Carbon Footprint Scenario Calculator

Check your inventory boundary

LPG, other fuels, refrigerants, process emissions, purchased steam, heat and cooling, and Scope 3 are outside this tool. The GHG Protocol Scope 2 Guidance covers purchased energy and distinguishes accounting methods; the electricity factor here is one location-based input, not a market-based calculation.

What the calculation does

The tool has four fixed lines: electricity in kWh, natural gas in m³, diesel in litres and petrol in litres. For each line it multiplies your quantity by your factor in kgCO2e per unit and divides by 1,000 to give tonnes of CO2e. The three fuel lines are added and labelled fuel combustion, the electricity line is labelled electricity, and the total is the sum of both. If you enter a headcount above zero, the total is divided by it. A result appears only when every quantity is filled in, no value is negative, every nonzero quantity has a factor, and the headcount is a whole number.

Nothing is looked up. The tool holds no factor table, applies no default year, does not convert between units, and does not know whether a factor is location-based, market-based, combustion-only or lifecycle. Those properties belong to the factor you type in.

Worked example

The factors below are round placeholders chosen to keep the arithmetic readable. They are not published emission factors and should not be reused. Suppose a site used 120,000 kWh of electricity, 18,000 m³ of natural gas and 9,000 litres of diesel, no petrol, with 40 employees, and the entered factors are 0.25, 2 and 2.5 kgCO2e per unit.

• Electricity: 120,000 × 0.25 ÷ 1,000 = 30 tCO2e
• Natural gas: 18,000 × 2 ÷ 1,000 = 36 tCO2e
• Diesel: 9,000 × 2.5 ÷ 1,000 = 22.5 tCO2e
• Fuel combustion entered: 36 + 22.5 + 0 = 58.5 tCO2e; subtotal: 58.5 + 30 = 88.5 tCO2e
• Per employee: 88.5 ÷ 40 = 2.2125, shown as 2.21 tCO2e

Running the calculator's function on these entries returns the same values. Changing only the electricity factor to 0.20 gives 24 tCO2e for electricity and 82.5 tCO2e in total, so a 20% change in one factor moved the total by about 7%.

Why the result can mislead

The result is only as complete as its four lines. A site that also uses LPG, runs refrigeration equipment or buys steam will see a subtotal that looks precise and leaves those out. Quantity and factor must share a unit: a gas factor given per kWh applied to a volume in m³ gives a wrong answer without any warning. There is one electricity line and one factor, so a business with sites on different grids should run one scenario per grid and add the totals by hand.

The per-employee figure moves with the denominator: the same 88.5 tonnes is 1.77 per head at 50 employees. It also mixes office staff with workers at energy-intensive sites, so it is useful only for tracking your own boundary over time. Finally, comparing this year's subtotal with last year's means little if the factors came from different years or methods.

Where factors and methods are published

• The GHG Protocol Scope 2 Guidance describes accounting for purchased electricity, steam, heat and cooling, and its page refers to quality criteria for contractual instruments used in the market-based method.
• The UK government publishes annual conversion factors for company reporting for activity data such as fuel volume and electricity use. The collection says it is designed for UK organisations and for international companies reporting UK operations, and that users should document their chosen method.
• The US EPA's GHG Emission Factors Hub offers default factors for organisational reporting, including stationary and mobile combustion and electricity by grid region. When we opened it the page described the 2025 version.

The three pages were opened on 3 October 2026. They are sources of methods and factors; they are not endorsements of this calculator, and you should choose the factor set that matches your geography, year and accounting method.