Upload a bill

Guide

How to calculate your organization's carbon footprint

The practical walkthrough: set a boundary, understand Scope 1, 2 and 3, work out which document proves which number, then find the right calculator for every category — for a company, nonprofit, school, or public agency.

Last updated July 2026

Start with a boundary, not a spreadsheet

Before any number gets calculated, decide what "your organization" means for this exercise. That's the organizational boundary — which entities, sites, and activities count. The GHG Protocol offers two approaches:

  • Operational control — count everything you operate day to day, even if you don't legally own it (a leased office, a rented delivery van).
  • Equity share — count a proportional share of everything you hold financial interest in, matching your ownership percentage.

Most companies, nonprofits, schools, and public agencies use operational control, because it's simpler to apply and matches how most people already think about "our building, our fleet, our staff." Pick one, write it down in a sentence, and apply it consistently — a footprint that quietly switches boundary definitions between years isn't comparable to itself.

Once the boundary is set, the next decision is scope, which is where the real work of counting begins.

Scope 1, 2 and 3, in plain words

The GHG Protocol's three scopes answer one question three times: whose fuel got burned, and where?

  • Scope 1 — you burned it. Diesel in a vehicle you own or lease, gas under a kitchen hob, petrol in a site vehicle, and refrigerant gas that leaked from an air-conditioner or cold room. These are direct emissions from sources under your control.
  • Scope 2 — the power station burned it for you. Every kWh on your electricity bill was generated somewhere, using a fuel mix specific to your grid, and a factor converts that kWh into kgCO₂e.
  • Scope 3 — someone else burned it because of you. What you purchase, how goods move to and from you, how staff travel and commute, and what happens to your waste after it leaves. Scope 3 is usually the largest of the three and the hardest to pin down, because the burning happens outside your walls.

None of this changes based on what kind of organization is doing the counting. A company's delivery van, a school's minibus, and a hospital's generator are all Scope 1 for exactly the same reason: someone in the organization controls the asset that burned the fuel.

Which document proves which number

Carbon accounting turns out to be mostly a filing exercise. Work through a year of paperwork and sort it:

| You have this document | It proves | Which scope | | --- | --- | --- | | Electricity bill | kWh used | Scope 2 | | Fuel-card statement, pump receipts | Litres of diesel/petrol/LPG | Scope 1 | | Gas bill | kWh of gas | Scope 1 | | Aircon/refrigeration service invoice showing gas top-up | kg of refrigerant, by type | Scope 1 | | Supplier invoices for goods and services | Spend or quantities purchased | Scope 3 (cat. 1/2) | | Freight/courier/forwarder invoices | Tonne-km by transport mode | Scope 3 (cat. 4/9) | | Flight itineraries, hotel folios | Passenger-km, room-nights | Scope 3 (cat. 6) | | Staff address or transport survey | Commute distance by mode | Scope 3 (cat. 7) | | Waste-disposal or recycling invoices | Tonnes by treatment route | Scope 3 (cat. 5) | | Water utility bill | m³ supplied and treated | Scope 3 (cat. 1, sometimes cat. 5) |

If a document is sitting in your accounts-payable folder, it almost certainly maps to a row in this table. That's the whole trick: a carbon footprint is an accounts-payable folder, resorted.

The category-by-category map

This is the practical part — every relevant calculator on this site, mapped to the number it produces. Run the ones that apply to your organization; a first pass rarely needs all of them.

The fast, whole-organization option. If you want one screening number across every major category before drilling into specifics, start with the organization footprint calculator — it covers electricity, gas, fuel, refrigerant, flights, hotel stays, commuting, waste, and water in a single page, region-aware throughout.

Scope 2 — electricity. Business electricity (any country) covers 13 regions with country-specific grid factors; business electricity (Singapore) uses the official EMA factor directly if that's your only site. For a household or home-office component, there's home energy.

Scope 1 — fuel and refrigerant. Fleet fuel covers diesel and petrol in owned or leased vehicles; refrigerant & air-con leaks covers six refrigerant gas types by kilograms topped up.

Scope 3 category 1/2 — purchased goods and services. Purchased goods & services (spend-based) turns eight common spend categories into an order-of-magnitude estimate when you don't have supplier-specific data; office IT equipment covers laptops, monitors, and servers specifically, both embodied and in-use.

Scope 3 category 4/9 — freight and logistics. Freight & shipping covers road, sea, air, and rail per tonne-kilometre.

Scope 3 category 5 — waste. Waste disposal covers commercial waste, food and drink waste, and paper/board, by disposal route.

Scope 3 category 6 — business travel. Business flights covers per-trip emissions by haul length; hotel operations covers room-nights, laundry, and kitchens for a hotel itself, and also supplies the per-room-night factor used when counting your own staff's hotel stays.

Scope 3 category 7 — employee commuting. Employee commuting covers a simple annual commute survey by car fuel type.

Scope 3 category 1 (and sometimes 5) — water. Water & wastewater covers mains supply and treatment per cubic metre.

Site-type calculators, when your organization fits a pattern. Some organizations find it faster to fill in one purpose-built page than to assemble several generic ones: school & campus, clinic & healthcare, manufacturing site, restaurant & F&B, retail store, warehouse & logistics, construction project, events & conferences, and the fast general-purpose office footprint estimate. Each bundles the fields most relevant to that kind of site, so you fill in one page instead of assembling several category calculators by hand.

Personal footprints. If an individual — a founder, a staff member building their own number for an employer's survey — wants a personal figure rather than an organizational one, home energy and personal flights cover the household side.

When a screening number is enough, and when you need documents

A calculator result is a screening number: fast, transparent, and good enough to understand your rough shape and rank your categories by size. It's the right tool the first time you measure something, or when you're checking whether a category is worth the effort of deeper data collection.

A document-based number is what you need when a framework, a customer questionnaire, or an auditor wants figures tied to evidence — a specific bill, a specific invoice, a specific service record — rather than a total you typed in from memory or a spreadsheet. That's what uploading your documents is for: PDFs, CSVs, or photos of bills and invoices get read, classified into the right scope and category automatically, and every extracted figure keeps a link back to the source document and a confidence score. It's the same arithmetic as the calculators, run against evidence instead of typed totals, and it's the version that survives a "where did this number come from?" question later.

A sensible sequence: run the relevant calculators first to see your rough shape and find your largest categories, then upload documents for the categories that turn out to matter, to get a defensible, evidenced number for the ones you'll actually need to show someone.

What this method doesn't cover

  • Assurance. Neither the calculators nor the document upload constitute external audit or assurance. They produce a well-sourced estimate with full factor provenance — the organization remains responsible for its own disclosures under whatever framework applies to it.
  • The rarer Scope 3 categories. Franchises, investments, downstream leased assets, and end-of-life treatment of sold products exist in the GHG Protocol's full 15-category list but rarely apply to a first footprint; skip them and note the gap in your methodology rather than guessing.
  • Product-level life-cycle assessment. This method produces an organizational footprint — total emissions for the entity as a whole — not a per-unit carbon footprint for an individual product, which is a separate and more detailed exercise.
  • Currency and unit conversion. Spend-based estimates need EUR; physical calculators need the units on the field labels. Getting the conversion right before entering a number matters as much as the factor itself.

Why the arithmetic is identical everywhere

A kilowatt-hour, a litre of diesel, a tonne of waste, and a kilogram of refrigerant carry the same emissions regardless of who bought them. That's what makes one method work across a company, a nonprofit, a school, and a public agency: the GHG Protocol's scope and category definitions describe physical activities, not organization types. The number this method produces feeds directly into ISSB IFRS S2, GRI 305, CDP questionnaires, and most national disclosure codes — none of them invent a separate accounting method, they just ask for the same three piles of numbers in a particular format. Singapore-listed organizations and their suppliers face a specific timeline on top of this universal method — see the SGX climate reporting deadlines guide — but the underlying calculation on this page is the same one every organization, anywhere, is doing.

Sources

Frequently asked questions

Where do I actually start?
With your electricity bill. It's the document almost every organization already has, it usually maps to the largest single number in a first-pass footprint, and it takes one calculation. Run it through the electricity calculator, then work outward to fuel, then to Scope 3, using the category map below.
How much of my footprint can I do with calculators versus needing to upload documents?
Calculators are the right tool when you know your annual totals — kWh, litres, tonnes — and want a fast, transparent number with the factor shown. Uploading documents is the right tool when you have a stack of bills and invoices and want the figures extracted and classified for you, especially across many months or many sites, or when you need an audit trail tying each number back to a specific document.
Do I need to measure all 15 Scope 3 categories?
Almost never for a first footprint. Most organizations get 80 to 90 percent of their Scope 3 total from four or five categories — purchased goods and services, freight, business travel, employee commuting, and waste. Start with those, using the map below, and expand only if a specific framework or questionnaire asks for a category you've skipped.
Does this method work the same for a nonprofit or school as for a company?
Yes. The GHG Protocol's scope and category definitions don't reference company structure, revenue, or sector — they reference physical activities: electricity used, fuel burned, goods purchased, waste disposed. A school's kWh and a company's kWh go through the identical calculation. Only the mix of categories that matter tends to differ — a school cares about school-transport diesel and food waste, a manufacturer cares about process refrigerant and freight.
What if I only have a rough sense of my spend, not physical quantities?
Use a spend-based estimate as your starting point, then refine categories that turn out to be large with real activity data. The purchased goods & services calculator does exactly this for eight common spend categories, denominated in EUR, and is explicit that the result is an order-of-magnitude screening number rather than a disclosure-grade figure.