How Much Laundry Detergent Are You Really Using?

This page won't tell you how much to use

And you should be suspicious of the ones that do.

Detergent concentrations differ between products by a factor of two or more, so a dose that's correct for one bottle is a serious overdose or underdose for another. Published advice online is worse than unhelpful — figures for the same situation range from about 35 ml to 100 ml, and hard-water adjustments are variously given as 10%, 20%, 30% and 40% more.

Your own bottle is the manufacturer's figure for their own product. Your water supplier publishes your hardness. Those are the two authorities.

What this calculates is the gap between the dose on your label and the dose you actually pour — because that gap is usually large, completely invisible, and paid for every single wash.

The cap is not a dose

On many products a full cap holds substantially more than a normal-load dose. Filling it is the default behaviour, because nothing on the bottle interrupts you.

At the defaults above — a 75 ml label dose, 110 ml actually poured, five washes a week — that's 47% over, and $72.80 a year in detergent that was never meant to go in.

The fix takes a minute:

1. Measure the recommended dose in a kitchen measuring jug
2. Pour it into the cap
3. Mark the level with a permanent marker

That mark then applies to every wash you run with that product. Redo it when you switch products, because both the cap size and the recommended dose change.

If your cap already has moulded lines, check which line means which load size — they're often unlabelled and easy to misread.

More isn't cleaner

The money is the least interesting part of overdosing.

Past the dose the label specifies, the surfactants are already sufficient for the soil in the load. The extra doesn't clean — it fails to rinse out. It leaves residue in fabric, which stiffens it over time and can irritate skin, and it builds up inside the machine, where it's a common cause of persistent smells.

So if you're going to be wrong in one direction, slightly under the label is the better one. How far over the label dose you are goes negative when you're dosing under, which is usually fine.

Compare products on cost per wash

Never on the bottle price.

A smaller bottle of a concentrate can easily be cheaper per wash than a large bottle of a dilute product, and the shelf price gives you no way to tell — which is exactly why concentrates are packaged the way they are.

Run each product through with its own bottle size, price and recommended dose, then compare Cost per wash at your dose. That comparison also survives promotions, which bottle prices don't.

Washes per bottle at your dose is often the first clue that something has drifted. If a bottle that should give you twenty washes is lasting fourteen, you already know the answer.

Pods

Enter the number of pods in the pack as the bottle size, and 1 as both doses. Cost per wash comes out directly — a 40-pod pack at $14 is $0.35 a wash.

Pods are a genuine trade-off rather than a better or worse choice. They eliminate overdosing completely, because you can't pour a pod generously. They also remove your ability to dose down for a small or lightly soiled load.

Whether that trade is worth it depends on how variable your washing is.

Hardness and load size do matter

Both genuinely change the correct dose. Hard water needs more, because the minerals bind to the surfactants and reduce their cleaning power. A half load needs less.

Your bottle's guidance covers both situations, and your water supplier publishes your area's hardness — usually searchable by postcode or zip code on their website.

Work the right dose out from those two, then enter the result here. This tool costs the dose. It doesn't choose it.