Fuel Consumption Calculator — Free Online Fuel Efficiency Analyzer

How to Use the Fuel Consumption Calculator

1. Enter the distance driven: Type the distance you covered between two full fill-ups. For accurate results, use the full-tank-to-full-tank method: fill your tank completely, note the odometer or reset the trip counter, drive normally, and record the distance when you fill up again. Select miles or kilometers using the distance unit dropdown.
2. Enter the fuel used: Input the amount of fuel consumed for that distance, which is the number of gallons or liters you pumped at the second fill-up. Select the appropriate unit from the fuel unit dropdown. Using a complete fill-up ensures the fuel measurement corresponds exactly to the distance driven.
3. Enter the fuel price: Type the price per gallon or per liter that you paid. This value is used to calculate your cost-per-mile figures and to project annual and monthly fuel expenses. If prices vary, use the average price you typically pay.
4. Enter your annual driving distance: Input your estimated total annual driving distance in the same units (miles or kilometers) as your distance measurement. The average American drives approximately 12,000 to 15,000 miles per year. This allows the calculator to project your total annual fuel expense, monthly cost, and yearly CO2 emissions.

Results update in real time and display your fuel efficiency in three international formats (MPG, L/100km, km/L), projected annual and monthly costs, and estimated annual CO2 emissions in pounds. Switch between US and metric units using the dropdown selectors.

Fuel Consumption Formula

Variables Explained

• MPG (Miles Per Gallon): The US standard for fuel economy, measuring distance traveled per unit of fuel. Higher is better. Used universally in the United States for vehicle specifications, EPA ratings, and consumer comparisons.
• L/100km (Liters Per 100 Kilometers): The European and international standard for fuel consumption. Unlike MPG, lower values indicate better efficiency. This metric scales linearly with fuel cost, making it mathematically superior for comparing vehicles and calculating expenses.
• km/L (Kilometers Per Liter): Used in parts of Asia and South America. Like MPG, higher values indicate better efficiency. It represents how far you travel on one liter of fuel.
• Annual Fuel Cost: The projected yearly expense for fuel based on your driving distance and fuel economy. This is calculated by determining annual gallons consumed (annual miles divided by MPG) and multiplying by the fuel price.
• CO2 Emissions: Each gallon of gasoline produces approximately 19.6 pounds of carbon dioxide when burned. Annual emissions are calculated by multiplying total annual gallons consumed by this factor, giving you a measure of your driving's environmental impact.

Step-by-Step Example

Suppose you drove 320 miles on 11.5 gallons of gas at $3.55 per gallon, and you drive approximately 14,000 miles per year:

1. Calculate MPG: 320 / 11.5 = 27.8 MPG
2. Convert to L/100km: 235.215 / 27.8 = 8.5 L/100km
3. Convert to km/L: 27.8 x 0.425 = 11.8 km/L
4. Calculate annual gallons: 14,000 / 27.8 = 503.6 gallons
5. Calculate annual fuel cost: 503.6 x $3.55 = $1,787.78
6. Calculate monthly fuel cost: $1,787.78 / 12 = $148.98
7. Calculate annual CO2: 503.6 x 19.6 = 9,871 lbs

Your vehicle runs at 27.8 MPG (8.5 L/100km), costing approximately $1,788 per year in fuel and producing nearly 9,871 pounds (4.48 metric tons) of CO2 annually. This data helps you compare the cost and environmental impact of your current vehicle against alternatives.

Practical Examples

Example 1: James Compares Two Cars He's Considering

James is deciding between a compact sedan and a midsize SUV. He drives about 15,000 miles per year and gas costs $3.50 per gallon in his area. He uses fuel consumption data from test drives to compare:

• Sedan: 340 miles on 10.3 gallons = 33.0 MPG (7.1 L/100km)
• SUV: 280 miles on 12.7 gallons = 22.0 MPG (10.7 L/100km)
• Sedan annual cost: (15,000 / 33.0) x $3.50 = $1,590.91
• SUV annual cost: (15,000 / 22.0) x $3.50 = $2,386.36
• Annual difference: $2,386.36 - $1,590.91 = $795.45
• Sedan CO2: 454.5 gal x 19.6 = 8,909 lbs
• SUV CO2: 681.8 gal x 19.6 = 13,363 lbs

The sedan saves James $795 per year in fuel and produces 4,454 fewer pounds of CO2 annually. Over a 5-year ownership period, the sedan saves $3,977 in fuel alone, which James factors into his total cost-of-ownership comparison between the two vehicles.

Example 2: Sophie Tracks Her Driving in Europe

Sophie lives in Germany and tracks her fuel consumption in metric units. She drove 450 km on 38 liters of diesel at 1.65 euros per liter, and drives approximately 18,000 km per year:

• L/100km: (38 / 450) x 100 = 8.4 L/100km
• km/L: 450 / 38 = 11.8 km/L
• MPG equivalent: 235.215 / 8.4 = 28.0 MPG
• Annual liters: (18,000 / 100) x 8.4 = 1,512 liters
• Annual cost: 1,512 x 1.65 = 2,494.80 euros

Sophie's diesel sedan consumes 8.4 L/100km, which translates to about 28 MPG in US terms. Her annual fuel cost is approximately 2,495 euros. She uses this baseline to evaluate whether switching to a hybrid or electric vehicle would be cost-effective given the higher electricity rates in Europe.

Example 3: Mike Evaluates His Truck's Work Efficiency

Mike runs a delivery business using a large cargo van. He tracked 180 miles over 14.5 gallons at $3.60 per gallon. The van drives 35,000 miles per year for deliveries:

• MPG: 180 / 14.5 = 12.4 MPG
• L/100km: 235.215 / 12.4 = 19.0 L/100km
• Annual gallons: 35,000 / 12.4 = 2,822.6 gallons
• Annual fuel cost: 2,822.6 x $3.60 = $10,161.29
• Monthly fuel cost: $10,161.29 / 12 = $846.77
• Annual CO2: 2,822.6 x 19.6 = 55,323 lbs (25.1 metric tons)

Mike's delivery van costs over $10,000 per year in fuel. This data motivates him to optimize delivery routes, consider a more fuel-efficient vehicle, or explore an electric cargo van that could reduce his fuel costs by 60% or more. Even a 2 MPG improvement would save him approximately $1,400 annually.

Fuel Consumption Reference Table

Annual cost assumes 12,000 miles per year at $3.50/gallon. CO2 calculated at 19.6 lbs per gallon of gasoline.

Tips and Complete Guide

Understanding the True Cost of Fuel Consumption

Fuel is typically the second largest expense of vehicle ownership after depreciation, accounting for 15% to 25% of total cost. For the average American driving 12,000 miles per year, annual fuel costs range from $840 for a 50 MPG hybrid to $2,800 for a 15 MPG truck. Over a typical 5-year ownership period, the difference between a 25 MPG and 35 MPG vehicle is approximately $2,400. When shopping for a new vehicle, factor in projected fuel costs over your expected ownership period to get a complete picture of what each option truly costs. A more expensive but fuel-efficient vehicle may have a lower total cost of ownership than a cheaper but fuel-hungry alternative.

The MPG Illusion and Why L/100km Matters

One of the most important insights in fuel consumption is the MPG illusion, first described by researchers at Duke University. Because MPG has a non-linear relationship with fuel consumed, improvements at low MPG values save far more fuel than the same improvement at high MPG values. Replacing a 10 MPG vehicle with a 20 MPG vehicle saves 600 gallons over 12,000 miles. But replacing a 25 MPG vehicle with a 50 MPG vehicle saves only 240 gallons over the same distance. This means swapping a gas-guzzling truck for a moderately efficient one saves more fuel than swapping a decent sedan for a hybrid. The L/100km metric avoids this illusion entirely because it scales linearly: going from 15 L/100km to 10 L/100km always saves the same amount of fuel as going from 10 to 5 L/100km over the same distance.

Reducing Your Carbon Footprint Through Driving

Transportation accounts for roughly 29% of greenhouse gas emissions in the United States, with personal vehicles being a major contributor. Each gallon of gasoline burned produces 19.6 pounds of CO2, while each gallon of diesel produces 22.4 pounds. The most effective ways to reduce your driving carbon footprint are reducing total miles driven through carpooling, public transit, and trip consolidation; maintaining efficient driving habits that maximize your MPG; keeping your vehicle well maintained; and ultimately transitioning to an electric or hybrid vehicle. Even improving from 20 MPG to 25 MPG reduces annual CO2 by 2,352 pounds, which is equivalent to planting roughly 29 trees. Check our EV charging calculator to compare the environmental impact of switching to electric.

Common Mistakes to Avoid

• Falling for the MPG illusion: Do not assume that a 10 MPG improvement saves the same amount of fuel regardless of the starting point. Going from 15 to 25 MPG saves dramatically more fuel and money than going from 30 to 40 MPG over the same driving distance.
• Not using the full-tank method: Estimating fuel used without filling to the same level each time introduces significant errors. Always measure from full to full for reliable consumption data.
• Comparing different driving conditions: Fuel consumption measured on a long highway trip cannot be fairly compared to a week of city driving. Track consumption over similar driving patterns for meaningful comparisons over time.
• Ignoring the annual cost perspective: A small daily savings in fuel consumption adds up to hundreds or thousands of dollars per year. Always calculate the annual impact to appreciate the true financial significance of fuel efficiency differences.
• Forgetting that units change the math: When switching between metric and imperial units, ensure consistency. Mixing liters of fuel with miles of distance or gallons with kilometers produces meaningless results. Our calculator handles unit conversions automatically to prevent this error.

Frequently Asked Questions