How much SILA liquid laundry soap should I use?

There is no fixed dosage because the right amount depends on the task, the level of soiling, and your water hardness. The source notes that harder water reduces how effectively soap works, so you may need to adjust the amount accordingly. As a general starting point, begin with a small amount and increase if needed. For hand-washing laundry or surfaces, add a teaspoon to a few tablespoons to a basin of water and see if it handles the grime. For machine laundry, add a few tablespoons for a full load and adjust based on the dirtiness of the clothes and your water hardness.

If you have hard water, you may need to use more soap or consider a water softener, as soap can form a film in hard water. For heavily soiled items, you can apply the soap directly to a sponge or pre-wash stains. It is better to start with less and add more, because using too much soap can leave residue that requires extra rinsing.