There is no fixed dosage for this product, as the ideal amount depends on the size of your bathtub, your personal preference for scent and mineral concentration, and whether you're using it for a full-body soak or a smaller foot bath. As a general starting point, for a standard-sized tub filled to a comfortable level for bathing, many people use between 2 to 5 tablespoons (approximately 30 to 75 grams) of the bath salt, which corresponds to a portion of the 500g bag.
For a more subtle mineral and lavender aroma, or for a smaller bath (like a Japanese-style soaking tub), you might start with 1 to 2 tablespoons. For a more immersive experience or in a large, deep tub, you could increase the amount to 4-5 tablespoons. For a concentrated foot bath, 1 to 2 tablespoons in a basin of warm water is often sufficient. The sea salt will dissolve completely, leaving the water clear.
The most practical approach is to begin with a smaller amount, dissolve it in the running water, and see how the scent and feel meet your expectations. You can always add a bit more in subsequent baths. If you have sensitive skin or are cautious about fragrance, it is wise to start on the lower end of this range to assess your skin's reaction.