Scope Emissions Calculation Guide

Overview of Scope Emissions

The Greenhouse Gas (GHG) Protocol Corporate Accounting and Reporting Standard categorises emissions into three scopes to provide a framework for comprehensive carbon accounting. UK SRS S2 requires reporting of Scope 1 and 2 emissions, with Scope 3 required where material. For comprehensive UKSRS guidance on emissions reporting requirements, see uksrs.org.uk.

The existing GHG Protocol standards remain in force. A revision programme is running across four technical working groups — Corporate Standard, Scope 2 Guidance, Scope 3 Standard and a new Actions & Market Instruments workstream — but as of 27 July 2026 the mid-2026 public consultation drafts for the Corporate Standard and the Scope 3 Standard had not launched: they are expected, not yet open.

Scope 2 is further ahead. Its first public consultation ran from 20 October 2025 to 31 January 2026, covering revised location-based and market-based methods, and a second consultation is to follow. Until GHG Protocol communicates otherwise, current standards and guidance stay in effect and any transition period is undecided — so calculate against the standards as they stand today.

Scope 1: Direct Emissions

Direct greenhouse gas emissions from sources owned or controlled by your organisation.

Sources of Scope 1 Emissions

Stationary combustion: Fuel burning in boilers, furnaces, turbines
Mobile combustion: Company-owned or controlled vehicles, aircraft, ships
Fugitive emissions: Refrigerant leaks, natural gas leaks
Process emissions: Chemical reactions, industrial processes

Calculation Methodology

Emissions = Activity Data × Emission Factor × Global Warming Potential

Example: Natural Gas Consumption

Activity Data: 100,000 kWh natural gas consumed
Emission Factor: 0.18316 kg CO₂/kWh — illustrative, taken from the DESNZ 2024 set. Use the current 2026 factors, published by DESNZ on 11 June 2026, for a live calculation
Calculation: 100,000 × 0.18316 = 18,316 kg CO₂
Result: 18.3 tonnes CO₂

Scope 2: Indirect Energy Emissions

Indirect emissions from purchased electricity, heat, steam, and cooling consumed by your organisation.

Scope 2 Categories

Location-based: Uses average emission factors for electricity grids
Market-based: Uses emission factors from specific electricity suppliers

UK Electricity Calculation

Location-Based Method

Activity Data: 50,000 kWh electricity purchased
Grid Factor: 0.193 kg CO₂/kWh — illustrative, UK grid, DESNZ 2024 set. Take the live figure from the 2026 conversion factors published on 11 June 2026
Calculation: 50,000 × 0.193 = 9,650 kg CO₂
Result: 9.7 tonnes CO₂

Market-Based Method

Renewable electricity: 0 kg CO₂/kWh (with valid certificates)
Supplier-specific factor: Use supplier's generation mix
Residual mix factor: For uncertified electricity

Scope 3: Other Indirect Emissions

All other indirect emissions in your value chain, including upstream and downstream activities.

Scope 3 Categories

Upstream Activities

Category 1: Purchased goods and services
Category 2: Capital goods
Category 3: Fuel- and energy-related activities
Category 4: Upstream transportation and distribution
Category 5: Waste generated in operations
Category 6: Business travel
Category 7: Employee commuting
Category 8: Upstream leased assets

Downstream Activities

Category 9: Downstream transportation and distribution
Category 10: Processing of sold products
Category 11: Use of sold products
Category 12: End-of-life treatment of sold products
Category 13: Downstream leased assets
Category 14: Franchises
Category 15: Investments

Common Scope 3 Calculations

Business Travel (Category 6)

Activity Data: 10,000 km business travel by car
Emission Factor: 0.16 kg CO₂/km (average UK car)
Calculation: 10,000 × 0.16 = 1,600 kg CO₂
Result: 1.6 tonnes CO₂

Purchased Goods (Category 1)

Spend-based: £ spend × emission factor per £
Activity-based: Physical quantity × emission factor
Supplier-specific: Data from suppliers

UK-Specific Guidance

DESNZ Emission Factors

Use the UK government conversion factors published annually each June by the Department for Energy Security and Net Zero (DESNZ). The current set is Greenhouse gas reporting: conversion factors 2026, published on 11 June 2026, with an accompanying methodology paper and major-changes report.

Two things worth getting right. The factors are DESNZ publications, not BEIS or Defra ones, whatever an older source may say. And DESNZ conversion factors are not the same thing as Defra's spend-based emissions multipliers published with the UK and England carbon footprint statistics.

Illustrative UK factors (2024 set — superseded)

The figures below are retained only to show the shape of the calculation. Take live values from the current 2026 publication.

Grid electricity: 0.193 kg CO₂e/kWh
Natural gas: 0.18316 kg CO₂e/kWh
Petrol: 2.196 kg CO₂e/litre
Diesel: 2.512 kg CO₂e/litre

UK SRS Requirements

Scope 1 & 2: Mandatory for all in-scope companies per UK SRS S2
Scope 3: Required across all 15 categories where material under UK SRS S2, measured per the GHG Protocol Scope 3 Standard. Neither the standard nor UK SRS sets a numeric materiality percentage
Biogenic carbon: Report separately
Location and market-based: Report both Scope 2 methods per the GHG Protocol Scope 2 Guidance

Calculation Best Practices

Data Collection

Primary data preferred: Direct measurement where possible
Consistent boundaries: Align with financial reporting
Regular updates: Use current emission factors annually
Documentation: Maintain calculation methodologies and assumptions

Quality Assurance

Data validation: Check for errors and outliers
Uncertainty assessment: Understand data limitations
Third-party review: Independent verification where required
Continuous improvement: Enhance data quality over time

Common Challenges

Data Availability

Scope 3 data gaps: Limited supplier information
Estimation methods: Use proxy data and industry averages
Data collection systems: Implement robust tracking processes

Materiality Assessment

Screening approach: Initial assessment using estimates
Quantitative screening: Rank categories by estimated contribution — no fixed percentage threshold is set by the GHG Protocol or by UK SRS
Qualitative factors: Consider stakeholder expectations

Getting Started

Begin your emissions calculation by establishing organisational boundaries and identifying your most significant emission sources across all three scopes.

Then check two things before you publish: that the conversion factors you used are the current DESNZ 2026 set, and that you have calculated against the GHG Protocol standards as they stand today rather than against a draft revision that has not yet opened for consultation.

UK SRS Compliance Guide Implementation Timeline