What Is a Life Cycle Assessment? A Complete Guide

A life cycle assessment (LCA) is a standardised, ISO-defined method for measuring the environmental impact of a product, service or system across its entire life — from raw material extraction, through manufacturing and use, to disposal or recycling. So what is a life cycle assessment in practice? It is a structured way to quantify impacts such as carbon emissions, water use and resource depletion at every stage, so a business can make credible environmental claims, win tenders, publish an Environmental Product Declaration or design better products on evidence rather than guesswork. This guide covers what an LCA measures, the four phases and standards behind it, the data it needs, and — as of mid-2026 — when a UK business actually needs one.

Key takeaways

• An LCA measures multiple environmental impacts across a product's whole life cycle, following the international standards ISO 14040 and ISO 14044.
• It runs in four phases: goal and scope definition, inventory analysis, impact assessment and interpretation — and the phases are iterative, not linear.
• A product carbon footprint is a narrower LCA that covers only greenhouse gases; an EPD is a verified, published summary of an LCA's results.
• No UK law forces most businesses to run an LCA, but customer requests, tenders, construction EPDs and a fast-tightening green-claims regime increasingly make one unavoidable.
• Being current matters: the carbon-footprint standards are being harmonised, background databases move fast, and green-claims enforcement now carries real financial risk.

What is a life cycle assessment, exactly?

The defining feature of an LCA is that it looks at the whole life cycle, not a single stage. A product that is cheap to run may be carbon-heavy to make; a "recyclable" material may carry a large water or land footprint upstream. By accounting for every stage, an LCA is designed to stop you solving one problem while quietly creating a larger one somewhere else in the chain — what practitioners call burden-shifting.

An LCA is also multi-criteria. Rather than reporting one number, a full assessment quantifies a set of environmental impact categories. Under the construction rules in EN 15804+A2, for example, an LCA reports climate change alongside acidification, eutrophication, ozone depletion, photochemical ozone formation, water use and resource depletion, among others. That breadth is what separates a full LCA from a single-issue metric like a carbon footprint — a distinction we come back to below.

Assessments are typically expressed against a functional unit — a defined quantity of the thing being studied, such as "one litre of paint covering ten square metres for ten years". The functional unit is what makes results comparable: two products only compare fairly if they deliver the same service.

What are the four stages of an LCA?

Every conformant LCA follows the four phases set out in ISO 14040:2006, the framework standard (amended in 2020). They are worth knowing because they map directly onto how a project actually runs.

1. Goal and scope definition. You decide why you are doing the study, what the functional unit is, and where the system boundary starts and stops. Get this wrong and everything downstream is measuring the wrong thing.
2. Life cycle inventory analysis (LCI). You compile every relevant input and output — energy, raw materials, water, emissions, waste — for each process inside the boundary. This is the data-collection heavy lifting and usually the longest phase.
3. Life cycle impact assessment (LCIA). You translate those raw flows into environmental impacts, so kilograms of assorted gases become, say, kilograms of CO2-equivalent for climate change, using an established characterisation method.
4. Interpretation. You draw conclusions, test how sensitive they are to your assumptions, and check the results are consistent with the original goal.

Crucially, these phases are iterative. What you learn during inventory or interpretation often sends you back to refine the scope. The detailed rules for how each phase must be carried out — including data quality, allocation and reporting — live in the companion standard, ISO 14044:2006.

Which standards govern life cycle assessment?

LCA is a well-standardised field. The two foundational documents are ISO 14040 (principles and framework) and ISO 14044 (requirements and guidelines); ISO 14044 has been amended twice, so a current consolidated version reads as ISO 14044:2006+A1:2017+A2:2020. Around them sits a family of related standards:

Standard	What it covers
ISO 14040:2006	Principles and framework — defines the four LCA phases
ISO 14044:2006	Detailed requirements for conducting and reporting an LCA
ISO 14067:2018	Carbon footprint of products — an LCA restricted to climate change
ISO 14071:2024	Critical review processes and reviewer competencies
ISO 14072:2024	Organisational LCA — a whole organisation, not a single product
GHG Protocol Product Standard	Product-level greenhouse-gas accounting, built on the ISO standards

A few points are worth drawing out. ISO 14067 is, in effect, an LCA narrowed to a single impact category — it quantifies a product's carbon footprint "in a manner consistent with" ISO 14040 and 14044. ISO 14071 and ISO 14072 were both upgraded from technical specifications to full international standards in 2024: 14071 sets out how an independent critical review should be run (a panel review is required by ISO 14044 for public comparative claims), and 14072 applies LCA thinking to an entire organisation. The GHG Protocol Product Standard explicitly builds on ISO 14040, 14044 and the older British specification PAS 2050, which pioneered product carbon footprinting and is still listed as current, even if it is rarely the first reference for new work.

One change to watch: on 9 February 2026, GHG Protocol announced a joint working group with ISO to develop a single, harmonised product-level greenhouse-gas accounting standard. The long-running overlap between the GHG Protocol Product Standard and the ISO 14067 carbon-footprint standard is being resolved by developing them together rather than in competition — so the two most-cited product-footprint frameworks are converging.

Where does an LCA start and stop?

The most consequential decision in any study is the system boundary — where the assessment begins and ends. The common boundaries are:

• Cradle-to-gate — raw material extraction up to the point the product leaves your factory gate, excluding distribution, use and end of life.
• Cradle-to-grave — the full life cycle, from raw materials through to final disposal or recycling.
• Gate-to-gate — only the processes inside your own operations.
• Cradle-to-cradle — a variant of cradle-to-grave where end-of-life material is designed to feed back into new products rather than be disposed of.

The boundary is not a free choice. Under the GHG Protocol Product Standard, the boundary for a final product "shall include the complete life cycle, from cradle-to-grave", whereas a cradle-to-gate boundary is a partial inventory reserved for intermediate products — and where you use it, you must disclose and justify that choice. Because this decision drives cost, effort and what claims you can defend, we cover it in depth in our guide to cradle-to-gate vs cradle-to-grave LCA boundaries.

LCA, carbon footprint or EPD — what's the difference?

Three terms get used interchangeably and shouldn't be.

A product carbon footprint (PCF) measures one impact only — greenhouse gases, in kg CO2e — under ISO 14067 or the GHG Protocol Product Standard. Every PCF is built on LCA methodology, but it answers a narrower question. It is faster and cheaper than a full LCA, but it cannot, on its own, support a broad "environmentally friendly" claim. We unpack this fully in product carbon footprint vs LCA.

An EPD (Environmental Product Declaration) is not a different type of study but a different type of output. It is a standardised, independently verified public summary of LCA results, produced under ISO 14025:2006 using product category rules. For construction products the governing rules are EN 15804+A2, and UK manufacturers usually publish through BRE Global's EPD programme or a pan-European operator such as the International EPD System. So the LCA is the analysis; the EPD is the verified, comparable report built from it.

What data does an LCA need?

An LCA is only as credible as its data, and data comes in two kinds:

• Primary data are measured directly from the processes you control — metered energy, production volumes, bills of materials, waste, transport distances, supplier-specific figures.
• Secondary data come from life cycle inventory (LCI) databases, literature or industry averages, and cover the upstream processes you cannot measure yourself.

The GHG Protocol Product Standard expects companies to collect primary data for every process under their ownership or control, and to assess all data for technological, temporal and geographical representativeness. For everything else, the field leans on shared background databases. The most widely used is ecoinvent, whose version 3.12 was released in November 2025 with more than 26,000 datasets; Sphera's Managed LCA Content and sector databases such as Agri-footprint are also common. Because databases are updated frequently and impact methods change with them, the vintage of the data behind an LCA matters — a study built on current datasets is more defensible than one leaning on figures several years old.

In practice, collecting primary data is the single longest part of most projects, which is why supply-chain data readiness does more to determine your timeline than almost anything else.

When does your business need an LCA?

For most UK businesses, an LCA is not a legal obligation — it is a commercial one. The usual triggers are:

• A customer or supply-chain request. Large buyers increasingly ask suppliers for product-level carbon or environmental data as a condition of staying on the panel.
• A construction EPD. There is no UK law mandating EPDs, but demand is driven by BREEAM credits, client specifications and public procurement. If your buyers want an EPD, you need the underlying LCA first.
• Tenders and procurement. Environmental data is now a routine scored criterion in bids, particularly in the built environment and the public sector.
• Eco-design. An LCA shows where a product's impact actually sits, so you redesign the stages that matter rather than the ones that merely feel wasteful.
• Substantiating a green claim. This is the fast-changing one.

On that last point, the rules have tightened sharply. The CMA's Green Claims Code requires environmental claims to be accurate, to consider the full life cycle, and to be backed by robust evidence — a "low carbon" claim that quietly excludes significant stages "is liable to mislead consumers". And since 6 April 2025, under the DMCC Act direct-enforcement regime, the CMA can decide for itself that a business has broken consumer law and fine it up to 10% of global turnover — without going to court. In that environment, an ISO-conformant LCA or carbon footprint is the difference between a claim you can defend and one that carries material financial risk.

For buildings specifically, the strongest existing driver is planning, not building regulations. London Plan Policy SI 2 already requires whole life-cycle carbon assessments for schemes referable to the Mayor. Nationally, though, embodied carbon remains largely voluntary: Part Z is an industry-proposed amendment that has not been enacted, and in March 2026 the government declined to mandate whole-life carbon assessments for buildings, opting for a voluntary approach (a decision publicly criticised by CIBSE). NISTA's new Whole Life Carbon Management guidance, published in March 2026, is exactly that — best-practice guidance for public programmes, not regulation. The direction of travel is clearly towards more measurement; the current reality is that market pressure is ahead of the law.

How much does an LCA cost, and how long does it take?

Pricing is not standardised, so treat any figure as indicative rather than a quote. As a rough guide to the ranges we see in the UK market, a screening or simplified single-product study typically starts around a few thousand pounds, a full ISO 14044-compliant single-product LCA commonly falls in the low tens of thousands, and complex or multi-product studies run higher still. The main cost drivers are product complexity, supply-chain data readiness, the system boundary you choose, how many impact categories you assess, and whether independent verification or a critical review is required. We break the numbers and the levers down in how much an LCA costs in the UK.

On timing, a simple cradle-to-gate screening can be done in a few weeks, while a full consultant-led LCA typically takes around three to six months — with primary data collection, again, consuming most of that time. Studies that need panel critical review or EPD verification sit at the longer end.

Getting an LCA done well

An LCA is only as useful as the decision it informs. A study built on current data, an honest boundary and a clearly defined functional unit gives you defensible claims, stronger bids and better design decisions. One built on stale figures or a conveniently narrow boundary does the opposite — and, under the current green-claims regime, can expose you rather than protect you.

Carbon Managers has been building GHG Protocol-aligned footprints and life cycle assessments for UK businesses since 2007. We produce the ISO 14040/14044-conformant study that underpins a product carbon footprint, a customer data request or the LCA behind a construction EPD — while independent verification and registration stay, correctly, with an accredited operator. If you have been asked for product-level environmental data, or you want a claim you can stand behind, our life cycle assessment service is the place to start.