Laundry Detergent Calculator
Enter your load size, how dirty the wash is, and your water hardness. The calculator gives a right-sized dose in millilitres, the powder equivalent, and what that dose costs per year at your detergent price.
Detergent packs print tables that flatter their sales. The honest dose is smaller than most people pour: excess surfactant does not clean better - it deposits on fibres, stiffens towels and feeds the mould behind that washed-but-smelly machine.
How to use
- Check your machine's rated drum size and weigh or estimate a typical load (a full drum of dry clothes runs 4-6 kg for most households).
- Find your water hardness from your water supplier's website - it changes the dose by up to 25%.
- Dose to the figure, run a wash, and adjust once: clothes smelling of nothing is the target, not a perfume cloud.
Frequently asked questions
How much detergent should I really use?
An 8 kg drum at normal soil and medium hardness takes about 50 ml of liquid or a 25-30 g powder scoop. Light washes in soft water run under 40 ml; hard water and sports kit push 65-80 ml. Most people pour one and a half to two times these figures.
What happens if I use too much detergent?
The surplus cannot rinse out: it coats fibres as a grey or stiff film, makes towels water-repellent and crunchy, traps odour, and feeds the biofilm that makes machines smell. It also fades colours faster - the classic signs are suds in the rinse and clothes that feel slick when wet.
Does water hardness change the dose?
Yes - hardness minerals deactivate part of the surfactant, so hard water needs about 25% more and soft water needs 15% less. Soft-water households that keep the packet's default dose are the most overdosed group there is.
Are detergent pods correctly dosed?
For full loads, roughly; pods are pre-measured for an average drum and cannot flex down for a half load, so small washes come out over-dosed. Two pods for a big or dirty load is fine - three is marketing.