Fuel Savings Calculator
Enter your current MPG, the MPG you want to compare it with, the miles you drive a month and a gas price. The calculator prices the same monthly miles at both MPG figures and shows the monthly difference and the yearly one (monthly × 12). It compares fuel cost only, and it keeps the miles the same for both; to price driving fewer miles, run it once for each mileage.
How to Use This Calculator
- 1
Enter miles per month
The miles box is monthly. Divide yearly miles by 12 (12,000 a year is 1,000 a month), or multiply weekly miles by 52 and divide by 12 (300 a week is 1,300 a month).
- 2
Use your measured MPG for the current car
An average you measured with the Mileage (MPG) Calculator reflects your own driving. For the other car, use the rating that matches your mix of city and highway miles.
- 3
Run it twice to price driving less
Both MPG figures use the same miles. To price a cut in miles, enter the same MPG in both boxes, run each mileage, and compare the Current Monthly Cost results.
Formula and Logic
The calculator works out the gallons each MPG figure needs for the same distance, prices the difference, and multiplies the monthly result by 12 for the year.
Current fuel use
Distance ÷ Current MPG = gallons used now
Improved fuel use
Distance ÷ Improved MPG = gallons used after change
Fuel saved
Current fuel use − Improved fuel use = gallons saved
Money saved
Gallons saved × Fuel price = dollars saved
Yearly savings
Dollars saved per month × 12 = dollars saved per year
Why equal MPG gains are not worth the same
- •Over 1,000 miles, going from 20 to 25 MPG saves 10 gallons, but going from 40 to 45 MPG saves only about 2.8.
- •The dollar value moves with the price: 10 gallons saved is worth $30 at an example $3.00 a gallon and $40 at $4.00.
Example Calculations
Example 1: Improving fuel economy
Inputs
- Monthly distance1,000 miles
- Current MPG20
- Improved MPG25
- Fuel price$4.00/gal
Calculation Steps
- Current fuel use1,000 ÷ 20 = 50 gal
- Improved fuel use1,000 ÷ 25 = 40 gal
- Fuel saved50 − 40 = 10 gal
- Current cost50 × $4 = $200
- New cost40 × $4 = $160
That is $480 a year, the Annual Savings figure the calculator shows (monthly × 12).
$40 saved per monthExample 2: Driving less each week
Inputs
- Current weekly distance300 miles
- New weekly distance240 miles
- Fuel economy30 MPG
- Fuel price$3.50/gal
Calculation Steps
- Current fuel use300 ÷ 30 = 10 gal
- New fuel use240 ÷ 30 = 8 gal
- Fuel saved10 − 8 = 2 gal
- Current cost10 × $3.50 = $35
- New cost8 × $3.50 = $28
Over 52 weeks that is $364 a year.
$7 saved per weekExample 3: Better mileage and lower travel distance
Inputs
- Current monthly distance1,200 miles
- New monthly distance1,000 miles
- Current MPG24
- Improved MPG32
- Fuel price$3.80/gal
Calculation Steps
- Current fuel use1,200 ÷ 24 = 50 gal
- New fuel use1,000 ÷ 32 = 31.25 gal
- Fuel saved50 − 31.25 = 18.75 gal
- Current cost50 × $3.80 = $190
- New cost31.25 × $3.80 = $118.75
Cutting 200 miles at 24 MPG saves about $31.67, and the MPG change on the remaining 1,000 miles saves about $39.58. Together that is $71.25 a month, or $855 a year.
$71.25 saved per monthThe calculator holds miles fixed, so for Examples 2 and 3 run each mileage separately and compare the Current Monthly Cost results.
Annual savings upgrading from 25 MPG: 1,000 miles/month at an example $3.45/gal
How Small Savings Add Up Over a Year
A driver covering 1,200 miles a month who moves from a 22 MPG car to a 28 MPG car cuts fuel use from about 54.5 gallons to about 42.9 gallons a month. At an example price of $3.80 a gallon, that saves about $44 a month, or about $530 a year, with no change in how far they drive.
Trim another 100 miles a month by combining errands and the yearly figure grows again. Neither change looks dramatic in a single month, which is why the yearly result is the one worth comparing against a car payment or a repair bill.