Fuel Cost Calculator — Trip, Monthly and Vehicle Comparison
Our free fuel cost calculator helps you estimate gas costs for any trip, calculate your monthly and annual fuel spend, and compare the running costs of two vehicles side by side — including electric vehicles. Enter your distance, fuel efficiency, and price per gallon or liter for instant results.
How to Calculate Fuel Cost
The basic formula for calculating fuel cost is:
Fuel Cost = (Distance ÷ MPG) × Price per Gallon
Or in metric:
Fuel Cost = (Distance × L/100km ÷ 100) × Price per Liter
| Trip Distance | MPG | Price/Gallon | Gallons Used | Total Cost |
|---|---|---|---|---|
| 100 miles | 25 MPG | $3.50 | 4.0 gal | $14.00 |
| 100 miles | 30 MPG | $3.50 | 3.3 gal | $11.67 |
| 100 miles | 40 MPG | $3.50 | 2.5 gal | $8.75 |
| 500 miles | 25 MPG | $3.50 | 20.0 gal | $70.00 |
| 500 miles | 30 MPG | $3.50 | 16.7 gal | $58.33 |
| 500 miles | 30 MPG | $4.00 | 16.7 gal | $66.67 |
Annual Fuel Cost by MPG and Mileage
Based on 15,000 miles driven per year at $3.50/gallon:
| Fuel Efficiency | Annual Gallons | Annual Fuel Cost | Monthly Cost |
|---|---|---|---|
| 15 MPG (old truck) | 1,000 gal | $3,500 | $292 |
| 20 MPG (SUV) | 750 gal | $2,625 | $219 |
| 25 MPG (sedan) | 600 gal | $2,100 | $175 |
| 30 MPG (efficient) | 500 gal | $1,750 | $146 |
| 35 MPG (hybrid) | 429 gal | $1,500 | $125 |
| 45 MPG (Prius-like) | 333 gal | $1,167 | $97 |
| 50 MPG (top hybrid) | 300 gal | $1,050 | $88 |
MPG to L/100km Conversion Table
| MPG (US) | L/100km | km/L | Description |
|---|---|---|---|
| 10 | 23.5 | 4.3 | Very inefficient (large truck) |
| 15 | 15.7 | 6.4 | Inefficient (old SUV) |
| 20 | 11.8 | 8.5 | Below average (truck/large SUV) |
| 25 | 9.4 | 10.6 | Average (mid-size SUV) |
| 30 | 7.8 | 12.7 | Good (sedan) |
| 35 | 6.7 | 14.9 | Very good (small car) |
| 40 | 5.9 | 17.0 | Excellent (compact/mild hybrid) |
| 45 | 5.2 | 19.1 | Outstanding (full hybrid) |
| 50 | 4.7 | 21.3 | Top hybrid range |
| 55 | 4.3 | 23.4 | Best non-EV vehicles |
| 120 | 2.0 | 50.0 | Typical EV (MPGe equivalent) |
Gas vs Electric Vehicle Cost Comparison
Electric vehicles have higher purchase prices but lower fuel costs. Here is a typical comparison:
| Metric | Gas Car (30 MPG) | Electric Vehicle | EV Advantage |
|---|---|---|---|
| Fuel/Energy efficiency | 30 MPG | 3.5 mi/kWh (equiv ~119 MPGe) | ~4× more efficient |
| Fuel cost per mile | ~$0.12/mi | ~$0.05/mi (at $0.16/kWh) | Save ~$0.07/mi |
| Annual fuel cost | ~$1,750 | ~$700 (15k miles) | Save ~$1,050/year |
| 10-year fuel cost | ~$17,500 | ~$7,000 | Save ~$10,500 |
| CO₂ per mile | ~300g | ~110g (US grid avg) | 63% less CO₂ |
At $3.50/gal gas, $0.16/kWh electricity, 15,000 miles/year.
Factors That Affect Real-World Fuel Economy
Your actual MPG may differ significantly from the EPA estimate on the window sticker:
- Speed — Fuel efficiency drops sharply above 55 mph. Highway driving at 70 mph can reduce MPG by 10-15% compared to 55 mph.
- Acceleration and braking — Aggressive driving reduces fuel economy by 15-30% in city driving and 10-40% on highways.
- Tire pressure — Under-inflated tires increase rolling resistance. Each 10 psi below optimal reduces MPG by 0.2%.
- Air conditioning — AC reduces MPG by 5-25% depending on conditions. At highway speeds, opening windows causes more drag than AC.
- Cold weather — Cold temperatures reduce MPG by 15-24% in city driving as the engine takes longer to reach optimal temperature.
- Cargo and roof racks — Extra weight (100 lbs) reduces MPG by about 1%. Roof cargo increases drag and reduces highway MPG by 10-25%.
- Fuel grade — Using premium fuel in a car that does not require it provides no benefit. Using regular in a car requiring premium reduces performance and efficiency.
Reducing Your Fuel Costs
| Strategy | Typical Fuel Savings | Difficulty |
|---|---|---|
| Maintain proper tire pressure | 0.5-3% | Very Easy |
| Remove unnecessary cargo | 1-2% | Easy |
| Use cruise control on highways | 7-14% | Easy |
| Reduce highway speed (70→60 mph) | 10-15% | Moderate |
| Smooth acceleration/braking | 15-30% | Moderate |
| Shop around for cheapest local gas | Varies | Easy |
| Get regular tune-ups | 4-40% | Easy (pay mechanic) |
| Use recommended motor oil | 1-2% | Easy |
| Park in shade (reduces AC load) | 1-5% | Easy |
| Plan routes to avoid congestion | Variable | Moderate |
Frequently Asked Questions
How much does it cost to drive 100 miles in gas?
At 30 MPG and $3.50/gallon, 100 miles costs $11.67 (100 ÷ 30 × $3.50). At 25 MPG, it costs $14.00. At 20 MPG, it costs $17.50. Enter your actual vehicle efficiency and local gas price in the calculator for a precise answer.
How do I find my car's MPG?
The easiest method: fill your tank completely, reset your trip odometer to zero, drive normally, then fill up again. Divide the miles driven by the gallons it took to fill up. Alternatively, check the EPA fuel economy label at fueleconomy.gov for your vehicle's rated MPG. Real-world MPG typically runs 5-15% below the EPA estimate.
How much does gas cost per month for the average American?
The average American drives approximately 1,200-1,300 miles per month. At 25 MPG and $3.50/gallon, that is approximately $168-$182 per month in gas. This varies widely by location, vehicle, and driving patterns.
Is it worth getting a more fuel-efficient car?
Switching from 20 MPG to 30 MPG saves approximately $875/year at $3.50/gallon and 15,000 miles driven. Over 5 years that is $4,375 in fuel savings. Whether that justifies the vehicle cost difference depends on the price gap between vehicles. Use the Vehicle Comparison mode to calculate the break-even point for your specific situation.
How do I calculate cost per mile for my vehicle?
Divide your fuel price by your MPG to get fuel cost per mile. At $3.50/gallon and 30 MPG: $3.50 ÷ 30 = $0.117 per mile. Note this is fuel cost only — total cost per mile including depreciation, insurance, and maintenance is typically $0.45-$0.65 per mile for the average American vehicle according to AAA data.