# How much will gas cost?

Computes the fuel a trip uses and what it costs from the distance, the fuel economy in mpg, L/100 km or km/L, and the price per gallon or litre, with a round trip and a split between people.

- Page: https://www.acalculator.org/everyday-life/gas-calculator
- JSON spec: https://www.acalculator.org/everyday-life/gas-calculator.json
- Version: a72cd4680f30

## Default answer

Example with the default inputs (Distance 250 mi, Round trip No, Fuel economy 25, Fuel economy unit mpg (US), Fuel price $4.48, Price per Gallon (US), Split between 1): Driving 250 mi uses 10 gal of fuel, which costs $44.78.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| dist | Distance | How far the trip is, one way. |
| round | Round trip | Count the distance twice, there and back. |
| econ | Fuel economy | How far the car goes on its fuel, in the unit chosen next. |
| econUnit | Fuel economy unit | Miles per US gallon, litres per 100 kilometres, or kilometres per litre. |
| price | Fuel price | The price of the fuel per gallon or per litre. |
| per | Price per | Whether the price is per US gallon or per litre. |
| people | Split between | How many people share the cost. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| cost | Fuel cost | The fuel used × the price. |
| fuel | Fuel used | The distance ÷ the fuel economy. |
| liters | Fuel used (litres) | The fuel used in litres. |
| share | Cost per person | The fuel cost ÷ the number of people. |
| total | Distance driven | The distance, doubled for a round trip. |

## Method

fuel = distance ÷ fuel economy (or distance × L/100 km ÷ 100); cost = fuel × price per unit of fuel

## Assumptions

- The fuel economy is the car’s average for the trip. Speed, load, traffic and weather change it.
- mpg is miles per US gallon (3.785411784 L). L/100 km and km/L are converted exactly.
- The default price is the US average for regular gasoline in the week of September 21, 2026, from the EIA. Type your local price.

## Worked examples

1. dist = 24,140,160, round = no, econ = 20, econUnit = mpg, price = $3.60, per = gal, people = 1 gives fuel = 2.839059, cost = $2,700.00. Source: fueleconomy.gov, Fuel Economy Savings Calculator (cited in content.mdx): 15,000 miles at 20 mpg and $3.60 a gallon; 15,000 ÷ 20 = 750 gal × $3.60 = $2,700 (hand calculation in content.mdx).
2. dist = 24,140,160, round = no, econ = 30, econUnit = mpg, price = $3.60, per = gal, people = 1 gives fuel = 1.892706, cost = $1,800.00. Source: fueleconomy.gov, Fuel Economy Savings Calculator: the 30 mpg car costs $900 less a year than the 20 mpg car; 15,000 ÷ 30 = 500 gal × $3.60 = $1,800.
3. dist = 300,000, round = yes, econ = 7.5, econUnit = l100km, price = $1.80, per = L, people = 3 gives fuel = 0.045, cost = $81.00, share = $27.00. Source: hand calculation in content.mdx: 600 km × 7.5 ÷ 100 = 45 L; × $1.80 = $81; ÷ 3 = $27.
4. dist = 120,000, round = no, econ = 15, econUnit = kml, price = $4.48, per = gal, people = 1 gives fuel = 0.008, cost = $9.46. Source: hand calculation in content.mdx: 120 ÷ 15 = 8 L = 2.113 gal; × $4.478 = $9.46.

## FAQ

### How do I calculate the gas cost of a trip?

Divide the distance by your mpg to get gallons, then multiply by the price per gallon. 250 miles at 25 mpg is 10 gallons; at $4.478 a gallon that is $44.78.

### How do I use L/100 km?

L/100 km is litres used per 100 kilometres. Fuel = distance in km × L/100 km ÷ 100. A 600 km round trip at 7.5 L/100 km uses 600 × 7.5 ÷ 100 = 45 L.

### How much does better fuel economy save?

fueleconomy.gov shows that at 15,000 miles a year and $3.60 a gallon, a 30 mpg car costs $900 a year less to fuel than a 20 mpg car: 500 gallons ($1,800) against 750 gallons ($2,700).

### What price does the calculator start with?

The US average retail price of regular gasoline for the week of September 21, 2026, $4.478 a gallon, from the U.S. Energy Information Administration. Prices change every week and differ by state, so type the price at your pump.

### How do I split gas money with friends?

Enter how many people share the ride in Split between. The calculator divides the fuel cost equally. It does not add tolls, parking or wear on the car.

### Why does my real fuel use differ?

Rated mpg is measured on set test cycles. Highway speed, air conditioning, a full load, cold weather and traffic all change it, so use the average your car shows for trips like this one if you have it.

## Sources

- U.S. Department of Energy and U.S. EPA, fueleconomy.gov, Fuel Economy Savings Calculator: fuel cost = miles ÷ mpg × price per gallon. https://www.fueleconomy.gov/feg/savemoney.jsp
- U.S. Energy Information Administration, Gasoline and Diesel Fuel Update: US regular gasoline $4.478 a gallon, week of September 21, 2026. https://www.eia.gov/petroleum/gasdiesel/
- NIST SP 811 (2008), Appendix B: 1 US gallon = 3.785411784 L exactly; 1 mi = 1.609344 km exactly.