Gallons per 100 Miles Explained (Fuel Consumption Rate)
- MPG answers “How far can I go on a gallon?”
- Gallons/100 miles answers “How much fuel do I use to go 100 miles?”
- Fuel cost per 100 miles is simple: (gallons/100 miles) × (price per gallon).
Most drivers think in MPG, but MPG is not always the easiest way to compare fuel use. That is why the EPA label includes a fuel consumption rate expressed as gallons per 100 miles. EPA’s interactive gasoline label explains that this metric relates directly to fuel used and fuel expenditures.
What Gallons/100 Miles Means
Gallons per 100 miles answers a simple question:
It is closely related to MPG, but it’s expressed in a way that makes fuel use and fuel cost easier to see.
Where You See It (EPA Label)
On gasoline vehicles, the fuel economy label includes a “Fuel Consumption Rate” section that shows estimated gallons/100 miles for combined city and highway driving. EPA explains this directly in the interactive label and also in the text version of the gasoline label.
If you want the big picture of how City, Highway, and Combined MPG fit into this, see: Understanding the EPA fuel economy label.
How to Convert MPG to Gallons/100 Miles
For US units, the conversion is straightforward math:
If you prefer metric units, the common fuel consumption metric is L/100km. We cover conversions in detail here: MPG to L/100km conversion.
Why This Metric Is Helpful
Gallons/100 miles is useful because it’s linear with fuel used. When gallons/100 miles drops by 1 gallon, you really do burn 1 less gallon over 100 miles. MPG doesn’t behave that way, which is why people sometimes get misled when they compare “MPG gains” across very different vehicles (see: The MPG illusion explained).
| MPG | Gallons/100 miles | Fuel used over 10,000 miles |
|---|---|---|
| 20 | 5.0 | 500 gallons |
| 25 | 4.0 | 400 gallons |
| 33 | 3.03 | 303 gallons |
| 50 | 2.0 | 200 gallons |
Those fuel-used numbers are just math, but the key point is practical: gallons/100 miles makes it easier to translate label efficiency into budget impact.
How to Calculate Cost per 100 Miles
Once you have fuel consumption, cost per 100 miles is simple:
If you’d rather compute fuel cost on a per-mile basis (useful for commuting and comparing cars), try:
Calculate Your Fuel Cost per Mile
Enter your gas price and MPG to get a clear fuel cost per mile (and per year).
Use the Cost Per Mile CalculatorFrequently Asked Questions
Is gallons per 100 miles on every EPA label?
For gasoline vehicles, EPA’s interactive label describes a “Fuel Consumption Rate” shown in gallons per 100 miles for combined driving. See EPA’s interactive gasoline label.
Is gallons/100 miles the same as L/100km?
They are similar ideas (fuel used per fixed distance) but use different units. Gallons/100 miles is a US-unit metric. L/100km is the common metric-unit version. See our conversion guide: MPG to L/100km.
Why does EPA include fuel consumption on the label?
EPA explains that consumption relates directly to fuel used and fuel expenditures, which can make comparisons more intuitive than MPG alone. That explanation is included in the interactive gasoline label.
How do I use this to plan a road trip?
For trips, you can estimate gallons needed as Distance ÷ MPG and multiply by price per gallon. Our guide How to calculate fuel cost for a road trip walks through the steps.