Carbon Calculator Guide

Get all the data you’ve been collecting ready to enter into the calculators. Remember, this is your first try at measuring your carbon footprint, so just go for it! Make the data as accurate as you can for now, but don’t get bogged down with making it ‘perfect’. You can always refine the data each time you measure your carbon footprint and get more experienced.

We suggest you measure your Scope 1 and Scope 2 emissions. For Scope 3 it’s: employee commuting, business travel including accommodation, employees working from home, water usage, waste and purchased goods and services (measured by monetary value) as a minimum. Scope 3 emissions beyond our suggested minimum can be extremely difficult to measure and we don’t cover that in this course, but you can use our list of useful organisations to find help with calculating these emissions.

Main record

A key element of measuring your carbon footprint is keeping your data organised. It’s important that you keep a main record of your carbon footprint emissions. This should include a span of data from the very high level all the way down to the nitty gritty. Your main record should include your total overall emissions for the year, the total of each Scope and the total of each separate aspect that you measure.

You can then use it to compare yearly emissions and see how and where they’ve changed – hopefully decreasing! You can use our yearly emissions template to keep a main record of all your emissions, which lists our minimum requirements.

Calculating your company’s carbon footprint

We’re signposting you to two carbon calculators. This is because there isn’t currently a carbon calculator available that includes every aspect you need to measure, so we’ve created our own for the aspects not included in calculator one. Using these calculators, you’ll measure all our minimum requirements. If you want to measure over and above our minimum requirements, you can use our list of useful organisations to find help with calculating these emissions.

Calculator one is on Climate Impact Partners website and calculator two is our Heart of the City carbon calculator. We’ll talk through what each calculator measures further in this resource.

Once you’ve used the calculators to measure an aspect of your carbon footprint, make sure you enter the data into your main record.

Calculator one

Use Climate Impact Partners carbon calculator  to measure these emissions:

Scope 1

• Gas – grid connection
• Transport – Company owned vehicles fuel
• Fuel in other company controlled assets – generators and machinery

Scope 2

• Electricity – Purchased electricity: location based (every organisation use)
• Electricity – Purchased electricity: market based (use in additional to location based if your organisation purchases renewable electricity)

Scope 3

• Transport – Employee commuting
• Transport – Business travel
• Accommodation – Business travel accommodation
• Waste

How to use

Scroll down to the ‘calculate now’ subheading.

Click on the dropdown menu and choose the category relevant to the aspect you’re measuring. The categories that are relevant to what you’re measuring are in bold:

Scope 1 

• Gas: 4) Energy – use energy type: natural gas
• Transport – company owned vehicles: 3) Road transport
• Fuel in other company controlled assets – generators and machinery: 4) Energy

Scope 2 

• Electricity – Purchased electricity: location based – 4) Energy (enter total consumption)
• Electricity – Purchased electricity: market based – 4) Energy (enter total non-renewable consumption)

Scope 3

• Transport – employee commuting: 3) Road transport
• Transport – business travel: 2) Flights and 3) Road transport
• Accommodation – business travel accommodation: 6) Accommodations
• Waste: 9) Waste

Enter the data you’ve collected for each aspect. Look at our carbon footprint guide to understand what data you need and where you can find it.

The carbon emissions for the data you’ve entered will show in the ‘carbon emissions’ box in tonnes of CO2e. Be aware that this number will be overwritten once you enter new data.

If you’re entering one piece of data for an aspect, once it’s calculated enter the total carbon emissions into your main record document.

If you’re entering data multiple times for an aspect, keep a note of each subtotal and add them together at the end for the aspect’s total emissions. Then enter the total carbon emissions into your main record document. For example, you’ll have multiple data entries for employee commuting if some people commute by tube and others by bus.

Calculator two

Use our Heart of the City carbon calculator to measure these emissions:

Scope 3

• Water
• Employees working from home
  • a) Basic working from home method

OR

• • b) Advanced working from home method

OR

• • c) Hourly working from home method
• Purchased goods and services (measured by monetary value)

How to use

Work through each tab: 1 (water), 2a or 2b or 2c (working from home) and 3 (purchased goods and services).

Enter the data you’ve collected for each aspect. Look at our carbon footprint guide to understand what data you need and where you can find it.

Enter your data into the blue cells and the total for each aspect will show in the orange cell.

Enter the total from the orange cell into your main record document.

Our calculator will be updated yearly, so make sure you download the most up to date version when you’re using this calculator.

Other

Scope 1

• Refrigerants

If you’ve collected data to measure refrigerants, use this equation to calculate the emissions:

Amount of gas used to top up appliance in kg X gas global warming potential = Refrigerants kgCO2e

Then enter the total carbon emissions into your main record document.

This was last updated in March 2024 by Heart of the City. We’ve created these resources for individual SMEs to use. None of our content is to be adapted, reused or repurposed for commercial use.

Climate for SMEs: 4 Steps to Action is funded by the City of London Corporation in support of its Climate Action Strategy targets for a net zero and resilient Square Mile.