How much laundry detergent should I use per load?

Hard water binds detergent before it cleans fabric — you need more grams per kg and often fabric softener to prevent stiffness. Soft water needs less; using hard-water doses in soft areas leaves sticky residue. If you use a water softener for the whole house, treat water as soft in the calculator.

This tool outputs grams — for standard liquid, roughly 1 ml ≈ 1 g. Concentrated liquids may be 2–4× stronger per ml; follow the product cap, not a generic table. Pods are pre-dosed: use them only for the load size the manufacturer states.

Not mandatory — useful in hard water, towels and bedding for softness. Sportswear and microfibre often lose absorbency with softener. The calculator suggests ml only for medium/hard profiles; skip on loads that need wicking.

Grams per wash × washes per week × 52 ÷ 1000 = kg/year. Multiply by your price per kg (large bottles are cheaper per kg than small). A family at 110 g × 4/week × 52 ≈ 23 kg — at €3/kg that is ~€69/year before softener.