Home & DIY
How much laundry detergent should I use per load?
Detergent grams per wash from load weight and water hardness — plus optional softener and yearly cost.
Quick answer
Dose in grams = the larger of two numbers: the minimum for your water hardness, or grams per kilo × the weight of the load.
Detergent per load
110 g
- Fabric softener (optional)
- ~25 ml
- Detergent per year
- 22.9 kg
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Dose = max(minimum, g/kg × load kg) from hardness — follow your product label if it differs. Hard water often needs more detergent and softener; a test strip beats guessing. Overdosing leaves residue and wastes money; underdosing on greasy loads may need a pre-wash boost.
How it works
| Water hardness | Per kg of laundry | Minimum per wash |
|---|---|---|
| Soft | ~18 g/kg | 45 g |
| Medium | ~22 g/kg | 55 g |
| Hard | ~28 g/kg | 70 g |
Worked example — a 5 kg load in medium water: 5 × 22 = 110 g per wash, which at four washes a week is about 23 kg of detergent a year. Hard water usually wants a softener as well (~25–40 ml). Always cross-check against the lines inside your own cap: concentrates need far less than economy jugs, and the cap is sized for the product in the bottle.
Overdosing is the silent budget leak: extra suds, residue on dark clothes, and wasted laundry detergent every week. Underdosing on greasy work clothes may need a second wash — doubling water and energy. Test hardness with strips once; city water companies often publish °f ranges online. Link to dryer running costs in our heat pump vs condenser comparison when you plan the full laundry bill.
The dose depends on a weight almost nobody measures. People fill the drum by eye and dose by how full it looks, but a load of towels weighs roughly twice the same drum filled with shirts — so the identical scoop is a double dose one week and half a dose the next. A usable rule without a scale: the drum is correctly loaded when a flat hand fits between the laundry and the top. One other choice worth making deliberately: powder contains a bleaching agent and outperforms liquid on whites and warm washes, while liquid handles grease and cold cycles better.
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Frequently asked questions
How does water hardness change detergent dose?+
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.
Liquid ml or powder grams?+
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.
Should I add softener every wash?+
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.
How much detergent cost per year?+
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.
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