How to calculate the water footprint of a product or activity

The water footprint of a product is the total volume of freshwater used to make it, taking into account its entire value chain and not just the water you see inside the factory. Measuring it lets a company know where it consumes water, how much, and with what impact, and it is the foundation for cutting that consumption and managing the risk linked to scarcity.

There are two main approaches to calculating it: the volumetric method of the Water Footprint Network (how much water) and the impact-oriented approach of the ISO 14046 standard, based on life cycle assessment (what effect that water has depending on where and when it is used). This guide covers both, the calculation steps, and the tools available.

What is the water footprint of a product?

The water footprint measures the freshwater used across the life cycle of a good or activity. It includes water consumed directly and the virtual water embedded in upstream stages (raw materials, energy, inputs). The methodology developed by Arjen Hoekstra and the Water Footprint Network splits it into three components:

• Blue water footprint: surface or groundwater (rivers, lakes, aquifers) that is consumed, meaning it evaporates, is incorporated into the product, or does not return to the same basin.
• Green water footprint: rainwater stored in the soil and taken up by plants, particularly relevant in agriculture.
• Grey water footprint: the volume of freshwater needed to dilute the pollutants discharged until they meet environmental quality standards.

The sum of the three gives the total water footprint, expressed as a volume per unit of product (for example, litres or cubic metres per kilogram or per unit).

Two approaches: volumetric (WFN) and impact (ISO 14046)

Before calculating, it is worth deciding which question you want to answer, because there are two distinct and complementary frameworks:

The volumetric method is intuitive and useful for understanding the scale of consumption. However, a litre consumed in a basin with abundant water does not have the same impact as a litre in an area under water stress. That is why ISO 14046 weights consumption according to water availability in the basin, usually with the AWARE method, and delivers impact-oriented results that are better suited to corporate reporting.

How do you calculate the water footprint of a product? Step by step

Both the volumetric and the impact approach share a calculation structure based on the product life cycle.

1. Define the scope and the functional unit

You need to set out what will be assessed (a product, a batch, an activity), the stages included, and the reference unit (for example, 1 kg of product or 1 litre of beverage). Whether the results are comparable depends on this.

2. Identify the life cycle stages

Through a life cycle assessment, you map the phases where water is used:

• Raw-material production: water to grow or extract the base materials.
• Processing and manufacturing: process water, cleaning, cooling, and the water incorporated into the product.
• Supply chain and energy: water associated with electricity, transport, and purchased inputs.
• Use and end of life: water consumed during use (for example, appliances) and in waste management.

3. Collect data and measure the water at each stage

You quantify the volume consumed in each phase, distinguishing blue, green, and grey water. The usual sources are meters and bills for direct water, crop and climate data for green water, and pollutant-load and discharge-regulation data for grey water. Where primary data is missing, you draw on recognised databases.

4. Calculate the total footprint and, where relevant, the impact

You add up the components by stage to obtain the volumetric footprint. If you follow ISO 14046, you apply characterisation factors (such as AWARE) to translate the volume into impact weighted by the scarcity of each basin. The result is expressed in consistent units (litres or m³ per functional unit, or m³ equivalents in the case of impact).

Factors that influence the water footprint

• Type of crop or raw material: crops such as rice or cotton tend to have high water footprints because of their intensive water use.
• Geographic location: in arid areas or those facing water scarcity, the same process requires and affects the resource more.
• Production technology: more efficient processes and water reuse reduce the footprint.
• Water-management practices: efficient irrigation and effluent treatment lower the blue and grey components.

Why calculate the water footprint of a product?

Improve sustainability and efficiency

Knowing where consumption is concentrated lets you prioritise improvements, reduce operating costs, and strengthen corporate sustainability.

Respond to regulation and reporting

Water is gaining weight in sustainability reporting frameworks. The European standard ESRS E3 (water and marine resources), within the CSRD, requires companies in scope to report on water consumption and dependency, so having figures calculated with a sound method makes compliance easier.

Manage water risk

Pinpointing the points of highest consumption helps anticipate water risk in stressed areas and protect operational continuity.

Respond to customers and the market

More and more customers and consumers value the environmental information of products, so communicating the water footprint rigorously improves competitiveness.

Tools to calculate the water footprint

• Reference databases: the Water Footprint Network publishes water footprint estimates for many products and crops, useful when primary data is missing.
• Online calculator: Manglai's water footprint calculator lets you quickly estimate the footprint of products or activities.
• Specialised software: for auditable calculations and reporting in line with ISO 14046 or ESRS, it is worth using software that integrates activity data and calculation factors.

If you want to go deeper into how to reduce consumption, see our guide to strategies to reduce a company's water footprint.

Frequently asked questions about the water footprint of a product

What is the difference between the Water Footprint Network method and ISO 14046?

The Water Footprint Network measures the volume of water consumed (blue, green, and grey), while ISO 14046 assesses the environmental impact of that consumption through life cycle assessment, weighting it according to the scarcity of each basin. They are complementary approaches.

Which industries have the highest water footprint?

Water-intensive activities, such as agriculture (especially rice and cotton), the textile industry, and food and beverage production, tend to have the highest footprints. Globally, agriculture accounts for around 70% of freshwater withdrawals according to the FAO.

How can I reduce the water footprint of my product?

Through efficient irrigation and water reuse, improvements in production processes, selecting lower-footprint raw materials, and treating discharges to reduce the grey component.

To measure and manage the water in your products with a sound method and auditable data, discover Manglai's water footprint module.