Cleaning Chemical Dilution Ratios Explained – Janitorial Depot

Reviewed by Janitorial Depot | 8 September 2026

Diluting a cleaning chemical should be simple, but the instructions are not always written the same way. You may see 1 in 20, 1:20, 20:1, 20mL per litre, a percentage, neat or ready to use.

The numbers can look similar and still mean different things. The safest rule is simple: read the words on the label or Product Data Sheet before you do the maths.

At Janitorial Depot, we also teach one basic mixing rule for manual dilution: water first, chemical second. Put the water in the clean bottle or bucket, then add the measured concentrate. Do not pour water onto a pool of concentrate.

Quick answer: If a manufacturer defines 1 in 20 as one part product in 20 total parts, a 500mL mix contains 25mL product. If 1:20 means one part product plus 20 parts water, there are 21 total parts. If a ratio does not say which side is product and which side is water, stop and check before mixing.

How to Dilute Cleaning Chemicals Correctly

Before you mix anything, check these points:

Product: make sure you have the right chemical.
Job: check the rate for the task you are doing.
Directions: use the label, PDS, technical bulletin or dosing chart for that product.
Wording: work out what the ratio actually describes.
Volume: check whether the stated amount is water volume or finished volume.
Safety: check the SDS before handling a hazardous concentrate and use the required PPE.

If the manufacturer gives an exact dose, such as 6mL per litre or a bottle measurement, use it. Do not convert a clear instruction into another ratio just because a calculator can.

Quick Guide to Common Cleaning Chemical Dilution Instructions

Instruction	What to do
1 in N	Check that N means the total finished volume. Product = finished volume ÷ N.
1 part product to N parts water	Add the parts together. Total parts = 1 + N.
X mL per 1L water	Use the stated product dose with the stated litre of water.
X mL, make up to 500mL	500mL is the final volume.
X% v/v	Volume per volume. Check that the percentage refers to the finished mix.
X% w/v or X% w/w	Do not treat these as a simple liquid-volume ratio.
Neat / undiluted	Do not add water for that use.
Ready to use / RTU	Use as supplied unless the label says otherwise.
10:1, 20:1 or another bare colon ratio	Check which number is product and which is water before calculating.

What Does a 1 in 20 Dilution Mean?

Where 1 in 20 means one part product in 20 total parts, divide the finished volume by 20.

For a 500mL bottle:

500mL ÷ 20 = 25mL product

That leaves about 475mL for water:

475mL water + 25mL product = 500mL

For 10L:

10,000mL ÷ 20 = 500mL product

Agar uses this final-volume approach in its dilution calculator and 2025 dilution chart. You can also browse our Agar cleaning chemicals.

Is 1:20 the Same as 1 in 20?

No, not in every case.

Australia's TGO 104 gives a clear example for liquid disinfectants within its scope. It defines:

1 in N: one part disinfectant made up to N total parts.
1:N: one part disinfectant added to N parts diluent.

Instruction	Total parts under TGO 104
1 in 20	20 total parts
1:20	1 part product + 20 parts diluent = 21 total parts

TGO 104 is a disinfectant standard, not a rule for every cleaner. For ordinary cleaners, use the wording supplied for that product. For disinfectants, follow the label and use conditions. See our commercial disinfectants and sanitisers.

How Do You Calculate 1 Part Chemical to 20 Parts Water?

If the instruction says 1 part product to 20 parts water, there are 21 parts altogether.

For exactly 1L:

1,000mL ÷ 21 = about 47.6mL product

Water is about 952.4mL.

952.4mL water + 47.6mL product = about 1L

Do not change this to 1 in 20. A 1 in 20 final-volume mix uses 50mL product per litre.

How Much Chemical Goes Into a 500mL Bottle at 1:20?

Only use this calculation if 1:20 has been defined as one part product to 20 parts water.

There are 21 parts:

500mL ÷ 21 = about 23.8mL product

Water is about 476.2mL.

476.2mL water + 23.8mL product = about 500mL

Compare that with 1 in 20, which uses 25mL product in a 500mL final mix.

What Does a 20:1 Dilution Mean?

20:1 means nothing useful until you know what each number stands for.

Some instructions put water first. Others put product first. Look for words such as 20 parts water to 1 part product or 1 part product to 20 parts water.

If the label or PDS does not say, do not guess.

What Does mL per Litre Mean?

If the manufacturer gives a dose in mL per litre, use that dose as written.

For example, Whiteley's Tempo HD technical bulletin gives 6mL per litre of water for spray-and-wipe cleaning.

That means:

1L water + 6mL Tempo HD

Other Tempo HD jobs use different doses. That is why you should check the task, not just the product name. Janitorial Depot stocks Whiteley Tempo HD and the wider Whiteley cleaning range.

What Does a Percentage Dilution Mean?

First ask what the percentage describes.

If a direction says 5% v/v final solution, 5% of the finished volume is liquid product. For 500mL:

500mL × 5 ÷ 100 = 25mL product

On the same volume basis, 1 in 20 is also 5%. A 1:20 product-to-water mix is different because it has 21 total parts. Its product share is about 4.76%.

% v/v, % w/v and % w/w Are Not the Same Thing

% v/v means volume per volume.
% w/v means weight per volume.
% w/w means weight per weight.

Do not swap one for another. If the instruction is % w/v or % w/w, use the manufacturer's dosing information rather than trying to turn it into mL by guesswork.

A Percentage on the Product Is Not Necessarily the Dilution Rate

A percentage can describe the strength of the product in the container, not the mix you should make.

Agar Bleach 5% Available Chlorine is a good example. Agar's Bleach PDS says it contains 5% available chlorine when packed. That does not mean every job uses a 5% bleach dilution.

Always check what the percentage refers to.

What if the Directions Say 25mL Product per 500mL Water?

If the instruction says 25mL product per 500mL water, use 500mL of water and add 25mL product. The result is about 525mL.

If it says 25mL product, make up to 500mL, the final volume is 500mL.

Those are different instructions. Read the words, not just the numbers.

Why the Same Cleaning Chemical Can Have Several Dilution Ratios

One product can have several rates because different jobs need different strengths.

Agar's Dirt-Off PDS gives:

Light soilage: 1 in 80
Heavy kitchen fat removal: neat
General heavy-duty cleaning: 1 in 20
Spray-and-wipe cleaning: 1 in 30
Floor scrubbing: 1 in 80
Pressure washing: 1 in 120

So there is no single "Dirt-Off dilution". The right rate depends on the job. The same rule applies across our floor cleaning solutions and other concentrates.

Different Cleaning Chemical Brands Can Use Different Formats

Across the brands we supply, you will see more than one way of writing dilution instructions.

Agar often uses 1 in N. Whiteley uses direct mL/L doses on products such as Tempo HD. Some products use colon ratios, percentages, fixed bottle doses or ready-to-use directions.

We do not teach one rule for an entire brand. We check the exact product and the exact job. You can also browse our Research Products cleaning chemicals.

A Real Example of Why an Isolated Ratio Can Be Ambiguous

Enzyme Wizard's Heavy Duty Floor/Surface Cleaner lists 10:1 for general cleaning and 50:1 for heavy-duty cleaning.

Those numbers do not tell you, by themselves, which side is water.

If the label or data sheet does not spell it out, stop and check with us or the manufacturer before mixing. Do not let a calculator make that decision for you.

Do You Add Water or Chemical First?

Water first. Chemical second.

At Janitorial Depot, this is the practical rule we teach for manual dilution. Put the water in the bottle or bucket first. Then add the measured concentrate slowly.

Why? Pouring water onto concentrate can make some cleaners foam quickly. The foam can rise up the container and carry chemical onto your hands or towards your face. Starting with water gives the concentrate room to disperse and makes the fill easier to control.

Agar's dispenser-bottle training also says water first, then the chemical dose. For hazardous products, wear the PPE listed in the SDS before you start.

If you use a closed dosing or dispensing system, follow that system's instructions.

What PPE Is Required When Diluting Cleaning Chemicals?

There is no single PPE set for every chemical.

Check the SDS before you open or pour a hazardous concentrate. The SDS tells you what protection is required for that product.

WorkSafe Victoria also recommends controls that reduce contact with concentrate, such as automatic dilution units, pouring devices and splash prevention. PPE is part of the control system, not the whole system.

PDS vs SDS: Which Document Gives the Dilution?

Product label, PDS or technical bulletin

Use these for the practical directions: what the product is for, how much to use, where to use it, and any task-specific rinse or contact instructions.

Safety Data Sheet

Use the SDS for hazards, PPE, first aid, storage, handling and spill information. WorkSafe Victoria explains the role of the SDS in its Safety Data Sheets guidance.

In short: use the label or PDS for the dose, and the SDS for safe handling.

What Victorian Workplace Requirements Matter?

Victoria does not use one universal ratio format for every ordinary cleaner.

WorkSafe Victoria focuses on controlling hazardous substances, training workers, keeping SDSs available and making sure containers are identified. For higher-risk chemicals, it also points to controls such as automatic dilution and splash prevention.

The federal TGO 104 rules discussed above apply to relevant disinfectants. For other cleaners, follow the product directions and Victorian workplace safety requirements.

Do Diluted Cleaning Chemicals in Spray Bottles Need Labels?

Do not leave a hazardous chemical in an unmarked bottle.

WorkSafe Victoria warns that unlabelled liquids can be mistaken for water or another harmless product. Workplace containers need to be clearly marked or labelled so people can identify what is inside.

You can also add practical site information, such as the task or dilution, where it helps your team. Do not treat those extra details as a legal requirement unless the rule for that product or workplace says so.

What Do Neat, Undiluted and Ready to Use Mean?

Neat or undiluted

Use the product without adding water for that task.

Ready to use

Use the product as supplied. Do not dilute it unless the label says you can.

Does More Cleaning Chemical Make It Work Better?

No. More is not better.

Too much concentrate wastes chemical and can increase foam, residue and exposure. Use the rate given for the job.

For disinfectants, do not change the labelled concentration. TGO 104 ties performance testing to the dilution recommended on the label for that use.

Never Mix Different Cleaning Chemicals Unless Specifically Directed

Diluting a product with water is not the same as mixing two chemicals together.

Do not combine cleaners unless the manufacturer tells you to. Agar's Bleach PDS, for example, warns never to mix bleach with other chemicals, especially acids.

Also avoid topping up a bottle that still contains old solution. Agar's dispenser training says to use the solution, wash the bottle, then refill it.

Why a Generic Chemical Dilution Calculator Can Give the Wrong Answer

A calculator can do the maths. It cannot read the label for you.

If you enter 1:20 as one part product to 20 parts water, the calculator will use 21 total parts. If the instruction actually means 1 in 20 final volume, you will get the wrong dose.

The same problem applies to 10:1, 20:1, 50:1 and percentages that do not say whether they are v/v, w/v, w/w or active-ingredient strength.

Read first. Calculate second.

Common Cleaning Chemical Dilution Mistakes

Treating 1 in 20 and 1:20 as the same instruction
Guessing which side of a colon ratio is water
Confusing water volume with final volume
Treating an active-ingredient percentage as a mixing rate
Mixing up % v/v, % w/v and % w/w
Ignoring a clear mL/L dose and converting it into another ratio
Putting concentrate in an empty bottle, then pouring water onto it
Using one rate for every job
Using more chemical because it seems stronger
Diluting a ready-to-use product
Mixing different cleaners
Topping up old solution
Using old product directions

Cleaning Chemical Dilution FAQ

What does 1 in 20 dilution mean?

If it means one part product in 20 total parts, divide the final volume by 20. For 500mL, that is 25mL product and about 475mL water.

How much chemical do I use per litre at 1 in 20?

For a final-volume 1 in 20 mix, use 50mL product in 1L finished solution.

Is 1:20 the same as 1 in 20?

Not always. TGO 104 defines them differently for relevant liquid disinfectants. For other products, read the wording on the label or PDS.

What percentage is a 1 in 20 dilution?

On a simple volume basis, one part in 20 total parts is 5%. Only call it 5% v/v where volume per volume is the correct basis.

Is 1:20 equal to 5%?

Not if 1:20 means one part product plus 20 parts water. That is 21 total parts, so the product share is about 4.76% on a simple volume basis.

Does 5% on a chemical label mean I should dilute it to 5%?

No. The 5% may describe the product as supplied, such as 5% available chlorine, rather than the working dilution.

What is the difference between % v/v, % w/v and % w/w?

% v/v is volume per volume. % w/v is weight per volume. % w/w is weight per weight. Do not swap them.

What does 20:1 dilution mean?

It depends on what the manufacturer says each number represents. If that is not clear, check before mixing.

What does 20mL per litre mean?

If the direction says 20mL per 1L of water, use 20mL product with that 1L of water. If it says make up to 1L, then 1L is the final volume.

Do I put water or chemical in the bottle first?

Water first, then chemical. Put the water in the clean container, then add the measured concentrate.

Why does the water go in first?

Pouring water onto concentrate can make some cleaners foam quickly. That foam can rise out of the container and carry chemical onto your hands or towards your face. Water first gives you a more controlled mix.

What PPE should I wear when diluting cleaning chemicals?

Use the PPE listed in the SDS for that product. The right gloves, eye protection or clothing depend on the chemical you are handling.

Can the same cleaning chemical have several dilution ratios?

Yes. The rate can change with the job, soil level and application method. Dirt-Off is one example.

Should I use the PDS or SDS for dilution?

Use the label, PDS or technical bulletin for the dose. Use the SDS for hazards, PPE and safe handling.

Can I use a generic cleaning chemical dilution chart?

Yes, but only after you know what the manufacturer's ratio means. A chart should never overrule the product directions.

Can I use the same dilution for cleaning and disinfecting?

Only if the label says so. Cleaning and disinfecting may use different rates, contact times and rinse instructions.

Does stronger cleaning chemical work better?

No. Use the rate specified for the task. More concentrate can waste product and create extra foam, residue or exposure.

What should I do if the dilution ratio is unclear?

Do not guess. Check the label, PDS, technical bulletin or dosing chart. If it is still unclear, ask Janitorial Depot or the manufacturer before mixing.

Understand the Dilution Before You Do the Maths

You do not need to memorise every ratio. You need to read the instruction correctly.

Check the product, the task and the wording. Work out whether the number refers to final volume, water volume, parts, mL/L, a percentage or the strength of the concentrate. Check the SDS when you are handling a hazardous product.

Then mix it properly: water first, chemical second.

If you are unsure, ask us before you mix it. We can help you check the product directions and choose the right commercial cleaning chemical for the job.