Water is 98% of your cup. Enter what's coming out of your tap and we will compare it with the clearly labelled starting bands below.
Comparison only. These readings do not certify drinking-water or equipment safety.
GH is total hardness, chiefly calcium and magnesium, expressed as ppm equivalent CaCO₃. KH test kits approximate alkalinity in the same reporting units. Neither is the same as TDS, and neither alone establishes potability, corrosion or scale risk.
This tool uses BrewLab starting comparison bands: GH 50–150 and alkalinity 40–70 ppm as CaCO₃. They match the accompanying article and are editorial starting points, not a current SCA standard or machine warranty requirement. Older tables giving calcium hardness must not be relabelled as total GH.
Worked blending example: assuming a low-mineral diluent reads GH 0/KH 0, equal volumes of potable water at GH 160/KH 80 and the diluent give approximately GH 80/KH 40. This is a weighted-average example, not a safety recommendation. A cartridge’s effect depends on its media, condition and water composition; remeasure rather than assuming any jug filter reduces both readings.
For an espresso machine, follow that model’s documented water limits and descaling instructions. See SCA’s current standards index; this independent home guide is not an SCA assessment.
Use potable water suitable for your brewer. Distilled water can be a blending ingredient, but machine compatibility and flavour need separate checks.
Some brands (Volvic-style low mineral) brew beautifully. Check the label for calcium and bicarbonate values.
Scale depends on hardness, alkalinity, temperature and the machine. Follow the manufacturer’s water and maintenance instructions rather than a universal monthly schedule.
High alkalinity can reduce perceived acidity, but chalkiness has several causes. Measure the water and compare a small controlled brew before changing it.