Fuel Cost Calculator
Estimate how much gas your trip will cost using the driving distance, your vehicle's MPG, and the price of gas per gallon. Get total fuel cost, gallons needed, cost per mile, and a round-trip estimate instantly.
Fuel cost calculator
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How Much Will Gas Cost for Your Trip?
Divide the miles you will drive by your vehicle’s miles per gallon, then multiply by the price of a US gallon. A 100-mile drive in a 25 MPG car at $3.50 per gallon uses 4 gallons and costs $14.00. That is $0.14 per mile in fuel only.
Distance, fuel efficiency, and pump price are the three inputs. Everything else on this page—round trip, passengers, commute days, and a consumption buffer—is a convenience on top of that same math.
How to Use the Fuel Cost Calculator
- Enter one-way trip distance in miles or kilometers.
- Enter fuel efficiency as US MPG, km/L, or L/100km.
- Enter gas price per US gallon or per liter. Use the price you will actually pay—this field is not a live average.
- Turn on round trip only if you entered a one-way distance. Open the optional panel to split cost, estimate a commute, add a buffer, or compare a second vehicle.
Fuel Cost Calculator Formula
Gallons needed = miles ÷ US MPG
Fuel cost = gallons × price per US gallon
Cost per mile = fuel cost ÷ miles
Worked example: 400 miles ÷ 32 MPG = 12.5 gallons. At $3.60 per gallon the fuel cost is $45.00, or $0.1125 per mile before display rounding.
Liters needed (L/100km) = km × (L/100km ÷ 100)
Liters needed (km/L) = km ÷ km/L
The calculator uses a US gallon of 3.785411784 liters and a mile of 1.609344 kilometers. It does not use imperial gallons.
Fuel Cost Examples
Illustrative prices and MPG values. They are not current pump prices.
- 100-mile drive, 25 MPG, $3.50/gal: 4.00 gallons, $14.00, $0.14/mile.
- 500-mile road trip, 28 MPG, $3.45/gal: 17.86 gallons, $61.61.
- 250 miles one way, round trip on, 28 MPG, $3.45/gal: 500 miles, $61.61.
- 100 one-way miles, round trip, two paying passengers, 25 MPG, $3.50/gal: $28.00 total, $14.00 each.
- 25-mile one-way commute, 22 working days, 25 MPG, $3.50/gal: $154.00/month, $1,848.00/year.
- 500 miles at $3.50/gal: SUV ~22 MPG costs $79.55; hybrid ~45 MPG costs $38.89.
- 400 km, 8 L/100km, 1.80 per liter: 32 liters and 57.60 in the selected currency.
Fuel cost at $3.50 per gallon
| MPG | 100 mi | 250 mi | 500 mi | 1,000 mi |
|---|---|---|---|---|
| 18 | $19.44 | $48.61 | $97.22 | $194.44 |
| 22 | $15.91 | $39.77 | $79.55 | $159.09 |
| 25 | $14.00 | $35.00 | $70.00 | $140.00 |
| 30 | $11.67 | $29.17 | $58.33 | $116.67 |
| 45 | $7.78 | $19.44 | $38.89 | $77.78 |
Calculate Gas Cost for a Round Trip
If you enter a one-way distance, enable round trip to double it. A 250-mile drive each way is 500 miles of fuel. At 28 MPG and $3.45 per gallon that is $61.61—the same result as entering 500 miles with round trip off. Do not enter 500 miles and also enable round trip unless you truly intend to budget 1,000 miles.
Calculate Monthly Commuting Fuel Costs
Monthly miles = one-way miles × 2 × working days per month
A 25-mile one-way commute, 22 working days, 25 MPG, and $3.50 per gallon is 1,100 miles, 44 gallons, $154.00 per month, and $1,848.00 per year (12 × monthly). Annual uses the same working-day assumption, not a separate 260-day calendar.
How to Calculate Gas Cost per Mile
Cost per mile = (price per gallon) ÷ MPG
At $3.50 per gallon and 25 MPG, fuel costs $0.14 per mile. That is fuel only. IRS standard mileage rates, insurance, tires, and depreciation are separate from this calculator.
MPG vs. L/100km and km/L
US MPG is miles per US gallon—higher is better. km/L is kilometers per liter—higher is better. L/100km is liters used per 100 kilometers—lower is better. Switching units in the calculator preserves the physical efficiency.
L/100km = 235.215 ÷ US MPG
30 US MPG is about 7.84 L/100km. Currency selection only changes the symbol; it does not convert dollars to euros.
What Affects Fuel Costs?
- Highway speed and aggressive acceleration reduce MPG.
- Stop-and-go traffic, cold starts, and short trips use more fuel per mile.
- Low tire pressure, roof cargo, and extra passengers add load.
- Hills, headwinds, and air conditioning increase consumption.
- Local pump prices vary by station, grade, and state taxes. Enter the price you will pay.
Common Fuel Cost Calculation Mistakes
- Mixing miles with L/100km, or US gallons with imperial gallons.
- Entering a round-trip total and also turning on round trip.
- Using sticker highway MPG for a loaded city commute.
- Treating fuel cost as the full cost of driving.
Frequently Asked Questions
How do I calculate gas cost for a trip?
Divide trip miles by US MPG to get gallons, then multiply by the price per gallon. Example: 400 miles ÷ 32 MPG = 12.5 gallons × $3.60 = $45.00.
How much gas will I need for 500 miles?
Gallons = 500 ÷ MPG. At 28 MPG that is about 17.86 gallons. At $3.45 per gallon the fuel cost is $61.61. Use your own MPG and pump price.
How much does it cost to drive 100 miles?
At 25 MPG and $3.50 per gallon, 100 miles uses 4 gallons and costs $14.00, or $0.14 per mile in fuel. That excludes tolls and wear.
How do I calculate fuel cost per mile?
Cost per mile equals price per gallon divided by MPG, which is the same as total fuel cost divided by miles driven.
How do I calculate round-trip gas cost?
Enter the one-way distance and enable round trip, or enter the full round-trip miles with round trip off. Doubling both will overstate the trip.
How much do I spend on gas per month commuting?
Monthly miles = one-way miles × 2 × working days. Then monthly cost = monthly miles ÷ MPG × price per gallon. A 25-mile one-way commute, 22 days, 25 MPG, and $3.50/gal is $154.00 per month.
What MPG should I enter?
Use the average from your trip computer if you have it. Otherwise use a combined EPA rating from fueleconomy.gov and expect city driving to come in lower. SUV, sedan, truck, and hybrid chips are examples only.
How do I split gas cost between two passengers?
Calculate total fuel cost, then divide by the number of people paying. 100 one-way miles, round trip, 25 MPG, $3.50/gal, and two people is $28.00 total and $14.00 each.
Can I calculate diesel costs?
Yes. The formula is the same. Enter diesel MPG or L/100km and the diesel pump price. The calculator does not apply a gasoline-versus-diesel adjustment on its own.
Does this calculator include tolls?
No. Results are fuel only. Tolls, parking, food, hotels, and vehicle wear are separate.
Is the calculator accurate?
The math is exact for the numbers you enter. Real fuel use varies with speed, load, weather, and traffic. Add a consumption buffer if you expect extra use.
Can I use liters instead of gallons?
Yes. Switch distance to kilometers, efficiency to L/100km or km/L, and price to per liter. Unit switches keep the same physical values.
How do I convert MPG to L/100km?
L/100km = 235.215 ÷ US MPG, using a US gallon of 3.785411784 liters. Switching the efficiency unit in the calculator does this conversion for you.
Related Calculators
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