A helicopter emissions calculation is only as good as the fuel figure underneath it.
If you know how much fuel the helicopter actually used, the calculation is straightforward. If you don’t, we have to estimate fuel burn from the aircraft and the information available about the journey.
That gives the calculator a simple hierarchy: measured fuel first, airborne time second, route modelling only where the published evidence supports it.
This page sets out exactly how we do that. If you want to work out a journey rather than read about the method, use the helicopter carbon calculator.
Version 1.1. Published 20 August 2026, revised 8 September 2026. Emission factors: 2026.
Every calculation records the factor year it used. If you return to a certificate in three years’ time, we can still explain which figures produced it.
Three ways we calculate helicopter emissions
The calculator uses the strongest information you can provide.
| What you know | How we calculate the journey | Result |
|---|---|---|
| Actual fuel used | Apply the published Government emission factor directly to the fuel consumed | High confidence |
| Airborne time | Multiply lift-off-to-touchdown time by the published fuel rate for that aircraft | Modelled estimate |
| Route only | Model start-up, take-off, climb, cruise, descent, landing and shutdown | Indicative estimate |
If you have the actual fuel figure, use it. That removes the aircraft fuel-burn model completely, and the helicopter carbon calculator will accept it in litres or kilograms.
Most passengers and charter clients won’t have it. Airborne time is therefore the next best input.
Route-only calculations are available for five aircraft where we have a published flight-phase model. We don’t manufacture a route estimate for the others.
The emission factors we use
We use the 2026 UK Government greenhouse gas conversion factors for company reporting, published by the Department for Energy Security and Net Zero. View the publication
The calculator includes both the emissions from burning the fuel and the emissions from producing and delivering it.
| Fuel | Combustion | Production and delivery | Total per litre |
|---|---|---|---|
| Aviation turbine fuel | 2.54269 kg CO2e | 0.52817 kg CO2e | 3.07086 kg CO2e |
| Aviation spirit | 2.33116 kg CO2e | 0.61425 kg CO2e | 2.94541 kg CO2e |
For jet fuel, including production and delivery adds about 21% to the figure compared with counting combustion alone.
Jet fuel has to be extracted, refined and transported before it reaches the aircraft. Those emissions happened, so we count them.
Litres and kilograms are kept separate
The Government workbook publishes factors per litre and per tonne.
We use the factor matching the unit in which the fuel data was supplied. We don’t take the litres figure and derive the tonnes figure ourselves, or vice versa.
Converting between them would mean assuming a fuel density, and the Government’s own jet-fuel figures imply densities that differ by about 0.24% depending on which direction you calculate. Both sets are published, so we use the published one.
Where our helicopter fuel-burn figures come from
The calculator currently contains 29 helicopter entries.
They are not all the same kind of record, and what the calculator will do for you depends on which kind yours is:
- Twenty-three have a published fuel rate in gallons per airborne hour. They answer “how long were you in the air”, and they decline the route.
- Five can also be worked out from the route alone, because published research gives them a flight profile as well as a cruise fuel flow. All five have a published hourly rate too.
- One, the Bell 407GXi, is listed and deliberately answers nothing. There is a section on it below.
The source determines what the calculator can sensibly do.
Twenty-three aircraft with a published hourly fuel rate
The US Department of the Interior contracts helicopters for government operations and publishes expected fuel consumption in US gallons per flight hour.
Crucially, its contract also defines what it means by a flight hour: lift-off to touchdown. The aircraft hour meter is required to record the same period. View the contract schedules
That gives us a fuel rate and a time measurement using the same clock.
| Aircraft | US gallons per airborne hour |
|---|---|
| Leonardo AW139 | 140 |
| Eurocopter EC 155 B1 | 95 |
| Sikorsky S-76C++ | 94 |
| Sikorsky S-76C+ | 90 |
| Aerospatiale SA 365 N1 / AS 365 N1 Dauphin | 87 |
| Airbus H145 D2 | 83 |
| Eurocopter EC145 (older, BK117 C-2) | 80 |
| MBB BK 117 (A and B series) | 77 |
| Bell 429 GlobalRanger | 73 |
| Leonardo A109 / AW109 | 72 |
| Leonardo A119 / AW119 Koala | 70 |
| Eurocopter EC135 / H135 | 64 |
| Aerospatiale AS 355 F1 / F2 Ecureuil 2 | 58 |
| Airbus H125 / AS350 B3 | 50 |
| Aerospatiale AS 350 B1 Ecureuil | 46 |
| Aerospatiale AS 350 B / BA Ecureuil | 45 |
| Bell 505 Jet Ranger X | 39 |
| Bell 206L-3 or L-4 LongRanger | 38 |
| Bell 206L-1 LongRanger | 32 |
| Bell 206B-III JetRanger III | 27 |
| Bell 206B-II JetRanger II | 25 |
| Robinson R66 Turbine | 24 |
| Robinson R44 and R44 II | 15 |
Two of those rows come from somewhere else, and we say so rather than rounding the description up. The Sikorsky S-76C++ figure is from the US Forest Service helicopter services chart, not the Interior contract. The Airbus H145 D2 figure is from a different Interior contract, the L-48 On-Call Small Helicopters schedule, and it was then checked against the Forest Service chart, which gives the same 83. Both of those contracts define the flight hour the same way as the Alaska one does.
These are operational averages, not measurements from your particular flight. The published schedule does not tell us the payload or weather for an individual sector.
We therefore label calculations based on these rates as modelled estimates.
If you flew one of these aircraft and know the airborne time, we can calculate from it. Choose the aircraft and enter the time in the helicopter carbon calculator.
If all you know is the route, we stop there. A fuel rate of 140 gallons an hour doesn’t tell us whether your AW139 took 24 minutes or 37 minutes to make the journey.
Five aircraft we can model from the route
Route-only estimates are available for these five. The middle column is the part worth reading.
| Aircraft | How the cruise fuel flow was arrived at | US gallons per airborne hour |
|---|---|---|
| Bell 407 | The Bell flight manual figure, reproduced in the research | 45 |
| Aerospatiale AS350 B2 Ecureuil | Scaled from the Bell 407, on two cruise points at 4,000 lb | 48 |
| Eurocopter EC130 B4 | Scaled from the Bell 407, on two cruise points at 4,000 lb | 53 |
| Bell 206L LongRanger (version not known) | Scaled from the Bell 407, on two cruise points at 4,000 lb | 38 |
| Eurocopter EC120 B Colibri | Scaled from the Bell 407, on two cruise points that the research itself extrapolated | 31 |
Only the Bell 407 rests on a manufacturer’s own flight manual figure. The other four are scaled from it. The EC120 B is scaled from cruise points that the research extrapolated rather than read from a manual, which makes it the weakest record in the library, and the calculator grades it accordingly on screen.
These use a 2011 FAA-sponsored research report on modelling helicopter fuel consumption. View the report
Instead of treating the entire journey as cruise, the model divides the flight into start-up, take-off, climb, cruise, descent, landing and shutdown.
That gives us enough information to estimate a journey when only the start and destination are known.
We label every one of these results indicative.
The right-hand column is the published hourly rate for the same aircraft, from the Interior contract. If you know your airborne time, the calculator uses that rate instead of the route model, because a time you measured beats a journey we inferred.
One aircraft that is listed and answers nothing
The Bell 407GXi appears in the list and produces no aircraft-modelled calculation at all.
That is deliberate. The Bell 407 figures in this library describe the earlier aircraft, with the Rolls-Royce 250-C47B engine. The 407GXi has a different engine, the M250-C47E/4. Handing it the older aircraft’s fuel rate would be a guess dressed as a figure, so it is refused by name instead, and the calculator says so on screen.
If you know the fuel your 407GXi actually used, enter that. The calculation then needs no aircraft rate at all.
Where route-only estimates are weakest
The weakest part of the route model is the fuel used outside cruise: starting up, taking off, hovering, climbing, descending, landing and shutting down.
The FAA-sponsored report is unusually useful because it says exactly where its own evidence runs out. It found no published source giving measured fuel use for each of these phases across different helicopters, so those phase values had to be assumed. The report recommends replacing them with flight-test data and had actual operational data from only one operation.
I wouldn’t describe that as high-confidence evidence, and we don’t.
On a long flight, cruise dominates the calculation. On a fifteen-minute helicopter transfer, start-up, climb, descent and landing can account for a substantial share of the journey.
So every calculation built from the route alone is labelled indicative estimate.
The useful next step is not another theoretical model. It is real operating data.
We are interested in fuel used and airborne time from 30 to 50 completed journeys for each exact aircraft variant. With enough operator records, we can test the published model against what helicopters actually do.
How we avoid double-counting climb and descent
There is an easy mistake to make when building a flight-phase model.
Suppose the helicopter covers part of its route while climbing and another part while descending. If you calculate fuel for those phases and then calculate cruise fuel across the entire route distance, you have charged for those kilometres twice.
The shorter the journey, the larger that error becomes.
Our calculator first calculates the distance covered during climb and descent. It subtracts both from the route distance and applies the cruise calculation only to what remains.
That behaviour is also covered by the calculator’s tests.
How we handle wider warming effects at altitude
Aviation can cause warming beyond the carbon dioxide released by burning fuel, including effects involving nitrogen oxides and vapour trails.
The UK Government provides a 1.7 multiplier for aviation and recommends its use because of these wider effects.
There is a problem when applying it to helicopters: the evidence behind that multiplier comes from aeroplane aviation, not helicopter operations.
Helicopters generally fly much lower and operate very differently.
I don’t think quietly folding an aeroplane-derived multiplier into the headline helicopter figure is defensible. I also wouldn’t claim that helicopters have no wider atmospheric effects simply because they normally fly lower. We don’t have evidence for that either.
So we show the Government-based calculation separately. Both numbers are in front of you, and you can apply the adjustment or set it aside according to your own reporting.
How the 1.7 multiplier is calculated
The multiplier applies to the carbon dioxide component, not to methane, nitrous oxide or the emissions from producing and transporting the fuel.
The additional amount is therefore CO2 × 0.7.
We don’t add the original CO2 again. Doing that would count it twice.
For helicopters using aviation spirit rather than jet fuel, we don’t apply the multiplier because the Government publishes the aviation adjustment for jet fuel. Extending it to another fuel would be our assumption.
This also explains why our main emissions figure may be lower than a calculator that simply builds the full 1.7 multiplier into its headline number.
What the calculator will not infer
Some inputs look close enough to convert. In practice, they aren’t.
We don’t convert one type of flight time into another
Airborne time, block time, rotors-running time, Hobbs time and billed time can all describe different periods.
On a short helicopter journey, the difference may include several minutes of fuel burn.
If our fuel rate is defined from lift-off to touchdown and your invoice gives block time, we don’t invent a conversion between the two.
We ask for airborne time or actual fuel instead.
We don’t produce route estimates without a flight-phase model
Only five of the 29 aircraft entries currently support route-only calculation.
The remaining aircraft either require airborne time or, in the case of the Bell 407GXi, actual fuel data.
We don’t substitute another aircraft’s fuel rate
The Bell 407GXi is not treated as a Bell 407.
It has a different engine and other substantial changes. Until we have fuel data that properly applies to the GXi, the calculator won’t produce an aircraft-modelled result for it.
A precise-looking number based on the wrong aircraft isn’t an improvement.
We don’t derive an aviation-spirit density
The Government’s litre and mass figures for aviation spirit imply different densities.
Rather than choose one ourselves, we use the Government factor matching the unit supplied.
We don’t store your landing locations
A helicopter journey may begin or end at a private estate, hotel, hospital or another location you have no reason to place permanently in our records.
The calculator uses the two locations to calculate a distance. After that conversion, the locations themselves are not carried into the payment, receipt, certificate or failed-calculation record.
The system stores the journey distance, not your two places.
How the climate contribution is priced
The contribution is calculated from the fullest emissions figure supported by the published evidence.
For jet-fuel calculations, that includes the separately calculated wider atmospheric effect. Where we don’t have a published basis for that addition, we use the lifecycle fuel total alone.
We made that choice deliberately.
If we calculated the emissions one way but charged against a smaller number simply because that number happened to be displayed more prominently on the page, the amount funded would depend on page design rather than methodology.
I wouldn’t defend that. The same quantity of warming is funded at the same rate, whichever aircraft and fuel produced it.
The current price is £26.25 per tonne before VAT.
Money is rounded to two decimal places at each step, with a minimum charge of £0.50.
A worked example, end to end
One hour of airborne time in a Leonardo AW139. This is the middle of the three routes: a published fuel rate and a time you can read off the aircraft.
Every figure below comes from a source named on this page, so you can check the whole thing yourself.
| Step | The arithmetic | Result |
|---|---|---|
| Published fuel rate | AW139, US Department of the Interior schedule | 140 US gallons per airborne hour |
| Converted to litres | 140 × 3.785411784 | 529.95765 litres |
| Burning the fuel | 529.95765 × 2.54269 | 1,347.52 kg CO2e |
| Producing and delivering it | 529.95765 × 0.52817 | 279.91 kg CO2e |
| Lifecycle total | 529.95765 × 3.07086 | 1,627.43 kg CO2e |
| Carbon dioxide component alone | 529.95765 × 2.51973 | 1,335.35 kg |
| Wider atmospheric effect | 1,335.35 × 0.7 | 934.75 kg CO2e |
| Both figures added | 1,627.43 + 934.75 | 2,562.18 kg CO2e |
| Contribution | 2.56218 tonnes × £26.25 | £67.26 before VAT |
The calculator labels this result a modelled estimate. A rate of 140 gallons an hour is an operational average across many flights, not a measurement of the one you took.
Notice that the wider atmospheric effect is more than half as large again as the fuel figure it sits beside. That is exactly why we show it as its own line rather than folding it in.
What your contribution means
The calculation tells you the estimated climate impact of the helicopter journey according to the methodology above.
If you choose to make a contribution, your payment funds carbon projects supported by C Level and you receive a certificate recording the amount and the calculation used. Both start from a journey worked out in the helicopter carbon calculator.
The contribution doesn’t alter how much fuel the helicopter burned. It also doesn’t remove those emissions from your organisation’s own greenhouse-gas inventory. Your travel emissions and your support for a carbon project are separate things.
For the same reason, we don’t describe the flight as carbon neutral on the strength of the contribution.
Carbon projects also produce different kinds of outcomes. Avoiding an emission, reducing an emission and removing carbon dioxide from the atmosphere are not interchangeable terms, and we don’t use them as though they were.
Frequently asked questions
Why does your helicopter emissions figure differ from another calculator?
Check the calculation boundary first.
We include emissions from producing and delivering the fuel as well as burning it. For jet fuel, that increases the lifecycle fuel figure by about 21% compared with combustion alone.
We also show the Government’s wider aviation effect separately rather than automatically folding it into the headline figure.
For route-only calculations, we model the phases of the flight rather than treating every kilometre as cruise.
Can I use the result for company emissions reporting?
The calculation records its methodology, input basis and factor year, so you can provide it to whoever is responsible for your reporting.
Whether it should be used directly in your company’s greenhouse-gas inventory depends on the reporting framework and your auditor or adviser.
My invoice says the flight took one hour and forty minutes. Can I use that?
Only if you know what the time represents.
If your operator confirms that it is airborne time from lift-off to touchdown, use it.
If it is block time, rotors-running time or billed time, don’t enter it as airborne time. Ask the operator for the airborne time or actual fuel used instead.
What if my helicopter isn’t listed?
If you know the actual fuel used, the calculator doesn’t need an aircraft-specific fuel rate. Enter the fuel in the helicopter carbon calculator and the aircraft doesn’t matter.
If you don’t know the fuel used and your exact helicopter variant isn’t supported, tell us which aircraft it is. We can add it when we have a source we are prepared to use.
Can helicopter operators use the calculator with their own clients?
Yes.
We are developing a partner version for helicopter operators, brokers and other aviation businesses that want to make the calculator available to their clients.
You don’t need to make a carbon-neutral claim or sell carbon credits yourself. The calculator, methodology, payment and certificate can remain with C Level.
If you’d like to use it with your customers, get in touch.
Sources
Four published sources sit underneath every figure on this page. All four are free to read, and we have given the exact documents rather than the front doors, so you can go straight to the numbers.
UK Government greenhouse gas reporting conversion factors, 2026. Department for Energy Security and Net Zero. The workbook ghg-conversion-factors-2026-full-set.xlsx, sheets “Fuels” and “WTT- fuels”. This supplies both fuel factors and the 1.7 aviation multiplier. https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2026
United States Department of the Interior, Office of Aviation Services — helicopter contract schedules. Fuel consumption in US gallons per flight hour, with flight time defined lift-off to touchdown and the hour meter required to record the same period. This supplies twenty-one of the twenty-three published fuel rates, from the Alaska On-Call schedule, plus the Airbus H145 D2 rate from the L-48 On-Call Small Helicopters schedule. Contracts index: https://ibc.doi.gov/acquisition/aviation/customer/contracts The schedule we read: https://ibc.doi.gov/sites/default/files/AQD/aviation/Master-AK-Helo-On-Call-contract-Section%20A-C.pdf
United States Forest Service, National Interagency Fire Center – helicopter services hourly flight rates and fuel consumption chart. Helicopter Support Services solicitation 1202SA21R9008, Attachment 10, revision of 6 May 2022. This supplies the Sikorsky S-76C++ rate, and it is the second reading of the Airbus H145 D2 rate. The copy we obtained was a procurement mirror rather than a Forest Service host, so it was checked against the February 2019 edition of the same chart from an archive of fs.usda.gov, which agrees on every shared row.
Helicopter fuel burn modelling in AEDT, 2011. Research sponsored by the United States Federal Aviation Administration, report DOT-VNTSC-FAA-11-09, by the Volpe National Transportation Systems Center. This supplies the cruise fuel flows, the flight-phase multipliers and the reference flight profile behind the five route-only aircraft. It also supplies the aircraft flight manual performance data for those five types. Record: https://rosap.ntl.bts.gov/view/dot/9351 Full report: https://rosap.ntl.bts.gov/view/dot/9351/dot_9351_DS1.pdf
Version control
This is methodology version 1.1, published on 20 August 2026 and revised on 8 September 2026.
What changed in version 1.1. The aircraft list, and nothing else. Version 1.0 described 19 entries, of which 13 had a published hourly rate. The calculator now offers 29, of which 23 have one. The tables above are built from the calculator’s own aircraft library rather than retyped; the two rates that do not come from the Interior contract are named; the way each of the five route-modelled cruise figures was arrived at is stated aircraft by aircraft; and the Bell 407GXi has a section explaining why it answers nothing. No emission factor changed, and no calculation changed.
When Government emission factors change, aircraft data is added or better operational evidence replaces an assumption, we update the version and publication date.
Existing calculation records retain the methodology and factor year used when they were created.
If you spot an error in the calculation or the published working, please tell us. We want the methodology to be checkable because that is how it gets better.