Gas Cost Calculator Formula
Understand the math behind the gas cost calculator. Each variable explained with a worked example.
Formulas Used
Total Fuel Cost
total_fuel_cost = gallons_needed * gas_priceGallons Used
gallons_used = gallons_neededCost Per Mile
cost_per_mile = gas_price / mpgVariables
| Variable | Description | Default |
|---|---|---|
trip_miles | Trip Distance(miles) | 300 |
mpg | Vehicle MPG(MPG) | 28 |
gas_price | Gas Price Per Gallon(USD/gal) | 3.5 |
gallons_needed | Derived value= trip_miles / mpg | calculated |
How It Works
How to Calculate Gas Cost
Divide the trip distance by your MPG to find gallons needed, then multiply by the gas price.
Formula
Gallons = Distance / MPG
Fuel Cost = Gallons x Price Per Gallon
Worked Example
300-mile trip in a car getting 28 MPG with gas at $3.50/gallon.
- 01Gallons needed = 300 / 28 = 10.71 gal
- 02Fuel cost = 10.71 x $3.50 = $37.50
- 03Cost per mile = $3.50 / 28 = $0.125
Frequently Asked Questions
How do I find my car's MPG?
Check the EPA fuel economy sticker or fueleconomy.gov. You can also calculate it by filling up, driving, and dividing miles driven by gallons to refill.
Does highway vs city driving matter?
Yes, highway driving is generally 20-30% more fuel efficient than city driving due to less braking and acceleration.
How do I improve my fuel economy?
Drive at steady speeds, avoid rapid acceleration, keep tires inflated, remove excess weight, and use cruise control on highways.
Learn More
Guide
Fuel Economy Guide - Understanding MPG and Fuel Costs
Learn how to calculate fuel economy, compare MPG ratings, and estimate trip fuel costs. Covers miles per gallon, liters per 100 km, and money-saving driving tips.
Ready to run the numbers?
Open Gas Cost Calculator