A carbon footprint is calculated by multiplying each activity (such as kWh of electricity or litres of fuel) by an emission factor — the average kilograms of CO2e released per unit — and summing the results. This calculator uses electricity 0.35 kgCO2e/kWh, natural gas 0.20 kgCO2e/kWh, petrol 2.31 kgCO2e/litre and diesel 2.68 kgCO2e/litre, then divides the total kilograms by 1,000 to give tonnes of CO2e (tCO2e).

Scope 1 covers direct emissions from sources you own or control — for example burning natural gas in a boiler or petrol and diesel in company vehicles. Scope 2 covers indirect emissions from the generation of the electricity, heat or steam you purchase from the grid. Scope 3 covers all other indirect emissions across your value chain, such as purchased goods, business travel and use of sold products.

It is indicative only. The tool uses standard EU-average emission factors that do not reflect your specific country, year, energy supplier or grid mix, and it only covers Scope 1 and Scope 2. Treat the result as a rough estimate, not a reportable figure. CarbonTool uses precise, source-specific emission factors, tracks data quality for every entry and builds a full GHG-Protocol inventory that stands up to audit.

Scope 3 covers indirect value-chain emissions — purchased goods and services, transport, business travel, waste and the use of sold products — and is usually the largest part of a footprint. It requires supplier data collection and spend- or activity-based methods rather than a few energy inputs. CarbonTool includes a supplier portal and PCAF-style scoring to collect and quantify it; see the supply chain platform.

This free tool focuses on Scope 1 and Scope 2 because those can be estimated from a handful of energy and fuel inputs. Scope 3 typically accounts for 70–90% of total emissions but needs value-chain and supplier data to quantify. To capture your full footprint across all three scopes, build a complete inventory in CarbonTool.