Fuel Efficiency Calculator Formula
Understand the math behind the fuel efficiency calculator. Each variable explained with a worked example.
Formulas Used
Vehicle A Annual Fuel
annual_cost_a = cost_aVehicle B Annual Fuel
annual_cost_b = cost_bAnnual Savings (B vs A)
annual_savings = cost_a - cost_b5-Year Savings
five_year_savings = (cost_a - cost_b) * 5Variables
| Variable | Description | Default |
|---|---|---|
annual_miles | Annual Miles Driven(miles) | 12000 |
gas_price | Gas Price(USD/gal) | 3.5 |
mpg_a | Vehicle A MPG(MPG) | 25 |
mpg_b | Vehicle B MPG(MPG) | 35 |
cost_a | Derived value= annual_miles / mpg_a * gas_price | calculated |
cost_b | Derived value= annual_miles / mpg_b * gas_price | calculated |
How It Works
How to Compare Fuel Efficiency
Calculate each vehicle's annual fuel cost and find the difference.
Formula
Annual Fuel Cost = Annual Miles / MPG x Gas Price
Savings = Cost A - Cost B
Worked Example
12,000 miles/year at $3.50/gal: Vehicle A gets 25 MPG, Vehicle B gets 35 MPG.
- 01Vehicle A cost = 12,000 / 25 x $3.50 = $1,680
- 02Vehicle B cost = 12,000 / 35 x $3.50 = $1,200
- 03Annual savings = $1,680 - $1,200 = $480
- 045-year savings = $480 x 5 = $2,400
Frequently Asked Questions
Is a 10 MPG improvement always worth it?
The value depends on your starting point. Going from 15 to 25 MPG saves much more fuel than going from 35 to 45 MPG for the same miles driven.
Should fuel cost be the only factor when choosing a car?
No. Consider purchase price difference, insurance, maintenance, reliability, comfort, and resale value alongside fuel economy.
How many miles does the average American drive?
About 13,500 miles per year, or roughly 37 miles per day.
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 Fuel Efficiency Calculator