Truck MPG to Gallons per 100 Miles: Conversion Reference Table

To convert truck MPG to US gallons per 100 miles, divide 100 by the MPG value. For example, 6.5 MPG equals approximately 15.38 US gallons per 100 miles.

MPG measures distance traveled per gallon; gallons per 100 miles measures fuel consumed over a fixed distance. Higher MPG means lower fuel consumption, while a lower gallons-per-100-miles value means less fuel used for the same distance. FuelEconomy.gov explains why consumption-based measurements help compare fuel use more directly than MPG differences alone.

MPG-to-Gallons-per-100-Miles Table

All gallons in this table are US liquid gallons, not Imperial gallons. The values are conversions, not typical truck MPG figures, performance targets, or predictions of actual fuel use.

Values are calculated as 100 ÷ MPG and rounded to two decimal places. The displayed precision describes the conversion; it does not imply that a truck’s measured fuel economy is equally precise.

Conversion Formulas

For a positive MPG value:

[
\text{US gallons per 100 miles} = \frac{100}{\text{MPG}}
]

To convert back:

[
\text{MPG} = \frac{100}{\text{US gallons per 100 miles}}
]

For example:

[
100 \div 6.5 = 15.3846\ldots \approx 15.38 \text{ US gal/100 mi}
]

These are reciprocal measurements: doubling MPG halves fuel consumption over the same distance. Equal increases in MPG do not represent equal gallon savings—a relationship illustrated in FuelEconomy.gov’s explanation of fuel consumption rates.

Zero MPG cannot be used in the first formula because division by zero is undefined. Negative values are not meaningful for this reference.

Estimate Fuel Use for a Trip

Use the original MPG value, rather than a rounded table entry, when estimating gallons for a specific distance:

[
\text{Estimated US gallons} = \frac{\text{Trip miles}}{\text{Expected MPG}}
]

As a hypothetical example, a 1,000-mile trip at an assumed 6.5 MPG would require:

[
1{,}000 \div 6.5 \approx 153.85 \text{ US gallons}
]

Multiplying the rounded table value of 15.38 by ten gives 153.80 gallons. That small difference comes from rounding; retaining the original MPG avoids it.

Use all miles covered by the estimate, including loaded and deadhead miles when estimating fuel for the full trip. The result assumes that the selected MPG represents the entire trip. A loaded-only MPG figure should not be applied to mixed loaded and empty operation without recognizing that assumption.

Use Matching Mileage and Fuel Records

To calculate an actual MPG value before using the table:

[
\text{Actual MPG} = \frac{\text{Miles traveled}}{\text{US gallons consumed}}
]

Match the distance and fuel consumption to the same vehicle and measurement interval. Odometer or trip records can provide mileage; fuel records must account for the fuel consumed during that interval, not simply purchases made during unrelated dates.

For a fill-to-fill measurement, record the odometer at a full tank, total the gallons added after that starting fill through the ending full fill, and divide the miles traveled by those gallons. Use a consistent fill level so changes in fuel remaining in the tank do not distort the comparison.

When combining several trips or reporting periods, divide total miles by total gallons. Do not take a simple average of the individual MPG figures.

Keep the measurement basis consistent when comparing results: vehicle, load, route, reporting interval, and treatment of fuel used while idling or operating auxiliary equipment. Load, road conditions, weather, and vehicle operation can affect actual fuel economy; converting the units does not adjust for those differences.