How Dilution Ratios Work
A dilution ratio expresses how much concentrate to mix with how much water (or other diluent) to reach a usable strength. It is written as concentrate to water, such as 1:10, meaning 1 part concentrate combined with 10 parts water. Ratios are used everywhere a concentrated product needs weakening before use, including cleaning chemicals, disinfectants, garden and lawn treatments, agricultural sprays, cordial, and laboratory reagents. Unlike the C1V1 = C2V2 formula used for molar solution chemistry, a dilution ratio works in simple parts, so it does not require you to know the exact concentration of the stock, only the ratio recommended by the manufacturer.
Two Ratio Conventions
There are two common ways manufacturers express a ratio, and mixing up which one applies to your product can significantly change the strength of your mix.
| Convention | Meaning of 1:10 | Total Parts | Concentrate % |
|---|
| Parts of water added | 1 part concentrate + 10 parts water | 11 | 9.09% |
| Total parts in the mix | 1 part concentrate in 10 total parts (9 parts water) | 10 | 10.00% |
Most cleaning and horticultural products in New Zealand and Australia use the "parts of water added" convention, but always check the product label or safety data sheet (SDS) to confirm, since using the wrong convention can leave a mix too strong or too weak.
Working Out Concentrate and Water Volumes
Once you know the total parts in your ratio, divide your target total volume by the total parts to find the value of one part. Multiply that by the concentrate parts to get the concentrate volume, and by the water parts to get the water volume.
- Value per part = target total volume divided by total parts
- Concentrate volume = value per part multiplied by concentrate parts
- Water volume = target total volume minus concentrate volume
If you instead start from a fixed amount of concentrate (for example, you have 100 mL of concentrate and want to know how much water to add), multiply the concentrate volume by the water parts and divide by the concentrate parts to get the water volume needed.
Worked Example
For a 1:10 ratio (parts of water added convention) and a target total volume of 1000 mL, there are 11 total parts (1 concentrate + 10 water). Each part is 1000 divided by 11, which is approximately 90.91 mL. The concentrate needed is 1 part, or 90.91 mL, and the water needed is 10 parts, or approximately 909.09 mL. This gives a mix strength of about 9.09% concentrate.
Common Dilution Ratios and Their Uses
- 1:4: heavy-duty degreasers and strong disinfectants
- 1:10: general-purpose cleaners and sanitisers
- 1:16 to 1:32: window cleaners, light-duty sprays, some garden chemicals
- 1:64 to 1:100: dilute lawn and garden feeds, some pool chemicals
- 1:128 and higher: very dilute agricultural and horticultural sprays
Always follow the manufacturer's recommended ratio on the product label or SDS. Using a stronger mix than recommended wastes concentrate and can damage surfaces, fabrics, or plants, while a weaker mix may not clean or treat effectively.
Frequently Asked Questions
What does a dilution ratio like 1:10 mean? It means 1 part concentrate to 10 parts water under the common convention, making 11 total parts. Some manufacturers instead mean 1 part concentrate in 10 total parts. Always check the label.
How do I convert a dilution ratio to a percentage? Divide the concentrate parts by the total parts and multiply by 100.
How much concentrate do I need for a specific bottle size? Divide your target total volume by the total parts, then multiply by the concentrate parts.
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Sources: Standard part-based dilution ratio arithmetic, as used in cleaning industry dilution charts and horticultural chemical labelling guidance. Worksafe New Zealand hazardous substance labelling requirements (worksafe.govt.nz).
This calculator provides general dilution ratio maths only. Always follow the specific mixing instructions, safety data sheet (SDS), and personal protective equipment guidance for the product you are using. Some products specify their ratio using a different convention to the ones shown here, so confirm against the label before mixing.
