Laundry Detergent Cost Calculator

How this is calculated

⛔ THIS TOOL DOES NOT TELL YOU HOW MUCH DETERGENT TO USE. The correct dose is printed on your own bottle, adjusted for your load size, your water hardness and how soiled the washing is - and it differs between products by a factor of two or more, because concentrations differ. Published dosing advice online contradicts itself badly: figures for the same situation vary between roughly 35 ml and 100 ml, and adjustment factors for hard water are variously given as 10%, 20%, 30% and 40% more. There is no honest number for this page to assert, so it asks for yours. WHAT IT DOES INSTEAD IS COST THE GAP between the dose on the label and the dose you actually pour, because that gap is usually large, entirely invisible, and paid for every single wash. ⚠️ THE CAP IS NOT A DOSE. On many products the cap holds substantially more than the recommended amount for a normal load, and filling it is the default behaviour for most people because nothing on the bottle stops you. Pour to the line, not to the brim. If your cap has no line, measure the recommended dose once with a kitchen measuring jug and mark the cap - it takes a minute and it applies to every wash you will ever run with that product. OVERDOSING IS NOT HARMLESS, WHICH IS WHY THIS IS WORTH KNOWING BEYOND THE MONEY. Excess detergent does not rinse out fully. It leaves residue in fabric, which stiffens it and can irritate skin, and it builds up inside the machine, which is a common cause of smells. More detergent is not more cleaning past the point the label specifies - the surfactants are already sufficient - so the extra is simply spent and then partly left behind. WATER HARDNESS AND LOAD SIZE GENUINELY DO CHANGE THE RIGHT DOSE. Hard water needs more, a half load needs less. Your bottle's own guidance covers both, and your water supplier publishes your hardness figure. Use those, then enter the resulting dose here. CONCENTRATED PRODUCTS ARE NOT COMPARABLE BY BOTTLE PRICE. A smaller bottle of a concentrate can be cheaper per wash than a large bottle of a dilute product, and the shelf price tells you nothing about which. Cost per wash is the comparison, and running two products through this tool is the way to make it. PODS ARE A FIXED DOSE and cannot be adjusted, which is a genuine trade-off rather than a flaw: they remove the overdosing problem entirely and remove your ability to dose down for a small load. To cost them, enter the number of pods per pack as the bottle volume and 1 as both doses.

Common questions

How much detergent should I actually use?

Whatever your own bottle says for your load size and water hardness - and this tool deliberately will not guess, because there is no honest single answer. Concentrations differ between products by a factor of two or more, so a dose that is correct for one bottle is a serious overdose or underdose for another. Published advice online is worse than unhelpful here: 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 label is the manufacturer's own figure for their own product, and your water supplier publishes your hardness.

Why does it ask what I actually pour?

Because for most people it is not the same as the label dose, and the difference is invisible and paid for every wash. The cap on many products holds substantially more than a normal-load dose, filling it is the default behaviour, and nothing on the bottle interrupts that. Measuring what your cap actually holds - once, with a kitchen measuring jug - is usually the moment people discover they have been using half again as much as intended for years.

Is using extra detergent actually a problem?

Yes, in two ways beyond the money. Excess detergent does not rinse out fully: it leaves residue in fabric, which stiffens it over time and can irritate skin, and it builds up inside the machine, where it is a common cause of persistent smells. And it does not clean better - past the dose the label specifies the surfactants are already sufficient for the soil in the load, so the extra is simply spent and then partly left behind in the clothes and the drum. If you are going to be wrong in one direction, slightly under the label is the better one.

How do I mark my cap?

Measure the recommended dose once in a kitchen measuring jug, pour it into the cap, and mark the level with a permanent marker or a scratch. That takes about a minute and then applies to every wash you run with that product for as long as you buy it. It is worth redoing when you switch products, because both the cap size and the recommended dose change. If your cap already has moulded lines, check which line corresponds to which load size - they are often unlabelled and easy to misread.

How do I compare two products?

On cost per wash, never on bottle price. A smaller bottle of a concentrated detergent can easily be cheaper per wash than a large bottle of a dilute one, and the shelf price gives you no way to tell - which is precisely why concentrates are packaged the way they are. Run each product through this tool with its own bottle size, its own price and its own recommended dose, and compare the cost-per-wash figures. That comparison also survives promotions, which bottle prices do not.

Does this work for pods?

Yes, with one substitution: enter the number of pods in the pack as the bottle size, and 1 as both doses. The cost per wash then comes out directly. Pods are a genuine trade-off rather than a better or worse choice - they eliminate the overdosing problem completely, because you cannot pour a pod generously, and 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.

What about water hardness and load size?

Both genuinely change the correct dose - hard water needs more because the minerals bind to the surfactants and reduce their cleaning power, and a half load needs less. Your bottle's own guidance covers both situations, and your water supplier publishes the hardness figure for your area, usually on their website by postcode or zip code. Work out the right dose from those two authorities, then enter the result here. This tool costs the dose; it does not choose it.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Laundry Detergent Cost Calculator at https://www.bfcbrilliance.com/tools/laundry-detergent-dosing-calculator.

What I entered:
- Bottle size (ml): ___
- Bottle price ($): ___
- Dose your bottle specifies (ml): ___
- Dose you actually pour (ml): ___
- Washes per week (washes): ___

What it calculated:
- Extra spent per year by over-pouring: ___
- Cost per wash at the label dose: ___
- Cost per wash at your dose: ___
- Washes per bottle at the label dose: ___
- Washes per bottle at your dose: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

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