Fuel Cost Calculator

Estimating fuel cost for a trip looks simple on paper, but the number people plug in for "fuel efficiency" is usually the least reliable part of the calculation — real-world conditions routinely knock 10–30% off a vehicle's rated MPG.

The Basic Fuel Cost Formula

Why Your Real-World MPG Rarely Matches the Sticker

The EPA rating on a new car's window sticker is measured under controlled lab conditions — it's a useful baseline for comparing vehicles, but not a precise predictor of what you'll actually get on a given trip. Several factors commonly cause real efficiency to run lower:

• Highway speed. Aerodynamic drag increases roughly with the square of speed, which is why fuel economy tends to drop noticeably above 60–65 mph — a car cruising at 75 mph can burn 15–20% more fuel per mile than the same car at 60 mph.
• Terrain. Sustained uphill driving burns significantly more fuel than flat terrain, and while descents partially recover some of that loss, mountainous routes typically still average lower MPG than flat ones over a full round trip.
• Climate control. Running air conditioning can reduce fuel economy by roughly 5–25%, with the largest impact in stop-and-go city driving where the engine is already working harder relative to its output.
• Cargo and tire pressure. Extra weight and underinflated tires both increase rolling resistance — underinflated tires alone can reduce fuel economy by about 1% for every 1 PSI drop below the recommended level.

Comparing Cost Per Mile: Gas vs. Electric

For a more useful cross-vehicle comparison, convert everything to a cost per mile basis.

In this example, the EV costs less than half as much per mile to fuel — though the comparison should also account for charging losses (typically 10–15% above the vehicle's rated consumption) and the fact that home charging rates are usually cheaper than public fast-charging rates.

Practical Ways to Lower Fuel Costs

• Route comparison matters more than gas station comparison. A route that's 15 miles shorter often saves more than hunting for gas that's a few cents cheaper per gallon, once the detour to reach it is factored in.
• Combine trips. A cold engine uses more fuel per mile for the first several minutes of a drive, so several short separate trips typically cost more in total fuel than the same errands combined into one route.
• Maintain tire pressure and get regular tune-ups. These are the lowest-effort, most reliably measurable efficiency gains available to any driver, regardless of vehicle type.