Nearly every household uses more laundry detergent than it needs. The dose printed on the bottle assumes a medium load, average soil and moderately hard water — change any of those three and the right amount changes with it.
This calculator adjusts the manufacturer’s stated dose for your actual conditions. It is a starting point, not a rule: confirm it with the suds check underneath.
Check the result against your machine
The calculator gets you close. These two tests tell you whether it is actually right for your water, your detergent and your machine.
The suds check
Look through the door mid-wash. You want a thin ring of suds, not a window full of foam. Heavy foam means you are still over-dosing — drop another 20% and check again.
The rinse check
Take a clean dry towel from the wash and rub it hard between your hands over a dark surface. If you see foam, or a wet patch goes cloudy when squeezed, detergent is still in the fibres.
To reset a wardrobe that has years of residue in it, run everything through a full cycle with no detergent at all, on the hottest temperature the fabric allows. Two such washes is usually enough before towels feel absorbent again.
Things the calculator does not cover
- Pods and capsules are a fixed dose. If your result is under about 70%, a pod is too much for that load — use liquid or powder instead, or add more laundry.
- Machines with auto-dosing reservoirs handle this themselves. Set the reservoir to your water hardness and leave it alone.
- Non-HE detergent in an HE machine will over-suds whatever the dose. Check the packet for the HE symbol.
- Fabric softener is not detergent and this does not apply to it. On towels and activewear, the right amount is none.
The reasoning behind all of this — why excess detergent causes stiff towels, grey whites and a machine that smells — is in How Much Laundry Detergent You Actually Need. If your whites have already gone grey, start with Hard Water and Laundry.