How is the annual fuel cost saving calculated?

Annual fuel used = annual distance ÷ fuel economy (km/L) is computed for the before and after cases, and the difference in fuel cost (fuel used × price per liter) is shown as the annual saving. CO2 reduction is found the same way from the difference in fuel used.

When should I use this instead of the car CO2 tool?

This tool compares before and after fuel economy to show the money and CO2 you save. If you just want the fuel used, cost, and CO2 for a single trip or distance, use the car fuel economy and CO2 tool instead.

Which inputs make the estimate more accurate?

Use your real average fuel economy rather than catalog figures, and enter the current price from a recent fuel receipt. The CO2 factors default to about 2.32 (gasoline), 2.58 (diesel), and 2.49 (kerosene) kg-CO2/L and can be changed.

Fuel Savings Calculator

Enter your annual mileage and your fuel economy before and after to estimate how much you'll save on yearly fuel costs and how much CO2 you'll cut. See the impact of eco-driving or switching cars in real numbers.

Last updated: June 25, 2026

Input

Enter your annual driving distance and your fuel economy before and after, and we'll estimate how much you can cut from your yearly fuel cost and CO2 emissions.

Annual driving distance

Fuel economy (before)

km/L

Fuel economy (after)

km/L

Fuel price

CO2 factor (fuel type)

CO2 emission factor

kg-CO2/L

Result

Annual fuel cost savings

$48,611.11

About $4,050.93/month saved

Annual CO2 reduction

644.4 kg

Annual fuel cost (before)

$145,833.33

Annual fuel cost (after)

$97,222.22

Before vs. after comparison (annual)

Item	Before	After	Saved
Fuel used	833.3 L	555.6 L	277.8 L
Fuel cost	$145,833.33	$97,222.22	$48,611.11
CO2 emissions	1,933.3 kg	1,288.9 kg	644.4 kg

How it works

Annual fuel used is calculated as annual driving distance divided by fuel economy (km/L). The fuel saved is the difference between the before and after amounts.
Annual fuel cost is fuel used multiplied by the fuel price per liter. The difference between the before and after costs is shown as the headline "annual fuel cost savings."
CO2 emissions are fuel used multiplied by the CO2 emission factor (kg-CO2/L). Default factors are roughly 2.32 for gasoline, 2.58 for diesel, and 2.49 for kerosene; you can enter your own. These are estimates only.
Fuel prices vary widely by country, region, and over time. Enter your local pump price (for example from a recent receipt) for a more realistic estimate.
Fuel economy changes a lot with driving style, season, load, and traffic. Using your real average economy rather than catalog figures improves accuracy.
Results use representative factors and are estimates only. They do not guarantee actual fuel costs or CO2 emissions; use them as a rough guide.

Frequently asked questions

How is the annual fuel cost saving calculated?: Annual fuel used = annual distance ÷ fuel economy (km/L) is computed for the before and after cases, and the difference in fuel cost (fuel used × price per liter) is shown as the annual saving. CO2 reduction is found the same way from the difference in fuel used.
When should I use this instead of the car CO2 tool?: This tool compares before and after fuel economy to show the money and CO2 you save. If you just want the fuel used, cost, and CO2 for a single trip or distance, use the car fuel economy and CO2 tool instead.
Which inputs make the estimate more accurate?: Use your real average fuel economy rather than catalog figures, and enter the current price from a recent fuel receipt. The CO2 factors default to about 2.32 (gasoline), 2.58 (diesel), and 2.49 (kerosene) kg-CO2/L and can be changed.

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