Fuel Cost per 100 Miles: A Better Way to Compare Cars
- Formula: Cost per 100 miles = (100 ÷ MPG) × price per gallon.
- Label shortcut: Cost per 100 miles = (gallons/100 miles) × price per gallon.
- Why it helps: It makes “MPG differences” comparable in real dollars (especially at higher MPG).
What “Cost per 100 Miles” Means
Cost per 100 miles is exactly what it sounds like: how much you pay in fuel to drive 100 miles. It is a helpful lens when you want to compare two vehicles (or two driving habits) without getting tripped up by how MPG behaves at higher numbers.
If you have not seen the “MPG illusion” before, it is worth reading next: Why MPG is not linear. The short version: moving from 15 to 20 MPG often saves more fuel than moving from 35 to 40 MPG over the same distance, even though both are “+5 MPG.”
What We Know (Sourced)
The EPA fuel economy label includes a fuel consumption rate expressed as gallons per 100 miles for gasoline vehicles. You can see this explained in EPA’s label documentation, including the interactive gasoline label and the text version of the gasoline label.
EPA also explains the purpose of the label as a standardized way to compare fuel economy, costs, and emissions across new vehicles. Source: U.S. EPA — Learn about the fuel economy label.
The Formula + Examples
If you already know your gallons per 100 miles, you can compute cost per 100 miles even faster:
| MPG (example) | Gas price (example) | Cost per 100 miles |
|---|---|---|
| 20 MPG | $3.50/gal | $17.50 |
| 30 MPG | $3.50/gal | $11.67 |
| 40 MPG | $3.50/gal | $8.75 |
How to Use It with the EPA Label
When comparing two vehicles, start with the EPA label (for a standardized baseline) and then personalize:
- Find the “fuel consumption rate” (gallons per 100 miles) on the label.
- Multiply by your local gas price to estimate your cost per 100 miles.
- Adjust for your driving mix using City/Highway MPG if your commute is very different from typical driving. (For background, see: EPA label basics and combined MPG weighting.)
Prefer an instant answer?
Use our calculator to estimate trip costs and fuel cost per distance in seconds.
Try the Fuel Cost CalculatorWhat’s Next (Practical Steps)
- Pick your comparison: two cars, two driving speeds, or two routes.
- Compute cost per 100 miles for each scenario.
- Scale to your life: multiply by your weekly miles or annual miles to estimate budget impact.
Once you have cost per 100 miles, you can also compute cost per mile easily. That is covered in: Cost per mile fuel formula.
Why It Matters
MPG is great for quick comparisons, but dollars are what you actually budget. Because EPA already publishes standardized label information (including consumption rate) for new vehicles, cost per 100 miles is a practical way to connect the label to your real fuel price. Sources: EPA gasoline label and EPA label overview.
Frequently Asked Questions
Is cost per 100 miles better than MPG?
It is not a replacement for MPG, but it is often easier for budgeting and comparing savings. Cost per 100 miles uses the same underlying info (fuel used per distance) and connects directly to your local fuel price.
Where do I find gallons per 100 miles on the EPA label?
On gasoline vehicle labels, EPA includes a “fuel consumption rate” in gallons per 100 miles. See EPA’s label documentation: interactive label or text label.
Can I use this for hybrids or EVs?
Yes, but the units may differ. Gasoline vehicles often show gallons/100 miles, while EV labels use electricity units (such as kWh). If you are comparing EV efficiency, start with: What is MPGe? and kWh per 100 miles.