How accurate is the home energy estimate?

It's a simplified per-resident average, not based on your actual utility bill.

Why do flights have such a big impact per trip?

Aviation burns fuel very intensively per passenger-mile, with an outsized atmospheric warming effect.

Where do the diet figures come from?

Scarborough et al. (2014), a peer-reviewed study of the EPIC-Oxford UK cohort.

Does this include emissions from things I buy?

No — consumer goods, services, and waste aren't modeled here.

Can I use this to compare a metric or imperial vehicle?

Enter your vehicle's combined mpg rating — the car emissions factor is calibrated to gallons of gasoline.

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Math & Everyday

Carbon Footprint Calculator

Estimated annual household CO2e from home energy, driving, flights, and diet.

🔒 Runs entirely in your browser — nothing here is ever uploaded

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About the Carbon Footprint Calculator

Estimates a household's annual carbon footprint (CO2e) across four major lifestyle categories — home energy, car travel, air travel, and diet — compared against a commonly cited US per-person average, using published emissions factors for each category.

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How to use it

Enter your household size.
Enter annual household miles driven and your vehicle's combined fuel economy.
Enter your short-haul and long-haul flights per year.
Select your household's typical diet type.
Read your estimated total and per-person annual footprint, compared to the US average.

Formula

Home energy = 2.3 tonnes CO2e × household size. Car = (annual miles ÷ mpg) × 8.887 kg CO2 per gallon ÷ 1000. Flights = (short-haul × 0.2t) + (long-haul × 1.75t) per passenger. Diet = a per-person annual figure by diet type × household size. Total = sum of all four categories.

Worked example

A 2-person household driving 12,000 miles/year at 28 mpg, taking 2 short-haul and 1 long-haul flight, on an average diet: about 14.56 tonnes CO2e total, or 7.28 tonnes per person.

Emissions factors used

Emissions factors used
Category	Factor	Source basis
Car (gasoline)	8.887 kg CO2 / gallon	EPA exact combustion figure
Short-haul flight	~0.2 t CO2e / passenger	Commonly cited per-flight average
Long-haul flight	~1.75 t CO2e / passenger	Commonly cited per-flight average
Meat-heavy diet	~2.6 t CO2e / year	Scarborough et al. 2014, annualized
Vegan diet	~1.05 t CO2e / year	Scarborough et al. 2014, annualized

Interpreting your result

This is a simplified, illustrative estimate covering four major categories — it doesn't capture every emissions source (consumer goods, waste, indirect service emissions). Diet figures are annualized from a peer-reviewed UK cohort study (Scarborough et al., 2014).

Recommendations

• Diet and car travel are typically the two most controllable categories for most households.
• Long-haul flights carry an outsized impact — a single round trip can rival months of typical car commuting emissions.
• This tool's 4-category scope will generally read well below a 'full' national per-capita average.

Frequently asked questions

That average typically includes indirect emissions from goods, services, and infrastructure that this tool's 4-category scope doesn't estimate.