the water, the more lime it contains and the higher the detergent dosage (usually it already contains a descaler). The exact dosing quantities differ depending on the detergent. For example, a liquid detergent requires different quantities than a washing powder.
Important: Do not overdose the detergent! Too much detergent does not produce a better washing result but is expensive and at the same time harms the environment. As the detergent consumption increases, so does the water consumption of the washing machine, because too much detergent creates more foam and additional rounds of rinsing with clear water becomes necessary. Overdosing can also result in detergent residues in the washing machine detergent drawer. Therefore: Dose detergent according to the manufacturer’s instructions.
A little tip: Measuring cups for powder detergents are available free of charge at some drugstores (in Germany) or on the manufacturer’s website. Just have a look or ask.