City and Highway Blended MPG Calculator

What belongs in this calculation

Combine city and highway economy using distance shares rather than a simple arithmetic average — this page measures one relationship rather than diagnosing the entire vehicle.

Driving shares must total 100 percent — that condition defines when blended fuel economy is comparable with another result.

Input definitions that matter

City fuel economy. Measured or rated economy for city operation — for this measurement, match the fuel quantity to the same distance, fill method, and operating period.

Document Highway fuel economy as measured or rated economy for highway operation — this means you should match the fuel quantity to the same distance, fill method, and operating period.

For City driving share, use the quantity described as percentage of total distance driven in city conditions — in the vehicle record, keep the percentage basis explicit and do not mix a decimal fraction with a percent value.

This page does not attempt to translate a fuel reserve percentage into volume and approximate distance — the Fuel Reserve Range provides that calculation.

What the formula combines

In “blended MPG = 1 ÷ (city share ÷ city MPG + highway share ÷ highway MPG),” the printed units define how each term is interpreted.

No term beyond city fuel economy, highway fuel economy, and city driving share is introduced in “blended MPG = 1 ÷ (city share ÷ city MPG + highway share ÷ highway MPG).”

Blended fuel economy answers “Combine city and highway economy using distance shares rather than a simple arithmetic average.” The additional displays, Highway driving share and Gallons per 1,000 miles, are a different view of the same entered measurements.

Short trips and seasonal conditions may not match either reference cycle — when that condition changes, compare separate calculator runs instead of blending the inputs.

Because driving shares must total 100 percent, a disagreement between blended fuel economy and an outside reference should trigger a review of city fuel economy and city driving share.

Organizing the vehicle check

A repeatable city and highway blended mpg check begins with the instrument, operating interval, and vehicle state recorded together — this workflow must also account for the fact that driving shares must total 100 percent.

• Record City fuel economy as measured or rated economy for city operation — match the fuel quantity to the same distance, fill method, and operating period.
• Record Highway fuel economy as measured or rated economy for highway operation — match the fuel quantity to the same distance, fill method, and operating period.
• Record City driving share as percentage of total distance driven in city conditions — keep the percentage basis explicit and do not mix a decimal fraction with a percent value.
• Repeat the check only after accounting for this condition: driving shares must total 100 percent.

If your notes raise the question of how to estimate fuel consumed by an engine running without covering distance, move to the Engine Idle Fuel Consumption without changing this page's inputs.

Before acting on the number

The equation cannot determine whether city driving share was recorded with a calibrated instrument or under a repeatable operating condition — for city driving share, the page specifically expects percentage of total distance driven in city conditions.

Result and measurement questions