Cost per mile
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Fuel Cost Calculator
How much will your road trip cost in gas? How much do you save by driving across town for cheaper fuel? One calculator, all the answers.
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Enter price, MPG, distance
Tank fill-up
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Gallons needed
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The math
Total trip cost = (distance ÷ MPG) × price-per-gallon. Cost per mile = price-per-gallon ÷ MPG. These two numbers are the most useful way to think about fuel — MPG alone is meaningless without knowing what you pay per gallon. A 25 MPG car at $3.50/gal and a 50 MPG hybrid at $3.50/gal differ by exactly $0.07 per mile.
Real-world tips
Dropping highway speed from 70 mph to 60 mph saves ~15% on fuel. Check tire pressure monthly — under-inflation costs 3–4% MPG. Driving across town for $0.10 cheaper gas is usually worth it if the station is within 2–3 miles (at 28 MPG and 14-gallon tank you save $1.40 per fill).
Frequently asked questions
What is my real MPG?
Track several fill-ups: reset trip meter, fill to same click each time, divide miles by gallons added. EPA sticker MPG is often 10–20% optimistic.
Worth driving out of the way for cheaper gas?
Divide price diff by MPG to get $ saved per tank, subtract gas spent on the extra miles. At $0.10 cheaper / 28 MPG / 14 gal tank = $1.40 saved. A 2-mile detour costs ~$0.25 gas — worth it.
Diesel vs gas?
Enter both prices with both MPGs and compare cost-per-mile. Diesels are 25–35% more efficient but fuel is pricier in the US.
Does AC hurt MPG?
Yes — especially at low speeds (5–20% hit). Above 55 mph, open windows use more fuel than AC.
How accurate is this?
As accurate as your inputs. Biggest variable is real-world MPG (speed, weather, traffic, maintenance).
Last updated
For general calculations only. Not financial, tax, or legal advice — see our disclaimer.