How to calculate gas savings from MPG
Divide annual miles by each vehicle's MPG to find gallons used, then multiply by the price per gallon. Subtract the new vehicle's annual fuel cost from the current vehicle's cost.
Annual fuel cost = annual miles ÷ MPG × price per gallon
For two vehicles using the same fuel price, annual gas savings = annual miles × (1 ÷ current MPG − 1 ÷ new MPG) × price per gallon. Use your measured MPG or look up vehicle estimates with the U.S. Department of Energy and EPA fuel cost comparison.
51 MPG vs 26 MPG: yearly savings example
Assume 12,000 miles per year and an illustrative gasoline price of $3.50 per gallon for both vehicles.
| Vehicle efficiency | Annual gasoline cost |
|---|---|
| 26 MPG | $1,615.38 |
| 51 MPG | $823.53 |
The 51 MPG vehicle saves about $792 per year, or $66 per month, on gasoline under these assumptions. Enter 26 and 51 MPG above, with 12,000 annual miles and $3.50 gasoline, to explore this scenario. Set maintenance and insurance differences to zero to isolate fuel savings.
Compare gasoline, hybrid, and electric car costs
For a gasoline hybrid, enter MPG and the gasoline price. For an EV, select Electric and enter efficiency in miles per kWh. Annual electricity cost = annual miles ÷ miles per kWh × electricity price per kWh. For example, 12,000 miles at 4 miles per kWh and $0.15 per kWh costs $450 per year for electricity.
The calculator compares cumulative operating savings with the vehicle price minus trade-in value to estimate payback. Energy-price growth, maintenance, and insurance can change that timeline. Financing costs and future resale values are outside this model.
Check your purchase budget with the car affordability calculator, estimate financing with the auto loan calculator, or compare payment options in the lease vs buy calculator.