What is COSHH and why does dilution matter?

COSHH stands for Control of Substances Hazardous to Health. It is a UK regulation requiring employers to control exposure to hazardous substances. Correct dilution ensures chemicals are effective without being dangerously strong. Over-concentrating wastes product, increases health risk and can damage surfaces. Under-diluting means the solution will not clean or disinfect effectively.

How do I read a dilution ratio?

A dilution ratio like 1:50 means 1 part concentrate to 50 parts water. For a 5-litre bucket at 1:50, you would add approximately 98 ml of concentrate and fill the rest with water. Always add concentrate to water, not the other way round, to reduce splashing.

What dilution is needed for food contact surfaces?

Food contact surfaces typically require a weaker dilution (around 1:100) to ensure no harmful residue remains. The solution must still achieve the necessary antimicrobial activity. Always check the manufacturer data sheet for the specific product approved dilution rate.

What PPE is needed when diluting chemicals?

At minimum, wear chemical-resistant gloves and eye protection when handling concentrates. For strong concentrates or large volumes, add an apron and consider a face shield. Always work in a well-ventilated area. Check the COSHH data sheet for product-specific PPE requirements.

CleanCalcs

COSHH Dilution Calculator

Calculate correct dilution ratios for cleaning chemicals based on concentration and application type.

Application

What surface or area is being cleaned?

Container Size

Volume of your mixing container

Concentrate Strength

Strength of the concentrate (100% = neat)

How We Calculate This

This calculator determines the correct volume of concentrate and water needed for your chosen container size and dilution ratio.

The formula

Concentrate (ml) = Container size / (Dilution ratio + 1)

Water (ml) = Container size - Concentrate

Concentration adjustment

If your concentrate is not 100% strength (e.g. a pre-diluted product at 50%), the calculator adjusts the ratio accordingly so you get the correct final strength.

Recommended ratios

General cleaning: 1:50
Food-safe: 1:100
Washroom: 1:25
Floor mopping: 1:40
Heavy degreasing: 1:10

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always verify quantities and timings for your specific situation.