Show the formula and working
This free laundry detergent dose calculator scales the dose printed on your detergent pack to the real weight of your wash, for households in the UK, Ireland and Europe using liquid, powder or capsules. It also shows how many washes a pack gives and what each wash costs, so you can compare products fairly.
Quick answer: Packs give a dose for a standard 4.5 kg load at your water hardness. Multiply that dose by your load weight and divide by 4.5. With an example label dose of 35 ml, a laundry detergent dose calculator gives about 47 ml for a 6 kg load. Never exceed the largest dose printed on the pack.
What Is a Laundry Detergent Dose Calculator?
A laundry detergent dose calculator is a tool that adjusts the manufacturer’s dose to the weight of laundry you are actually washing. In plain words: your dose = the pack dose x your load in kg / the load the pack dose is for. Washes per pack = pack size / your dose, and cost per wash = pack price / washes per pack.
The starting point is the pack itself. Under Annex VII of the Detergents Regulation (EC) No 648/2004, consumer laundry detergents must state dosing for a standard washing machine load of 4.5 kg of dry fabric, or 2.5 kg for light duty detergents, for soft, medium and hard water. The dosing table on the pack is always the first authority; this tool simply scales it.
How Do You Use the Laundry Detergent Dose Calculator?
- Choose the Detergent type and How dirty is the load.
- From the dosing table on the pack, for your water hardness, enter the Label dose for a normal load (ml, g or pods) and the Label dose for a heavily soiled load (ml, g or pods).
- Check the Load size the label dose is for: 4.5 kg for most detergents, 2.5 kg for delicate ones.
- Enter Your load (dry weight) in kg.
- For cost per wash, enter the Pack size (ml, g or pods) and the Pack price.
- Read the dose, then open “Show the formula and working” to see the scaling, washes per pack and cost per wash.
How Much Detergent Should I Use Per Load?
Use the dose on the pack for your water hardness and soil level, scaled to your load: for a 4.5 kg load, use exactly the pack dose; for 9 kg, about twice as much, up to the largest dose the pack allows. Soft water needs less detergent than hard water, and lightly worn clothes need less than heavily soiled ones. Too little leaves dirt behind, and too much wastes money and can leave residue on clothes and in the machine.
| Load (dry weight) | Share of 4.5 kg standard load | Dose with a 35 ml pack dose | Dose with a 75 g pack dose |
|---|---|---|---|
| 2 kg | 44% | 15.6 ml | 33 g |
| 3 kg | 67% | 23.3 ml | 50 g |
| 4.5 kg | 100% | 35 ml | 75 g |
| 6 kg | 133% | 46.7 ml | 100 g |
| 7 kg | 156% | 54.4 ml | 117 g |
| 8 kg | 178% | 62.2 ml | 133 g |
| 9 kg | 200% | 70 ml | 150 g |
The 35 ml and 75 g pack doses are examples only. Enter the figures from your own pack, and stay within its maximum dose.
Does Water Hardness Change the Detergent Dose?
Yes: hard water needs more detergent than soft water, which is why every pack gives separate doses for soft, medium and hard water. Minerals in hard water tie up part of the detergent. Your water supplier publishes the hardness for your postcode, often in mg/l as calcium carbonate. As a guide to the units, 1 mmol/l equals 100 mg/l as calcium carbonate, and one German degree (°dH) is about 17.8 mg/l, according to the hard water article on Wikipedia.
How Do I Know the Weight of My Washing?
The easiest way is to weigh it: stand on bathroom scales holding the basket of dry laundry, then subtract your own weight and the basket. A full drum loaded loosely for a cotton wash is close to the machine’s rated capacity, so a half full 8 kg machine holds about 4 kg. Detergent is only part of the cost of a wash, and the washing machine running cost calculator adds the electricity.
Worked Example: Dosing a 6 kg Wash
Example: a 1 litre bottle of liquid detergent costs £6, and its dosing table says 35 ml for a normally soiled 4.5 kg load in your water hardness. You are washing 6 kg of normally soiled clothes. The dose is 35 x 6 / 4.5 = 46.7 ml, shown rounded as 47 ml. At that dose the bottle gives 1,000 / 46.7 = 21.4 washes, and each wash costs £6 / 21.4 = 28p.
Capsules cannot be split, so the calculator rounds to whole pods and works out the cost from the pod count. Store capsules and all detergents out of reach of children, and never mix laundry products with bleach unless the label says it is safe; bleach must never be mixed with ammonia or acids. To finish the wash for less, compare drying costs with the tumble dryer running cost calculator, or browse the energy bill calculators.
Laundry Detergent Dose Calculator FAQs
How much liquid detergent do I use for a full load?
Use the pack dose for 4.5 kg, then scale it to your load. For an example pack dose of 35 ml, a 6 kg load needs about 47 ml and a 9 kg load about 70 ml, provided the pack allows that much.
What is a standard washing machine load?
Under the EU detergents rules kept in UK law, a standard load is 4.5 kg of dry fabric for normal detergents and 2.5 kg for light duty detergents for delicates. Pack dosing tables and “washes per pack” claims are based on these loads.
Can I use less detergent than the pack says?
Yes, for smaller loads, soft water or lightly worn clothes. Scale the dose to the load weight and choose the soft water figure if your supply is soft. If clothes come out dull or smelling, go back up to the pack dose.
How many pods should I use?
Follow the pack, which usually gives one pod for a normal load and more for large, heavily soiled or hard water washes. Put pods in the empty drum before the clothes, and never cut or split them.
What happens if I use too much detergent?
Too much detergent can cause oversudsing, leave a sticky residue on clothes and build up in the drum and drawer, which can lead to smells. It also wastes money. Stick to the largest dose on the pack at most.
How do I work out the cost per wash?
Divide the pack size by your dose to get washes per pack, then divide the price by that number. A £6 litre of liquid used at 46.7 ml a wash gives 21.4 washes at 28p each.
Checked October 2026. Sources: Regulation (EC) No 648/2004 on detergents, Annex VII (legislation.gov.uk), Hard water (Wikipedia).