The one rule
Funding a project does not reduce the emissions figure.
The calculation and the contribution remain separate in the result, the business report and the certificate journey.
Business, flight and helicopter carbon calculators
All three calculators use the UK Government’s 2026 conversion factors. You can see the calculation before deciding whether to fund a carbon project. No account is required.
Business Carbon Calculator
Answer a short set of questions about premises energy, business travel, commuting, waste, water and refrigerants. The calculator returns a footprint across Scope 1, Scope 2 and Scope 3, and shows the working line by line.
It says plainly what it has not measured. A source you cannot answer is recorded as unquantified rather than counted as zero, and it is listed with the result. For a manufacturer or a retailer, that stated gap is usually the largest part of the footprint, and it is the reason to talk to us.
The report is a dated document you download and keep. Every line names the UK Government factor behind it. Nothing is stored, nothing is sent, and no account is needed.
Flight Carbon Calculator
Enter the departure and arrival airports, passenger numbers and cabin class. The calculator handles one-way, return and multi-leg journeys, then shows the distance, emissions factor and estimated CO₂e.
For business travel, you can request a dated PDF recording the journey, CO₂e result, emissions factors, calculation method and version. You do not have to fund a project to receive the report.
Helicopter Carbon Calculator
Choose the aircraft and enter the fuel actually burned, the recorded flight time or the route. Actual fuel gives the best available calculation. The current interface contains 19 aircraft and variant entries; five can be estimated from the route alone.
The calculator separates fuel combustion from producing and delivering the fuel. It also shows what was supplied, what was estimated and how confident we are in the result. Positioning flights are included when you enter them, rather than guessed.
A flight emissions report your business can keep
The flight calculator can email you a dated PDF for a single journey. It records:
- the route and passenger details;
- the gross CO₂e result;
- the emissions factors used;
- the calculation method and version.
You do not have to fund a project to request the report. If you do choose to fund one, businesses can pay by invoice with 30 days to pay.
Working out a year of travel?
If you are measuring a whole travel programme rather than a single journey, we can look at the year as a portfolio: what to measure, which projects to fund and what your reporting needs to say.
Talk about a portfolio or read how our carbon footprint consultancy works
Put a carbon calculation inside your own system
There are three practical routes. The right one depends on where the calculation needs to appear, what data you already hold and what the user should receive afterwards.
One difference matters before you choose. The first two routes use the rebuilt calculators shown above, on UK Government 2026 factors. The API does not: it runs the older calculation, and it returns a priced quote together with the carbon figure rather than the figure on its own. We say so again beside that route, and we will confirm exactly what it does before you build anything on it.
Hosted calculator
Send people to a hosted calculator
Link directly to the C Level flight or helicopter calculator. We host and maintain the page; there is nothing for your development team to build.
Suitable when the calculation can sit on a C Level page and you only need to point people at it.
Your developers only add a link.
Embedded component
Add a calculator to your website or portal
The rebuilt calculators are lightweight JavaScript components. We can scope an embedded version for a booking journey, customer portal or internal reporting tool.
Before quoting, we agree the calculation, hosting, visual treatment, data passed into the tool and what the user receives from it.
Your developers add a small piece of code to a page.
API integration
Carbon calculator API integration
We run a REST API and have built C Level calculations into other organisations’ systems. The published v1 definition contains routes for emissions calculations, airport and city lookup, project lookup, quotes, purchases and certificate status.
As set out above, this route runs the older calculation and returns a priced quote together with the carbon figure. The fields beside this are the real v1 request and response, taken from the published definition. The values are zeros because we have not run the route with a working key, and we will not print a figure we have not seen.
New API access is not self-service. We are reviewing the existing routes against the rebuilt calculation engines before making new promises about them. We will confirm the method, inputs, outputs and transaction path with you before anything is built.
Your developers write against our interface.
What we need to scope an integration
Tell us:
- what activity you need to calculate;
- where the input data comes from;
- where the result needs to appear;
- whether you need a calculation only, or project funding and a certificate as well;
- the expected volume and proposed launch date.
We can then tell you whether to use a hosted calculator, an embedded component or an API connection, and what work is required.
What a new carbon calculation should show
A carbon number should not arrive as a black box. For a new integration, we agree the following before implementation:
- what the calculation includes and excludes;
- the emissions factors, source and year;
- which values came from the user and which were modelled;
- the assumptions and uncertainty that affect the result;
- the gross CO₂e before any project funding is discussed.
Funding a project does not reduce the emissions figure. The calculation and the contribution remain separate in the result, the business report and the certificate journey. The full method, including where we have corrected it, is set out on the flight calculator page.
If you want the measurement done rather than built, our carbon footprint consultancy covers Scope 1, 2 and 3.
We have been calculating carbon footprints since 2000
C Level started in 2000. Since then we have built public calculators, customer journeys, business reports, payment flows and certificates.
The software has changed. The work has not: set the boundary, use a factor you can trace, show the assumptions and keep the carbon number separate from what the customer chooses to fund.
Carbon calculator API questions
What is a carbon calculator API?
A carbon calculator API allows one system to send activity data to a calculation service and receive a structured result. The input might be a journey, fuel use or electricity consumption. The exact boundary, factors, units and output must be agreed before integration.
How do I get API access?
New API work begins with a technical scoping conversation, so we can confirm the calculation method, data, output and support required. Keys are not issued online.
Can I integrate the helicopter calculator?
Helicopter integrations are scoped individually. The live helicopter calculator is not part of the published v1 API. Use the hosted calculator now, or tell us your case and we will scope it.
Can I embed a C Level calculator instead of using the API?
Yes. The rebuilt flight and helicopter calculators use lightweight JavaScript components. We can scope how one would sit inside your website or portal without requiring your users to visit a separate C Level page.
Can I receive a flight emissions result without funding a project?
Yes. The live flight calculator shows the gross CO₂e before project funding and can email a dated business emissions report without a purchase.
Start here
Tell us where the calculation needs to appear
Describe what you need to calculate, where the input data comes from and what the user should receive. We will tell you which integration route fits and what needs to happen next.
Or use a calculator now: use the Flight Carbon Calculator, or use the Helicopter Carbon Calculator.