Carbon offsetting you can check: every credit is retired in a public registry.

Methodology

How our calculators work

What each calculator asks, how it adds up your answers and where its numbers come from.

What every calculator does

Set questions

Each calculator asks a fixed list of questions. Some only appear when they apply, such as air conditioning when you stay somewhere hot. Pick an answer or type it in your own words.

Code does the maths

When you type an answer, an AI only works out which option you mean. Code then does every calculation, the same way each time. The form mode uses no AI at all.

Published emission factors

Most figures are an amount of activity times a published emission factor, mainly the UK government’s 2026 conversion factors (DEFRA), Ember’s electricity data and Our World in Data.

Estimates, not audits

Results come with a range of ±10%. They are estimates to help you decide what to reduce and what to offset, not an audited greenhouse gas inventory.

What the calculators share

Flights

Distance is the straight line between the airports. Per passenger-km in economy: 0.229 kg CO₂e under 463 km, 0.126 kg up to 3,700 km and 0.117 kg beyond (DEFRA 2026). These include the extra warming from contrails and other non-CO₂ effects, about 1.7 times the CO₂ alone. A business-class seat on a long flight counts 2.9 times economy.

Electricity

Each country’s grid intensity from Ember, in kg CO₂e per kWh (2025 data). Where the country isn’t known, the world average: 0.458 kg.

Food

Per person per month, by diet, from Our World in Data (Poore & Nemecek): vegan 45 kg, vegetarian 90 kg, omnivore 120 kg and meat-heavy 180 kg CO₂e.

Shopping and waste

Coffset’s own screening estimates, per person per month: shopping 30 to 220 kg and waste 10 to 40 kg CO₂e.

Each calculator

My lifestyle

Result
A monthly figure for your household, and per person.
What it asks
Country, people at home, home size, heating, solar panels, car and daily distance, public transport, flights a year, diet, shopping, waste and screen time.
How it adds up
  • Home: electricity by home size (2,400 to 11,500 kWh a year, IEA), less what solar panels make (1,200 kWh per kW a year), times your country’s grid. Heating by fuel and home size: gas heating comes to 2,090 kg a year for a medium home.
  • Car: kilometres a day × 30 days × the car’s factor (petrol 0.162 kg per km, DEFRA 2026); an electric car uses the grid. Flights: 252 kg for each short return flight and 1,872 kg for each long one.
  • Food, shopping and waste per person, times the people at home.
What it leaves out
It doesn’t read your energy bills. Countries that aren’t in the list use the world-average electricity figure.
Open the calculator

A trip

Result
One figure for the whole trip, and per traveller.
What it asks
Travellers, how you travel (plane, train, coach, car, cruise or a mix), the route or distance, cabin class, return or one way, connections, nights away, where you stay and activities.
How it adds up
  • Flights: distance × the flight factor × cabin class × travellers, twice for a return. With connections, the distance counts once for each flight.
  • Over land and sea, per km: train 0.031 kg and coach 0.039 kg per passenger, car 0.162 kg for the whole car, cruise 0.25 kg per passenger (an estimate: DEFRA has no cruise figure).
  • Hotels: nights × rooms (two people a room) × the hotel type, 25 kg a night for a standard hotel (Cornell 2024). Activities: a rough amount per person per day.
What it leaves out
Distances are straight lines, without detours. The activity figures are rough estimates.
Open the calculator

An event

Result
One figure for the event, and per attendee.
What it asks
Type of event, country, number of attendees, how far they travel, venue size and days, catering and production.
How it adds up
  • Travel: each attendee’s round trip by distance band: local 8 kg, regional 39 kg, national 252 kg and international 756 kg (DEFRA 2026 car, train and flight factors).
  • Venue: m² × days × 1.1 kWh per m² a day × the country’s grid.
  • Catering: attendees × plates per person for the type of event × 1.2 to 5 kg a plate (Our World in Data). Production (stage, sound, lights): a set amount by scale, 50 to 6,000 kg.
What it leaves out
Travel uses distance bands, not each guest’s real journey. Guests’ hotel nights aren’t counted.
Open the calculator

My business

Result
A monthly figure for the company, split into Scope 1, 2 and 3, and per employee.
What it asks
Country, sector, employees, electricity, gas, company vehicles, business flights, commuting, and a few questions for your sector, such as cloud spend, goods bought, refrigeration, freight or raw materials.
How it adds up
  • Scope 2: the electricity you enter, or 215 kWh a year per m² of office (Carbon Trust), or 220 kWh a month per employee, times the grid.
  • Scope 1: gas (DEFRA 2026), company vehicles (km × DEFRA 2026 vehicle factors), refrigerant leaks (EU F-gas Regulation) and machinery fuel.
  • Scope 3: flights (1,500 km and 8,000 km each way), commuting (21 working days a month) and purchases by spend (US EPA factors).
What it leaves out
It is a screening estimate, not a GHG Protocol, CSRD or ISO 14064 inventory. Spend is converted with factors per US dollar.
Open the calculator

Digital nomads

Result
A monthly figure for your year on the road.
What it asks
Home, if you have one; the places you stay this year and for how long; where you stay; air conditioning; trains or planes between places; trips home and weekends away; cabin class; where you work; video calls; how you get around; diet; shopping; and how often you replace your laptop and phone.
How it adds up
  • Moving: the year is a loop from home (or your first place) through each place and back. Each move is a flight, priced by distance (DEFRA 2026), or a train, coach or ferry if you take one and the trip is a day or less.
  • Staying: hotels by country (DEFRA 2026); a flat uses 200 kWh of electricity a month, plus air conditioning in hot places, times that country’s grid (Ember). Heating where it’s cold, from each city’s heating degree days (NASA POWER).
  • Working and living: coworking 7.2 kWh a day, working from home 0.022 kg an hour (DEFRA 2026), video calls 0.4 kg an hour, getting around, food, shopping, and your laptop and phone (250 and 70 kg to make) spread over the years you keep them.
What it leaves out
Distances are straight lines and stopovers aren’t added, so routes with connections count a little low. Heating is spread evenly over the year. Everything is for one person.
Open the calculator

From result to price

Carbon credits cost €0.04 per kg CO₂e (€40 a tonne). A monthly result can be covered with a monthly subscription, which is 10% cheaper and can be cancelled at any time, or paid once. A trip or an event is one payment. You always see the exact amount before you pay.

Sources

Emission factors version v2-2026-10.

Read our general methodology