EZ Calculators

Gas Calculator

Use this gas calculator to price a drive before you leave. Enter the one-way distance, your car's MPG and the gas price. You'll get gallons needed, total fuel cost, cost per mile and an even split for everyone riding along, with tolls and parking added if you like.

Calculation and content reviewed by EZ Calculators Editorial Team on .

Enter values

Build a one-way or round-trip fuel budget from route distance, repeat trips, a visible detour allowance, your vehicle's fuel-use basis, and the price volume used at the pump. Optional costs and travelers stay separate from fuel arithmetic.

Build the scenario below, then calculate for a complete result report.

Runs in your browser
Choose the route planDistance is entered for one direction. Round trip doubles it before repeat trips and route allowance are applied.

Define the distance being budgeted

Repeat trips multiply the route. The optional allowance adds distance for known detours or local driving without changing vehicle efficiency.
Enter the mapped or measured distance in one direction.
A round trip counts as one trip in this field.
Optional distance for detours or local driving. This changes route distance, not vehicle efficiency.
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Match the vehicle rating and pump price units

US MPG and Imperial MPG are different gallon systems. The unit controls beside each value keep the conversion explicit.
Use a measured trip value when available; a label rating is a comparison estimate.
Use the price you expect to pay, in the selected volume unit.

Keep fuel, other costs, and sharing separate

Other costs are added once across the complete plan. Equal sharing divides the combined entered total by the traveler count.
Use a current, clearly labeled basis

This page does not fetch fuel prices or promise real-world consumption. Use the price you expect to pay and, when available, a measured efficiency from driving conditions similar to the planned route.

How much will gas cost for my trip?

Divide the total miles by your car's MPG to get gallons, then multiply by the price per gallon. A 250-mile drive each way is 500 miles round trip. At 28 MPG that's 17.86 gallons, and at $3.75 a gallon the gas costs $66.96. Split four ways, each person pays $16.74.

How to use the gas calculator

Enter the distance one way. Choose Round trip and the return leg is added for you, so don't double it yourself.

Use your real MPG if you know it. The window sticker figure is a lab rating, and highway speed, traffic, cargo and weather all change what you get on the road.

  1. Enter the one-way distance in miles or kilometers, and pick one way or round trip.
  2. Set the number of identical trips, such as 20 commutes, and an optional extra percentage for detours.
  3. Enter fuel economy as U.S. MPG, Imperial MPG, km/L or L/100 km.
  4. Enter the gas price and whether it's per U.S. gallon, Imperial gallon or liter.
  5. Add tolls or parking as a total, set how many people share the cost, and press Calculate gas cost.

Gas money calculator: splitting the cost

Set the number of travelers and the calculator divides the cost evenly. It shows two figures per person: the gas alone and gas plus whatever tolls or parking you entered.

On the 500-mile round trip above, with $20 in tolls and four people, the gas is $16.74 each and the full share is $21.74 each. If the driver isn't paying a share, set travelers to the number of passengers instead.

Gas money for a 500-mile round trip at 28 MPG and $3.75 per gallon
PeopleGas per personGas plus $20 tolls, per person
1$66.96$86.96
2$33.48$43.48
3$22.32$28.99
4$16.74$21.74

Trip gas cost formula

Distance comes first. One-way miles are doubled for a round trip, multiplied by the number of trips, and then raised by any detour allowance. Fuel is that distance over MPG. Cost is fuel times price.

Formula guide
  • Planned miles = one-way miles x (2 for round trip) x trips x (1 + allowance % / 100)
  • Gallons needed = planned miles / MPG
  • Gas cost = gallons needed x price per gallon
  • Cost per person = (gas cost + other costs) / travelers

Worked fuel cost examples

Each row below came from the calculator. The commute row shows why repeated trips add up: $3.50 a day becomes $70 over 20 workdays.

Fuel cost examples
TripFuel economy and priceFuel neededGas cost
100 mi each way, round trip25 MPG, $3.50/gal8 gal$28.00
15 mi commute each way, 20 round trips30 MPG, $3.50/gal20 gal$70.00
200 mi one way plus 10% detours30 MPG, $4.00/gal7.33 gal$29.33
250 mi each way, round trip22 MPG, $3.75/gal22.73 gal$85.23
300 km one way7.5 L/100 km, EUR 1.80/L22.5 LEUR 40.50

Gas cost per mile

Price per gallon divided by MPG gives the cost of gas for each mile. At $3.75 and 28 MPG it's about 13 cents a mile. Drop to 22 MPG and it's about 17 cents. The result shows this figure for every trip, in both miles and kilometers.

That number is gas only. The IRS standard mileage rate is much higher because it also covers wear, maintenance, insurance and depreciation, so don't compare the two directly.

Formula guide
  • Gas cost per mile = price per gallon / MPG

MPG, Imperial MPG and L/100 km

A U.S. gallon is 3.785411784 liters and an Imperial gallon is 4.54609 liters. So a car doing 28 MPG in U.S. gallons does about 33.6 MPG in Imperial gallons, with the same fuel use. Mixing a UK MPG figure with a U.S. gas price makes the trip look cheaper than it is.

L/100 km runs the other way: lower is better. Natural Resources Canada gives the quick conversion of 235.21 divided by L/100 km for U.S. MPG. The calculator handles every combination and shows the equivalents.

Limits and when to double-check

The estimate is only as good as the MPG and price you enter. According to the EPA, speed, traffic, terrain, weather, load and tire pressure all move real mileage. To show the range, the result includes a table from 20% less to 20% more fuel use.

The tool doesn't look up live gas prices or routes. For work mileage claims, use your employer's policy or the IRS rate, not this gas-only figure.

Sources

These sources back the fuel economy, unit and mileage-rate points on this page.

US EPA: Your Mileage May VaryWhy traffic, speed, weather and load change real fuel economy.Natural Resources Canada: understanding the tablesConversions between L/100 km, U.S. MPG and Imperial MPG.UK Vehicle Certification Agency: fuel costAn Imperial MPG fuel cost method using the Imperial gallon.IRS: standard mileage ratesOfficial per-mile rates that cover the full cost of driving.NIST SP 811 Appendix B.8 conversion factorsExact gallon, liter and mile definitions used in the math.

FAQ

How much gas money should I give a driver?

Work out the gas cost for the trip and divide by the number of people, usually including the driver. A $66.96 round trip split four ways is $16.74 each. Some groups also chip in for tolls, parking or wear on the car.

How many gallons of gas will I use on a 500-mile trip?

Divide 500 by your MPG. At 28 MPG it's about 17.86 gallons, at 25 MPG it's 20 gallons, and at 22 MPG it's about 22.73 gallons.

Should I enter the round-trip distance?

No. Enter the one-way distance and pick Round trip. The calculator doubles it for you. If you type the round-trip miles and also choose Round trip, you'll get double the real cost.

How much does it cost to drive 100 miles?

Divide 100 by your MPG and multiply by the gas price. At 25 MPG and $3.50 a gallon, that's 4 gallons and $14. At 30 MPG it's about $11.67.

Can I use this for a daily commute?

Yes. Enter the one-way commute, choose Round trip, and set identical trips to the number of workdays. A 15-mile commute at 30 MPG and $3.50 a gallon costs $70 for 20 days.

Does the fuel cost include tolls?

Only if you enter them. Put the total for tolls, parking or ferries in Other trip costs. They're kept separate from fuel and added into the per-person share.

What if my car's MPG is in UK gallons?

Choose MPG (Imperial gallon). A UK gallon is about 20% bigger than a U.S. gallon, so the same car shows a higher MPG number. The calculator converts it before pricing the fuel.