Office carbon footprint calculator (fast whole-office estimate)

How this calculation works

This page is built for one job: getting a serviceable whole-office emissions number out of the three bills almost every office already has, before you commit to a full carbon inventory. It is three multiplications and one addition:

Emissions (kgCO₂e) = electricity (kWh) × grid factor + gas (kWh) × gas factor + diesel (litres) × diesel factor

Each field maps to a different part of the GHG Protocol. Purchased electricity is Scope 2 — indirect emissions from power generated somewhere else on your behalf. Gas burned in the pantry or a heating system, and diesel burned in a backup generator or a company vehicle, are Scope 1 — fuel combusted in equipment you own or control.

For a typical services office — desks, air-conditioning, a server cupboard, perhaps a van — these three lines are most of what a Scope 1 and 2 report will ask of you. That is the deliberate trade this calculator makes: the 80% answer in five minutes, honest about the missing 20%, with pointers to the dedicated calculators when a line item deserves more care.

The factors behind each field

Pick your country and the electricity field uses that grid's emission factor. Gas and diesel use the UK Government's 2025 conversion factors (DEFRA/DESNZ), the standard international default where no national factor is published.

| Input | Factor | Source and licence | | --- | --- | --- | | Electricity (Singapore) | 0.4020 kgCO₂e/kWh (2024 data year, current) | EMA, Singapore Energy Statistics 2025 — Singapore Open Data Licence | | Natural gas | 0.18293 kgCO₂e/kWh | UK DEFRA/DESNZ 2025 — Open Government Licence v3.0 | | Diesel | 2.686 kgCO₂e/litre | UK DEFRA/DESNZ 2025 — Open Government Licence v3.0 |

Singapore's grid factor moves year to year: 0.4020 kgCO₂e/kWh is what the calculator currently applies, for the 2024 data year (Singapore Energy Statistics 2025 release); 0.4085 kgCO₂e/kWh remains correct for activity dated within 2024, as the 2023 data year figure. The calculator applies the year that matches your activity dates and prints it under the result.

For the other regions in the dropdown: the UK uses 0.207 kgCO₂e/kWh (DEFRA 2025) and the US uses 0.3712 (EPA eGRID 2022, public domain). The remaining countries use approximate factors derived from Ember's yearly electricity data (published CC-BY): Malaysia ~0.61, Indonesia ~0.69, Thailand ~0.45, Vietnam ~0.48, the Philippines ~0.61, Japan ~0.46, China ~0.58, India ~0.71, Australia ~0.53, and a world average of ~0.48 kgCO₂e/kWh. The tilde matters — those Ember-derived values are good enough for a first estimate, but worth replacing with an official national factor before anything goes into a formal disclosure.

A worked example

A 25-person office pulls together one month of paperwork:

• 2,000 kWh of electricity from the SP Group bill
• 150 kWh of pantry gas from the gas bill
• 40 litres of diesel — the monthly generator test plus a delivery van

2,000 kWh × 0.4020 = 804.0 kgCO₂e 150 kWh × 0.18293 = 27.4 kgCO₂e 40 litres × 2.686 = 107.4 kgCO₂e Total ≈ 939 kgCO₂e ≈ 0.94 tCO₂e for the month

Run twelve similar months and the office lands near 11.3 tCO₂e a year across Scope 1 and 2. Just as useful as the total is the split: electricity is about 86% of this example, which tells you exactly where a reduction effort — or a more careful calculation — should start. For that deeper pass, the business electricity calculator handles the electricity line on its own, and the fleet fuel calculator does the same for vehicles if your diesel spend is more than a generator test.

What this calculator doesn't cover

A fast estimate earns trust by being clear about its edges:

• Scope 3 entirely. Business travel, employee commuting, purchased goods and services, freight, waste and water are all out of scope here. For many offices these exceed Scope 1 and 2 combined — they are simply a different, slower measurement job.
• Refrigerants. Top-ups to air-conditioning systems are Scope 1 and can be material for buildings with large chiller plants. This tool has no refrigerant field; a full inventory needs your aircon servicing records.
• Purchased cooling or heat. If your building bills you for district cooling or chilled water, that is Scope 2 as well, but it is not covered by the electricity field — don't fold it into your kWh.
• Market-based accounting. If you buy renewable energy certificates or a green tariff, the GHG Protocol lets you show a market-based Scope 2 figure alongside this location-based one. This tool computes the location-based number only.
• Rent-inclusive utilities. If electricity is bundled into your rent, you need the kWh your landlord attributes to you. A dollars-only estimate is weaker evidence than a metered figure — ask for the meter data.
• Approximate grids. Outside Singapore, the UK and the US, the grid factors are Ember-derived approximations, as flagged above.

None of this makes the estimate useless. It makes it what it says on the tin: a first number, produced from real bills and published factors, that tells you where the weight sits before you spend money measuring the rest.

Where this fits in your reporting

Electricity here is Scope 2; gas and diesel are Scope 1 — the two scopes every framework starts with, whether it's IFRS S2, GRI 305, a CDP questionnaire, or a national code, and the arithmetic is identical for a company, a nonprofit, a school, or a public agency. Singapore layers a published deadline on top: all SGX-listed issuers must report Scope 1 and 2 from FY2025, and listed customers push the same ask down their supply chains well before that timeline reaches a supplier directly.

When one of those questionnaires lands, this calculation — bills times published factors — is exactly the shape of answer being requested.

The cheapest habit is to start monthly, not annually. When you would rather not type the numbers in, upload the bills themselves — the same factors get applied to figures read straight off the PDF, with a confidence score on every extracted field, no signup required, and files deleted after 30 days.

Sources

• Energy Market Authority, Singapore Energy Statistics — grid emission factor tables (Singapore Open Data Licence): ema.gov.sg/resources/singapore-energy-statistics
• UK Government, Greenhouse gas reporting: conversion factors 2025 (Open Government Licence v3.0): gov.uk/government/collections/government-conversion-factors-for-company-reporting
• US EPA, eGRID — US grid emission factors (public domain): epa.gov/egrid
• Ember, Yearly Electricity Data — country grid intensities (CC-BY): ember-energy.org
• GHG Protocol, Corporate Standard and Scope 2 Guidance — scope definitions and methods: ghgprotocol.org
• SGX RegCo — climate reporting requirements and listing rules 711A/711B: sgx.com/regulation