# Driving Carbon Footprint Calculator

> Estimates tailpipe CO₂ (and CO₂-equivalent including methane and nitrous oxide) for a car trip from distance and fuel economy or fuel used, using per-litre combustion factors for petrol, diesel and LPG, and scales to a yearly total.

- Calculator id: `carbon-footprint-driving` · Category: Weather & Environment (`weather`) · Tool name: `estimate_driving_carbon_footprint`
- Canonical page: https://tttkmbb.com/weather/carbon-footprint-driving · This document: https://tttkmbb.com/weather/carbon-footprint-driving.md · JSON definition: https://tttkmbb.com/weather/carbon-footprint-driving.json

## Purpose

Estimates tailpipe CO₂ (and CO₂-equivalent including methane and nitrous oxide) for a car trip from distance and fuel economy or fuel used, using per-litre combustion factors for petrol, diesel and LPG, and scales to a yearly total.

**Use when:** You want the CO₂ emissions of a commute, road trip or annual mileage for a petrol, diesel or LPG vehicle, in kilograms and grams per kilometre.

**Do not use when:** The vehicle is electric or plug-in hybrid (use carbon-footprint-electricity with the kWh consumed), you need lifecycle/well-to-wheel emissions, or you only need the fuel cost (use fuel-cost).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `distance` | number |  | required | Distance of one trip in distance_unit. (> 0, max 1000000) |
| `distance_unit` | enum: km \| mi |  | optional, default "km" | Unit of the distance. |
| `fuel_economy` | number |  | optional | Vehicle fuel economy in fuel_economy_unit. Not needed when fuel_used_liters is given. (> 0, max 1000) |
| `fuel_economy_unit` | enum: l_per_100km \| mpg_us \| mpg_uk \| km_per_l |  | optional, default "l_per_100km" | Unit of fuel_economy. |
| `fuel_used_liters` | number | L | optional | Litres of fuel burned on the trip, if known; overrides fuel_economy. (> 0, max 100000) |
| `fuel_type` | enum: petrol \| diesel \| lpg |  | optional, default "petrol" | Fuel burned; selects the kg CO₂ per litre combustion factor. |
| `trips_per_year` | number |  | optional, default 1 | How many times the trip is driven per year (e.g. 230 for a one-way daily commute, 460 for both directions). (min 1, max 100000) |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `fuel_liters` | number | L | Litres of fuel burned on one trip. |
| `co2_kg_per_trip` | number | kg | Tailpipe carbon dioxide from combustion, fuel_liters × factor. |
| `co2e_kg_per_trip` | number | kg | Tailpipe greenhouse gases including CH₄ and N₂O, CO₂ ÷ 0.994 (EPA 2022 ratio for passenger vehicles). |
| `co2_g_per_km` | number | g/km | Grams of CO₂ per kilometre driven. |
| `co2_kg_per_year` | number | kg | co2_kg_per_trip × trips_per_year. |
| `co2e_kg_per_year` | number | kg | co2e_kg_per_trip × trips_per_year. |
| `emission_factor_kg_per_liter` | number | kg CO₂/L | Combustion factor applied for the selected fuel. |
| `distance_km` | number | km | Trip distance in kilometres. |

## Formula

`fuel_L = distance_km × L/100km ÷ 100 (mpg converted via 235.215/mpg_US or 282.481/mpg_UK; km/L via 100/(km/L)); CO₂ = fuel_L × factor (petrol 2.31, diesel 2.68, LPG 1.51 kg/L); CO₂e = CO₂ / 0.994; per year = per trip × trips_per_year`

Tank-to-wheel combustion factors as of 2024: they match the UK DEFRA/DESNZ 2024 factors for 100 % mineral petrol and diesel and the US EPA values (8,887 g CO₂ per US gallon of petrol = 2.35 kg/L, 10,180 g/gal diesel = 2.69 kg/L) within 2 %. Upstream (well-to-tank) emissions add roughly 20 % and are not included.

## Data Sources

- US EPA – Greenhouse Gas Emissions from a Typical Passenger Vehicle (8,887 g CO₂/gal petrol, 10,180 g CO₂/gal diesel) — https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-typical-passenger-vehicle (government, retrieved 2026-09-24)
- UK DESNZ/DEFRA – Greenhouse gas reporting: conversion factors 2024 (fuels per litre, electricity) — https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2024 (government, retrieved 2026-09-24)
- US EPA – Greenhouse Gas Equivalencies Calculator: calculations and references (eGRID 2022 US average 823.1 lb CO₂/MWh; vehicle CO₂/GHG ratio 0.994) — https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references (government, retrieved 2026-09-24)

Data freshness: `static`. Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output.

## API

- `GET https://tttkmbb.com/api/v1/calculate/carbon-footprint-driving?distance=…`
- `POST https://tttkmbb.com/api/v1/calculate/carbon-footprint-driving` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/carbon-footprint-driving · OpenAPI operationId `estimate_driving_carbon_footprint` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "carbon-footprint-driving", "inputs": {…}}`

## Example

- 100 km at 7 L/100 km, petrol, 230 trips/year: inputs `{"distance":100,"distance_unit":"km","fuel_economy":7,"fuel_economy_unit":"l_per_100km","fuel_type":"petrol","trips_per_year":230}` → `{"fuel_liters":7,"co2_kg_per_trip":16.17,"co2e_kg_per_trip":16.27,"co2_g_per_km":161.7,"co2_kg_per_year":3719.1,"emission_factor_kg_per_liter":2.31}`
- 30 miles at 30 mpg (US), diesel: inputs `{"distance":30,"distance_unit":"mi","fuel_economy":30,"fuel_economy_unit":"mpg_us","fuel_type":"diesel"}` → `{"distance_km":48.28,"fuel_liters":3.79,"co2_kg_per_trip":10.14,"co2_g_per_km":210.1}`

```
GET https://tttkmbb.com/api/v1/calculate/carbon-footprint-driving?distance=100&distance_unit=km&fuel_economy=7&fuel_economy_unit=l_per_100km&fuel_type=petrol&trips_per_year=230
```

## Limitations

The vehicle is electric or plug-in hybrid (use carbon-footprint-electricity with the kWh consumed), you need lifecycle/well-to-wheel emissions, or you only need the fuel cost (use fuel-cost). Tank-to-wheel combustion factors as of 2024: they match the UK DEFRA/DESNZ 2024 factors for 100 % mineral petrol and diesel and the US EPA values (8,887 g CO₂ per US gallon of petrol = 2.35 kg/L, 10,180 g/gal diesel = 2.69 kg/L) within 2 %. Upstream (well-to-tank) emissions add roughly 20 % and are not included. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Why is diesel's factor higher if diesel cars emit less?**

Diesel contains more carbon per litre (2.68 vs 2.31 kg CO₂), but diesel engines use fewer litres per 100 km; compare grams per kilometre, not per litre.

**What is the difference between CO₂ and CO₂e here?**

CO₂e adds the tailpipe methane and nitrous oxide weighted by global-warming potential; for modern cars that is under 1 % (EPA ratio 0.994), so both numbers are close.

**Does this include fuel production?**

No. Well-to-tank emissions from extracting, refining and transporting the fuel add about 20 % (DEFRA well-to-tank factors); electricity and lifecycle comparisons should include them.

## Related

- [Electricity Carbon Footprint Calculator](https://tttkmbb.com/weather/carbon-footprint-electricity.md) — Emissions of electricity use, including EV charging.
- [Fuel Cost Calculator](https://tttkmbb.com/everyday/fuel-cost.md) — Cost of the same trip from fuel price and economy.
- [Fuel Economy Converter](https://tttkmbb.com/conversion/fuel-economy.md) — Convert between L/100 km, mpg and km/L.