Monthly Fuel Cost Calculator
Fuel is one of the most predictable yet easily overlooked lines in a household budget, and this monthly fuel cost calculator turns three simple numbers into a clear estimate of what you spend at the pump. Enter the miles you drive in a typical month, your vehicle's miles-per-gallon figure, and the price you pay per gallon. The tool divides your miles by your mpg to find the gallons you burn, multiplies by the pump price to give the monthly cost, and then scales that up to an annual figure so you can see the bigger picture. It is a handy way to compare two cars, plan a budget, or check how a change in gas prices or commute distance would hit your wallet. Because fuel economy in the real world depends on traffic, terrain, weather and driving style, and because prices differ by region and shift over time, every input is left fully editable rather than assumed for you. The math is deliberately transparent: a single division followed by a multiplication, shown in the formula section below, with a worked example that reconciles exactly to the calculator defaults so you can follow and trust each step.
Monthly fuel cost is gallons used times the pump price: cost = (miles / mpg) x price. Driving 1,000 miles a month at 25 mpg and $3.50 a gallon costs $140.00 a month, about $1,680.00 a year.
Monthly fuel cost formula
Gallons = M / E
Monthly cost = Gallons x P
Annual cost = Monthly cost x 12
M = monthly miles, E = miles per gallon
P = price per gallon
Dividing miles by mpg gives the gallons consumed, and multiplying by the price per gallon turns those gallons into dollars. Multiplying the monthly figure by twelve gives the annual cost.
Worked example
You drive 1,000 miles a month, your car returns 25 mpg, and gas costs 3.50 a gallon.
- Gallons used = 1,000 / 25 = 40 gallons
- Monthly cost = 40 x 3.50 = 140.00
- Annual cost = 140.00 x 12 = 1,680.00
You spend about 140.00 a month, or 1,680.00 a year, on fuel. These are the calculator's default inputs, so the result above matches the widget exactly.
Monthly fuel cost calculator: frequently asked questions
How do I calculate my monthly fuel cost?
Divide the miles you drive in a month by your vehicle's miles per gallon to find the gallons you burn, then multiply by the price per gallon. For example, 1,000 miles at 25 mpg uses 40 gallons, and at 3.50 a gallon that is 140 a month. This calculator does the arithmetic for you and also shows the annual total by multiplying the monthly figure by twelve.
Where do I find my vehicle's mpg?
Your car's combined fuel economy is usually printed on the original window sticker and listed in the owner's manual. Real-world mpg often differs from the rating because of driving style, traffic, terrain and weather, so for the most accurate result, track your own miles and gallons over a few fill-ups and use that figure. The calculator accepts whatever mpg you enter.
Does fuel price change the result a lot?
Yes. Fuel price is a direct multiplier, so a swing in the pump price moves your monthly cost proportionally. If the price rises from 3.50 to 4.00 a gallon, the same driving costs about 14% more. Because prices vary by region and over time, the calculator leaves price as an editable input so you can test different scenarios.
How can I cut my monthly fuel spend?
The two biggest levers are driving fewer miles and improving real-world fuel economy. Combining trips, keeping tyres properly inflated, removing roof racks, easing off hard acceleration and maintaining the engine all help mpg. Choosing a more efficient vehicle has the largest long-term effect, since it lowers the gallons used for every mile you drive.
What is the monthly fuel cost formula?
Monthly cost equals monthly miles divided by miles per gallon, multiplied by the price per gallon. With 1,000 miles, 25 mpg and 3.50 per gallon, that is 1,000 / 25 = 40 gallons, times 3.50, which equals 140.00 a month, or 1,680.00 a year.
Official sources
- Transportation and commuting cost guidance: US Centers for Disease Control and Prevention (CDC). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.