Fuel Needed for a Trip Calculator
Work out how many gallons a trip needs from the distance and your fuel economy — plus the cost and how many fill-ups it takes.
How it works
Gallons needed = distance ÷ mpg · Cost = gallons × price · Tanks = gallons ÷ tank capacity · Refuel stops ≈ ⌈tanks⌉ − 1
The gallons a trip consumes is just distance divided by fuel economy; multiplying by the pump price gives the cost. Dividing the fuel by your tank size shows how many tankfuls the trip takes, and starting from a full tank you need one fewer stop than the number of tanks — the first tank is already aboard. Plan refuels a little early so you are not hunting for a station on the last few miles.
Worked example
A 600-mile trip at 28 mpg needs 600 ÷ 28 ≈ 21.4 gallons. At $3.50 a gallon that is about $75. With a 14-gallon tank the trip is roughly 1.5 tankfuls, so starting full you need one refuel stop along the way.
Frequently asked questions
How much fuel do I need for a long drive?
Divide the total miles by your car’s MPG to get gallons, then check that against your tank size to plan stops. Add a little margin for detours, traffic and lower-than-rated economy, especially in mountains, heat or headwinds.
Why plan to refuel before the tank is empty?
Fuel gauges are approximate and stations can be spaced far apart on rural interstates. Refueling around a quarter tank protects your fuel pump and guarantees you are never stranded between exits — a small buffer beats a roadside wait.
Does a heavy load change how much fuel I need?
Yes. Extra passengers, cargo, roof boxes and trailers raise the energy needed to move the car, cutting MPG and increasing the gallons a trip requires. For loaded or towing trips, use a lower MPG figure than your usual solo number.
Related calculators
Educational estimate — real-world figures vary with load, temperature, traction, tuning and measurement method.