Fuel is a variable expense
It responds quickly to route changes, traffic, and driver behavior.
Operations
Fuel Cost Calculator
Calculate trip gas cost from distance, MPG or L/100km, and fuel price. Use it for one-way drives, round trips, passenger splits, monthly commutes, and route comparisons.
Trip inputs
Enter one-way distance. Choose round trip below if needed.
Use your dashboard average, EPA rating, or real-world estimate.
Enter the pump price or local fuel-price estimate.
Use 1 for a single trip, or repeated trips for a commute/month.
Treat the number of trips as monthly trips or commute days.
Fuel cost: —
Compare another route, vehicle, or fuel price
Scenario B uses the same units, trip type, trip count, and passenger count as the main calculation.
Results
Total fuel cost
—
Fuel used:—
Cost per mile:—
Cost per km:—
Cost per passenger:—
Round-trip total:—
Monthly/repeated total:—
Comparison:—
Enter distance, efficiency, and fuel price to see the equation.
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How to choose inputs
Use map directions, odometer readings, dispatch software, or route-planning tools for distance. For MPG or fuel economy, use your dashboard average, a recent fuel log, or the vehicle rating from FuelEconomy.gov. For fuel price, enter the current pump price from a local station or fuel-price source; this page does not fetch live gas prices.
Use the U.S. preset for miles, MPG, and price per gallon. Use the metric preset for kilometers, L/100km, and price per liter. For best comparisons, change only one variable at a time, such as the route distance, vehicle efficiency, or fuel price.
Methodology and assumptions
Last updated: June 29, 2026. Author: Starlight Tools editorial team. Reviewer: Starlight Robotics calculators review.
The calculator converts the trip distance and fuel economy into fuel volume, converts that volume to the selected price unit, then multiplies by fuel price. All math runs in the browser, and inputs are not sent to a server.
- Fuel price is entered manually and may not match live station prices.
- Real-world MPG varies with terrain, speed, traffic, weather, load, tire pressure, and idling.
- Outputs exclude tolls, parking, maintenance, depreciation, charging, and non-fuel trip costs.
- Conversion constants use 1 mile = 1.609344 km, 1 U.S. gallon = 3.785411784 liters, and 1 imperial gallon = 4.54609 liters.
Fuel cost formulas
MPG: fuel gallons = miles / MPG
L/100km: fuel liters = (kilometers / 100) * L/100km
km/L: fuel liters = kilometers / km/L
Liters per mile: fuel liters = miles * liters per mile
Gallons per 100 miles: fuel gallons = (miles / 100) * gallons per 100 miles
Total fuel cost: fuel used in the price unit * fuel price
Cost per mile: total fuel cost / miles. Cost per passenger: total fuel cost / passengers.
Example: 100 miles / 25 MPG = 4 U.S. gallons, and 4 * $3.50 = $14.00.
Metric example: 160 km at 7 L/100km = 11.2 liters, and 11.2 * $1.75 = $19.60.
Unit conventions such as MPG, L/100km, and km/L are commonly used in different regions; see fuel economy unit background.
Fuel cost planning for trips and routes
For a personal trip, the main question is usually simple: how much will gas cost? Enter one-way distance, fuel economy, and fuel price, then choose round trip if you will return over the same distance. Add passengers to split the fuel cost, or add repeated trips for weekly and monthly commute estimates.
For route planning, logistics, and fleet work, the same calculation creates a consistent fuel-cost baseline. You can compare two routes, vehicles, or fuel prices in the comparison section while keeping every other assumption the same.
The results include total fuel cost, fuel needed, cost per mile, cost per kilometer, cost per passenger, round-trip total, and monthly or repeated-trip totals. Cost per mile is useful when fuel prices change, because it shows the fuel-only cost rate for each mile driven.
The calculator supports MPG using U.S. or imperial gallons, L/100km, km/L, liters per mile, and U.S. gallons per 100 miles. It also supports fuel price per U.S. gallon, imperial gallon, or liter.
FAQs
How do I calculate fuel cost?
Divide distance by fuel economy to get fuel used, then multiply by fuel price. For 100 miles at 25 MPG and $3.50 per gallon, fuel used is 4 gallons and fuel cost is $14.00.
How do I calculate fuel cost per mile?
Divide total fuel cost by miles driven. A $14.00 fuel cost over 100 miles is $0.14 per mile.
How much gas will I use for 100 miles?
At 25 MPG, 100 miles uses 4 U.S. gallons. Use distance divided by MPG, or use the calculator for other efficiency units.
How do I calculate monthly fuel cost?
Enter the one-way distance, choose round trip if needed, enter the number of trips or commute days, and turn on monthly commute mode. The calculator multiplies the trip fuel cost by that count.
Does this include tolls, parking, idling, or traffic?
No. This calculator estimates fuel cost from distance, efficiency, and fuel price only. Add tolls, parking, idling, traffic delays, or auxiliary fuel use separately.
What is the difference between MPG and L/100km?
MPG measures distance per fuel unit, so higher is better. L/100km measures fuel used per 100 kilometers, so lower is better.
Can I split fuel cost between passengers?
Yes. Enter the number of passengers and the calculator divides the total fuel cost by that number.
Is this calculator private?
Yes. All calculations run locally in your browser.
5 Fun Facts about Fuel Cost
Efficiency units differ by region
North America favors mpg, while most other regions use L/100km.
Global
Idling can add cost quickly
Long idle times can increase fuel spend without adding miles.
Idle time
Speed affects efficiency
High-speed driving often reduces mpg and increases cost per mile.
Driving
Weight impacts fuel burn
Heavier loads reduce efficiency, which can change route profitability.
Load
Disclaimer
Fuel cost estimates exclude tolls, parking, maintenance, depreciation, idling, auxiliary power usage, and traffic delays. Actual results depend on driving conditions, vehicle maintenance, terrain, load, weather, and fuel-price changes.