Rex says
Everyday utility math — the kind you'd otherwise pull up four browser tabs for. I keep it to one clean answer.
Try a scenario
Click to load — tweak from there.Inputs
Result
Total CO2 emissions (kg)
95.2
Fuel/electricity used (gal or kWh)
10.71
CO2 per mile (kg)
0.317
Total (metric tonnes)
0.095
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter fuel type.
- 2Enter trip distance (miles).
- 3Enter fuel economy (mpg or mi/kwh).
- 4Enter grid carbon intensity (ev only) (kg CO2/kWh).
- 5Read your total co2 emissions (kg) on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Every gallon of gasoline burned releases about 8.887 kg of CO2, and diesel releases slightly more at 10.18 kg per gallon due to its higher carbon density, regardless of engine efficiency — efficiency only changes how many gallons you burn to cover a given distance. This calculator converts your trip distance and fuel economy into gallons consumed, then applies EPA emission factors to get total CO2. For electric vehicles it instead uses your electricity consumption rate and local grid carbon intensity, which varies enormously by region — a Prius on a coal-heavy grid can emit comparably to an EV on that same grid, which is why 'EVs are zero-emission' is only true at the tailpipe, not the power plant.
Worked example
Using the values the calculator loads with:
Inputs
- Fuel type: Gasoline
- Trip distance: 300 miles
- Fuel economy (MPG or mi/kWh): 28
- Grid carbon intensity (EV only): 0.37 kg CO2/kWh
Results
- Total CO2 emissions (kg): 95.2
- Fuel/electricity used (gal or kWh): 10.71
- CO2 per mile (kg): 0.317
- Total (metric tonnes): 0.095
What each field means
Inputs
- Fuel type
- Pick the option that matches your situation — the maths changes per option. Choices: Gasoline, Diesel, Electric.
- Trip distance (miles)
- The trip distance used in the calculation, measured in miles. Starts at 300 miles so you have a working example on load.
- Fuel economy (MPG or mi/kWh)
- The fuel economy (mpg or mi/kwh) used in the calculation. Starts at 28 so you have a working example on load.
- Grid carbon intensity (EV only) (kg CO2/kWh)
- The grid carbon intensity (ev only) used in the calculation, measured in kg CO2/kWh. Starts at 0.37 kg CO2/kWh so you have a working example on load. Accepted range: 0–1 kg CO2/kWh.
Results
- Total CO2 emissions (kg)
- Returned as a whole number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Fuel/electricity used (gal or kWh)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- CO2 per mile (kg)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Total (metric tonnes)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Why does diesel emit more CO2 per gallon than gasoline if it's more efficient?
Diesel is denser and contains more carbon atoms per gallon than gasoline, so it emits more CO2 per gallon burned. Diesel engines are typically 20-30% more fuel-efficient though, so the total trip emissions often still come out lower or comparable overall.
How do I find my region's grid carbon intensity for the EV calculation?
The EPA's eGRID data and the EIA publish average CO2 intensity by region and utility; it ranges from under 0.1 kg CO2/kWh in hydro-and-nuclear-heavy grids like the Pacific Northwest to over 0.7 kg CO2/kWh in coal-dependent grids, roughly a 7x spread.
Is an EV always lower-carbon than a gas car?
In almost every US grid region, yes, over the vehicle's driving lifetime, even accounting for battery manufacturing emissions, but the margin varies a lot — an EV on a very clean grid can be 3-5x lower carbon per mile than gas, while on a coal-heavy grid the advantage shrinks closer to 1.5-2x.
Does this account for manufacturing emissions?
No, this calculator is use-phase only (fuel burned or electricity consumed for driving). EVs have higher upfront manufacturing emissions from battery production, which studies show is typically offset within 1-2 years of average driving compared to a similar gas vehicle.
Accuracy and limitations
- Estimates assume standard, average conditions — local rules, pricing, and materials vary.
- Results are rounded for readability; add a buffer before ordering, booking, or committing.
- Double-check anything with a real cost attached against a local quote.
Related tools
Flight Carbon Footprint Calculator
Estimate CO2 emissions per passenger for a flight by distance and cabin class.
Home Carbon Footprint Calculator
Estimate annual household CO2 emissions from electricity, natural gas, and heating fuel use.
Tree Carbon Offset Calculator
Estimate how many trees and years are needed to offset a given amount of CO2.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Driving Carbon Footprint Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/carbon-footprint-drive
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/carbon-footprint-drive" target="_blank" rel="noopener">Driving Carbon Footprint Calculator — RevenueLab</a> (2026).</p>
Source: [Driving Carbon Footprint Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/carbon-footprint-drive) (2026).