Everyone has a carbon footprint, and almost nobody knows what’s in theirs. The phrase gets thrown around in ads, apps and airline checkouts until it sounds like a single, precise number stamped on your life. It isn’t. A footprint is an estimate: a set of activities, multiplied by emission factors, added up. Knowing how that math works is the difference between a number you can act on and a number that just makes you feel guilty.
What a footprint is
Your carbon footprint is the greenhouse gas released because of the things you do in a year: heating and powering your home, getting around, flying, eating, and, increasingly, the computing you lean on every day. Each activity gets converted into a common unit, usually kilograms or tonnes of carbon dioxide (or “CO₂-equivalent,” which folds other gases into the same scale).
The conversion step is where most of the meaning lives. A kilowatt-hour of electricity isn’t the same everywhere. A gallon of gasoline burns the same chemistry everywhere, but how many gallons you use depends on your car and your commute. A footprint is only as good as the activity data you give it and the factors it applies.
That’s why we built our calculator around a handful of inputs you actually know, like your power bill, your miles and your flights, instead of a hundred lifestyle questions you’d have to guess at.
How our calculator measures it
The calculator walks through five areas:
- Home. Electricity and natural gas use. Electricity is converted with a U.S. average grid emission rate from the EPA’s eGRID data, and gas with the EPA’s combustion factor. Both are listed, with links, at the bottom of the calculator page.
- Transport. Miles driven and your car’s fuel economy, turned into gallons and then into CO₂ using the EPA’s per-gallon figure for gasoline.
- Flights. Short, medium and long trips, each with its own per-passenger-mile factor from the EPA’s emission factors hub.
- Diet. A choice between broad diet types, based on a peer-reviewed study of the dietary emissions of meat-eaters, fish-eaters, vegetarians and vegans.
- Cloud and AI. Chatbot prompts and hours of video streaming.
Every factor we use is cited on the calculator itself. We’d rather show our work than ask you to trust a black box.
The AI line item, and why it’s tiny for you
The fifth category is the one people ask about most, so here are the numbers behind it.
Google says that by its own comprehensive method, the median Gemini Apps text prompt uses 0.24 watt-hours of energy and emits 0.03 grams of CO₂-equivalent. Google also notes in the same post that the data and claims have not been verified by an independent third party. That’s worth remembering. It’s a company grading its own homework, and it describes a median text prompt, not image generation, video, or long reasoning sessions.
Streaming is similar. The IEA’s fact-check of viral streaming claims put a typical hour of streaming video in 2019 at around 0.077 kWh of electricity, and found that devices account for about 72% of that energy, data transmission 23%, and data centres just 5%. Your TV is a bigger factor than the server farm.
So for most individuals, the AI and streaming row of the calculator will be a rounding error next to driving or one cross-country flight. That’s the honest answer, and we show it.
Small per click, huge in aggregate
But “tiny for you” is not the same as “tiny.” The same IEA analysis warned that efficiency gains may be unable to keep pace with growing data demand, naming AI among the emerging technologies driving it. That was written in 2020, before the current buildout.
A fraction of a gram per prompt, multiplied across billions of prompts and the new data centers being permitted to serve them, adds up to grid-scale demand. That’s a policy and infrastructure problem, not a personal-guilt problem, and it’s why we cover it on our data-centers page. Your footprint measures what you control. The buildout is about what we decide collectively.
What the calculator leaves out
We’d rather be upfront about the limits:
- Energy and travel are counted as CO₂ only. Other gases from these sources aren’t added.
- Flights get no extra multiplier for high-altitude warming effects, so the flight number is likely conservative.
- Stuff isn’t counted. Clothes, electronics and other things you buy carry emissions from manufacturing that we don’t estimate.
- Grid factors are national averages. If your utility is much cleaner or dirtier than average, your home number will be off.
None of these make the number useless. They make it a floor, not a ceiling.
What to do with your number
A footprint is useful for two things: finding your biggest line item and tracking whether it shrinks. For most people that’s driving, flying, or home energy. Cut there first. A heat pump or one fewer long-haul trip will do more than any amount of deleting old emails.
For what’s left, the calculator shows how many credits would cover it at one credit per tonne, and lets you browse projects. To be clear, that part is a prototype. The projects and prices are mock-ups, and no real credits are sold or retired. We’re building it in the open so that when real credits do arrive, the flow is honest about what each one represents. In the coming weeks we’ll cover how to tell a real offset from a weak one, and why removal costs more than avoidance.
Find your biggest line item. Calculate your footprint. It takes about three minutes.