Fuel Cost Calculator
Estimate trip fuel expenses by distance and efficiency.
Fuel Cost Results
What is a Fuel Cost Calculator?
A fuel cost calculator estimates how much you will spend on gasoline or diesel for a trip before you leave the driveway. Enter the trip distance, your vehicle's fuel efficiency, and the local fuel price, and the tool returns how much fuel you will burn, the total cost, and the cost per mile or kilometer.
Fuel is one of the largest variable costs of driving, and small differences in efficiency or pump price add up over thousands of miles. Knowing the cost in advance helps you budget a road trip, compare vehicles, decide whether a detour is worth it, or weigh a commute against public transit.
The calculator supports both major efficiency systems: MPG (miles per gallon), common in the United States, and L/100km (liters per 100 kilometers), used in most other countries.
The Fuel Cost Formula
The math divides your distance by how efficiently the car uses fuel, then multiplies by the price per unit:
Fuel Used (gallons) = Trip Distance (miles) ÷ Fuel Efficiency (MPG)
Fuel Used (liters) = Trip Distance (km) × (Efficiency (L/100km) ÷ 100)
Total Fuel Cost = Fuel Used × Price per Gallon (or per Liter)
Cost per Mile (or km) = Total Fuel Cost ÷ Trip Distance
- Trip Distance — the total length of the trip in miles (MPG mode) or kilometers (L/100km mode). For a round trip, double the one-way distance.
- Fuel Efficiency — your vehicle's consumption rating. With MPG, higher is cheaper; with L/100km, lower is cheaper. Use your real-world average, not the window-sticker figure, for the most accurate estimate.
- Fuel Price — the price at the pump per gallon or per liter, depending on the mode.
Results also show the "other" unit cost: in MPG mode the tool converts miles to kilometers (1 mile = 1.609344 km) and reports cost per kilometer; in L/100km mode it reports cost per mile.
Worked Example: A 285-Mile Trip at 32 MPG
Imagine a 285-mile weekend trip in a car that averages 32 MPG, with gas priced at $3.65 per gallon:
- Fuel needed: 285 ÷ 32 = 8.90625 gallons, which displays as 8.91 gallons.
- Total cost: 8.90625 × $3.65 = $32.5078, which rounds to $32.51.
- Cost per mile: $32.5078 ÷ 285 = $0.1141, shown as $0.11.
- Cost per kilometer: 285 miles × 1.609344 = 458.66 km, so $32.5078 ÷ 458.66 = $0.0709, shown as $0.07.
Drive back and the 570-mile round trip burns 570 ÷ 32 = 17.8125 gallons and costs 17.8125 × $3.65 = $65.0156, or about $65.02.
Metric mode works the same way: a 480 km trip at 7.5 L/100km with fuel at $1.45 per liter uses 480 × (7.5 ÷ 100) = 36 liters, costing 36 × $1.45 = $52.20. Since 480 km ÷ 1.609344 = 298.26 miles, that is $0.10875 per km or $0.18 per mile.
Fuel Cost for Common Trips
This table assumes gas at $3.50 per gallon and shows the fuel used, with the total cost in parentheses, for three typical efficiency ratings.
| Trip Distance | 20 MPG | 30 MPG | 40 MPG |
|---|---|---|---|
| 100 miles | 5.00 gal ($17.50) | 3.33 gal ($11.67) | 2.50 gal ($8.75) |
| 300 miles | 15.00 gal ($52.50) | 10.00 gal ($35.00) | 7.50 gal ($26.25) |
| 500 miles | 25.00 gal ($87.50) | 16.67 gal ($58.33) | 12.50 gal ($43.75) |
Estimating Annual Fuel Spend
The same formula scales to annual budgeting: 12,000 miles a year at 28 MPG with $3.50 gas burns 12,000 ÷ 28 = 428.57 gallons and costs exactly $1,500. A 35 MPG car burns 342.86 gallons and costs $1,200 — a $300 yearly saving.
How to Use
- Select your Efficiency Mode: MPG (miles per gallon) or L/100km (liters per 100 km). The field labels switch units automatically.
- Enter the Trip Distance in miles or kilometers, matching the mode.
- Enter your vehicle's Fuel Efficiency rating.
- Enter the Fuel Price per gallon or per liter at your local station.
- Click Calculate Cost to see the total fuel needed, the total cost, and the cost per mile and per kilometer.
Frequently Asked Questions
What is the difference between MPG and L/100km?
MPG measures how many miles a car travels on one gallon, so a higher number is better. L/100km measures how many liters the car burns over 100 kilometers, so a lower number is better. The two are inverses: L/100km = 235.215 ÷ MPG, so 30 MPG equals about 7.84 L/100km, while 6 L/100km equals about 39.2 MPG.
Can I use this for multiple stops?
Yes. Fuel use scales linearly with distance, so add up every leg and enter it as one trip. A 120-mile leg plus an 80-mile leg burns the same fuel as a single 200-mile trip — 6.25 gallons at 32 MPG in both cases.
How do I find my car's actual MPG?
Fill the tank, reset the trip odometer, drive normally, and at the next fill-up divide the miles driven by the gallons added. Driving 320 miles on 10.7 gallons gives 320 ÷ 10.7 = 29.9 MPG. Average a few tanks for a reliable figure, since window-sticker ratings often run higher than real-world results.
Why is my actual fuel cost higher than the estimate?
The calculator assumes steady efficiency, but cold starts, stop-and-go traffic, high speeds, air conditioning, and heavy loads all raise consumption. A car rated at 32 MPG that manages only 28 MPG in winter turns the 285-mile example into 285 ÷ 28 = 10.18 gallons, or $37.15 instead of $32.51.
Does the calculator include tolls, parking, or wear and tear?
No. It estimates fuel expense only. Tolls, parking, maintenance, depreciation, and insurance are separate costs, so add those to the fuel figure if you need the full price of driving somewhere.
Does it work for electric vehicles?
No, this tool estimates liquid fuel costs for gasoline or diesel vehicles. EVs consume kilowatt-hours rather than gallons or liters, and charging prices vary by network and time of day, so use an EV charging cost calculator for electric vehicles.