Fuel Savings Calculator
Compare yearly fuel costs of two vehicles.
Results update as you type.
How it works
When you are weighing a more fuel-efficient vehicle, the question that matters is how many dollars better MPG actually saves you each year, and this fuel savings calculator answers it directly. Enter your annual mileage, your current vehicle's fuel economy, the fuel economy of the vehicle you are considering, and the price of fuel, and the tool shows each car's yearly fuel bill and the savings between them. Seeing the two annual costs side by side turns an abstract MPG figure into money. Fuel economy improvements deliver diminishing returns: jumping from 15 to 20 MPG saves far more fuel than jumping from 40 to 45, even though both are five-MPG gains, because gallons burned depends on the reciprocal of MPG. This calculator captures that effect automatically, which helps you judge whether a more efficient car, a hybrid, or simply better driving habits justify their cost. The calculation is transparent and easy to test. It converts your annual miles into gallons for each vehicle, prices those gallons at the pump rate you enter, and subtracts to find the saving. Because mileage and fuel price are shared between the two, the entire difference reflects the change in efficiency. Try a higher fuel price, more annual miles, or a bigger MPG jump and watch the yearly saving grow, giving you a clear, personalised basis for deciding whether the switch pays off.
savings = (miles ÷ old MPG − miles ÷ new MPG) × fuel price
Each vehicle's yearly fuel cost is its annual mileage divided by its fuel economy, giving gallons burned, multiplied by the price per gallon. Dividing by a higher miles-per-gallon figure means fewer gallons and a smaller bill. Subtracting the more efficient vehicle's cost from the current one leaves the annual saving. Because the mileage and price are shared, the gap comes entirely from the difference in fuel economy between the two cars.
Source:U.S. EPA fuel economy
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter annual miles, current mpg, new mpg and fuel price.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Annual savings updates instantly as you type — no button to press.
Frequently asked questions
Why do fuel savings shrink at high MPG?
Fuel burned depends on the reciprocal of MPG, so gains matter most at the low end. Going from 15 to 20 MPG saves far more gallons than going from 40 to 45, even though both are five-MPG improvements. This is why a modest efficiency gain on a thirsty vehicle can save more money than a large gain on an already efficient one. The calculator captures this automatically through the miles-divided-by-MPG step.
What annual mileage should I enter?
Use the number of miles you realistically expect to drive in a year. Many drivers cover somewhere between 10,000 and 15,000 miles annually, but commutes, road trips, and work driving vary widely. If you are unsure, check your odometer against last year's figure or your service records. Higher mileage magnifies fuel savings, so using an accurate estimate keeps the comparison honest rather than overstating the benefit of switching.
Does this include the cost of buying the new vehicle?
No, this calculator compares only annual fuel costs between two fuel economy figures. It does not account for the purchase price, financing, insurance, or maintenance differences between the vehicles. Use the yearly fuel saving as one input into a bigger decision. To judge whether a more efficient car pays for itself, weigh the annual saving shown here against any extra upfront cost over the years you plan to keep it.
Can I use this to compare petrol and diesel or a hybrid?
Yes, as long as both vehicles use the same fuel priced per gallon, the comparison is straightforward. If the two use different fuels at different prices, this simple version, which shares one fuel price, will not be accurate. For a like-for-like efficiency comparison on the same fuel, or to test the effect of a hybrid's higher MPG, enter each vehicle's economy and see the yearly difference at your local fuel price.
How does fuel price affect the savings?
Fuel price scales the saving directly: the higher the price per gallon, the more each avoided gallon is worth, so the annual saving from better economy grows. When prices spike, an efficient vehicle's advantage widens, and when prices fall it narrows. Because the future price is uncertain, it is worth testing a few values, such as today's price and a higher one, to see how sensitive your savings are to the pump.