Measure Your
Carbon Impact
A GHG Protocol-aligned carbon footprint calculator covering all three scopes. Emission factors verified against DEFRA 2023 UK Government guidance. Results give you a full scope breakdown — the starting point for a reduction plan.
Company Details
Tell us about your organisation so we can contextualise your footprint.
On-Site Fuel &
Refrigerant Use
Emissions from sources your organisation directly owns or controls. Leave blank for activities that don’t apply.
Grid Electricity
GHG Protocol requires both location-based and market-based Scope 2 reporting where possible. Select your approach below.
Business Travel &
Employee Commuting
Enter annual organisation-wide totals. For passenger-km, multiply passengers × distance in km. Aviation factors include radiative forcing.
Procurement, Logistics
& Waste
Indirect emissions from goods, services, logistics, and waste generated by your organisation.
Office Operations &
Digital Footprint
Day-to-day office activities, digital infrastructure, and employee remote working.
Proxy Estimator
If your activity data is incomplete, proxy estimates based on headcount and office size can fill the gaps. Tick each category where you’ve already entered direct data — the proxy reduces automatically with no double-counting.
Your Carbon
Footprint Baseline
Calculator v4 · March 2026 · Review factors each July when DEFRA publishes updates · This tool provides indicative estimates only; formal GHG inventories require third-party verification.
Methodology Statement
Full methodological basis for this calculator. Version 4 · March 2026.
This calculator follows the GHG Protocol Corporate Accounting and Reporting Standard (World Resources Institute / WBCSD, 2004; revised 2013), the globally recognised framework for corporate greenhouse gas inventories. Emissions are quantified and reported across three scopes as defined by the GHG Protocol.
Organisational boundary is assumed on an operational control basis: all facilities and operations over which the reporting organisation has operational control are included.
All emission factors are sourced from DEFRA UK Government GHG Conversion Factors for Company Reporting 2023, published July 2023. These are the most recently available factors at the time of this calculator's publication. Factors should be reviewed and updated each July when DEFRA publishes new annual guidance.
All factors express emissions in kg CO²e (carbon dioxide equivalent), incorporating CO², CH&sub4;, and N&sub2;O using IPCC Fifth Assessment Report (AR5) Global Warming Potentials unless otherwise stated. The refrigerant factor (R-410A) uses IPCC AR4 GWP as published in DEFRA 2023.
Flight factors include Radiative Forcing (RF) uplift, reflecting the additional climate impact of aviation at altitude. This is consistent with DEFRA guidance and GHG Protocol best practice for air travel.
| Scope | Definition | Categories Covered |
|---|---|---|
| Scope 1 | Direct emissions from owned/controlled sources | Stationary combustion (gas, diesel, petrol, LPG, heating oil); fugitive refrigerant emissions |
| Scope 2 | Indirect emissions from purchased electricity | Grid electricity — location-based (DEFRA UK grid average) or market-based (adjusted for renewable energy contracts) |
| Scope 3 | All other indirect value chain emissions | Categories 1, 3, 4, 5, 6, 7, 13 (partial) — see table below |
| GHG Protocol Category | Name | Coverage |
|---|---|---|
| Cat 1 | Purchased goods and services | Spend-based: physical goods (0.23 kg/£) and purchased services (0.12 kg/£) as separate fields; capital IT equipment (0.40 kg/£) |
| Cat 3 | Fuel and energy-related activities | Well-to-tank upstream emissions for gas, diesel, petrol, LPG, heating oil (optional toggle) |
| Cat 4 | Upstream transportation | Freight by van, HGV, sea, and air (t-km); courier parcels |
| Cat 5 | Waste generated in operations | Landfill (0.58742 kg/kg, DEFRA 2023) and recycling (0.021 kg/kg) |
| Cat 6 | Business travel | Flights by class and route type (economy/premium/business/first, incl. RF); rail, bus, taxi; car business mileage (petrol/diesel and EV); hotel UK and international; training travel |
| Cat 7 | Employee commuting | Car (petrol/diesel), EV, National Rail, bus, underground/metro |
| Cat 13 | Downstream leased assets | Water supply and wastewater (facility operations proxy) |
The GHG Protocol Scope 2 Guidance (2015) requires dual reporting where possible: a location-based figure (using grid average factors) and a market-based figure (using supplier-specific or contractual factors).
Location-based: UK grid average factor of 0.20705 kg CO²e/kWh (DEFRA 2023) applied to all grid electricity consumed.
Market-based: Where a renewable energy contract, Power Purchase Agreement (PPA), or Renewable Energy Guarantee of Origin (REGO) certificate covers a portion of electricity consumption, the market-based Scope 2 figure is reduced proportionally. Electricity covered by a qualifying instrument is treated as zero-carbon for Scope 2 purposes; the remainder uses the grid average factor. Users should retain documentation of their renewable energy instrument for audit purposes.
Upstream (well-to-tank) emission factors capture the greenhouse gas emissions from extracting, refining, and transporting fuels before combustion. These are reported under GHG Protocol Category 3 (fuel and energy-related activities).
WTT factors used (DEFRA 2023): Natural Gas 0.02956 kg CO²e/kWh; Diesel 0.61024 kg CO²e/litre; Petrol 0.53349 kg CO²e/litre; LPG 0.17536 kg CO²e/litre; Heating Oil 0.59295 kg CO²e/litre.
WTT is included as an optional toggle. It is excluded by default for comparability with inventories that report combustion-only Scope 1. Where WTT is enabled, this should be disclosed in the inventory report.
Aviation emission factors vary significantly by seat class, reflecting the greater space and structural weight attributed to premium cabins. DEFRA 2023 factors (including RF) used:
| Route Type | Class | Factor (kg CO²e/pass-km) | vs Economy |
|---|---|---|---|
| Short-haul (<3,700 km) | Economy | 0.15845 | 1.0× |
| Short-haul | Business | 0.27967 | 1.76× |
| Long-haul (>3,700 km) | Economy | 0.13028 | 1.0× |
| Long-haul | Premium Economy | 0.15894 | 1.22× |
| Long-haul | Business | 0.28808 | 2.21× |
| Long-haul | First | 0.39637 | 3.04× |
Where direct activity data is unavailable, proxy estimates based on employee headcount and office floor area can supplement the inventory. Category weights sum to exactly 100%; ticking all categories reduces the proxy contribution to zero, preventing double-counting.
Category weights reflect approximate proportions of a typical UK office-based organisation's emissions profile. Proxy-based results are clearly separated from direct activity data in the results output and should be labelled as estimates in any disclosure document.
- Single UK grid factor: A single national average electricity factor is used. Organisations with site-specific grid connections should use supplier-specific factors in formal disclosures.
- Commuting data: Commuting emissions depend on self-reported or estimated employee travel patterns. A ±30% uncertainty range is typical for this category.
- Food factor: The default 5.0 kg CO²e/meal assumes a mixed diet including meat. This figure is 60–85% lower for vegetarian or vegan meals.
- Purchased goods (spend-based): Spend-based factors carry high uncertainty (typically ±50%) and are a last-resort approach. Activity-based data should be used in formal disclosures wherever available.
- IT and digital factors: Cloud, mobile, and device-hour factors carry high uncertainty and are appropriate for indicative assessments only.
- Categories not covered: Downstream transport (Cat 9), processing of sold products (Cat 10), use of sold products (Cat 11), end-of-life of sold products (Cat 12), franchises (Cat 14), investments (Cat 15).
- Biogenic CO²: Not separately reported. Biogenic emissions from biomass fuels should be reported separately in formal disclosures.
Angel Offsets is a carbon reduction consultancy. We do not sell, broker or recommend carbon credits, and this calculator does not price or quantify offsets. The output is a measured baseline, nothing more.
That baseline is the input to a reduction programme: we rank emission sources by size and by how practically they can be cut, model the effect of specific interventions, and set a reduction trajectory with dated milestones. The result is documented as a Carbon Reduction Plan suitable for PPN 06/21-style submissions, supplier questionnaires and annual reporting.
Because we have no commercial interest in credit sales, the measures we recommend are selected purely on impact, cost and evidence — which is what makes the resulting claims defensible.
Calculator version: v4. Emission factors last updated: July 2023 (DEFRA 2023). Methodology statement issued: March 2026.
DEFRA publishes updated conversion factors annually, typically in July. This calculator and its methodology statement should be reviewed and updated each year.
Issued by Angel Offsets. This tool is provided for indicative purposes and does not constitute a formal GHG inventory or verified emissions report. For a verified corporate carbon footprint, organisations should engage an accredited third-party verification body.