How Actual vs Rated MPG Comparator Works?
This tool works by subtracting the window sticker miles per gallon (MPG) from your measured MPG and dividing by the sticker MPG. The result is the percentage gap between real and rated fuel economy.
Find the rated MPG
Use the combined EPA rating from the window sticker or fueleconomy.gov, for example 32 MPG.
Measure your actual MPG
Use the full-to-full method over several tanks, for example 27.5 MPG.
Enter both values
Type the rated and measured MPG.
Read the variance
A negative percentage means real MPG falls below the rating.
Actual vs Rated MPG Comparator Formula
The formula is Variance % = ((Measured MPG − Rated MPG) ÷ Rated MPG) × 100.
Variance % = ((Measured − Rated) ÷ Rated) × 100Formula variables
- Measured MPG
- Real-world fuel economy from your own fill-ups.
- Rated MPG
- Official EPA combined rating.
Worked example
- Official Window Sticker MPG: 32 MPG
- Real Measured MPG: 27.5 MPG
- Gap: 27.5 − 32 = −4.5 MPG.
- Variance: (−4.5 ÷ 32) × 100 = −14.1%.
Result: -14.1% (% variance)
A variance of −5% to −15% is common in real driving. A variance worse than −20% points to aggressive driving, short trips, heavy loads, or a mechanical problem.
Actual vs Rated MPG Comparator Conversion Table
The table shows the percentage variance for 4 rated MPG values and 3 measured MPG values.
Rows: Official Window Sticker MPG (MPG). Columns: Real Measured MPG (MPG). Cells: % variance.
| MPG | 22 MPG | 27.5 MPG | 35 MPG |
|---|---|---|---|
| 25 MPG | -12.0% | 10.0% | 40.0% |
| 32 MPG | -31.3% | -14.1% | 9.4% |
| 40 MPG | -45.0% | -31.3% | -12.5% |
| 50 MPG | -56.0% | -45.0% | -30.0% |
A 25 MPG rated car measuring 35 MPG beats its rating by 40.0%, while a 50 MPG rated hybrid measuring 22 MPG falls 56.0% short.
What is Actual vs Rated MPG Comparator?
The Actual vs Rated MPG Comparator is a tool that compares your real fuel economy with the official rating. The tool shows whether a vehicle performs as advertised.
The US Environmental Protection Agency (EPA) rates fuel economy in lab tests that model typical driving. Real results depend on speed, climate, terrain, and driving style.
A large negative variance is a signal to check tires, air filters, brakes, and driving habits.
What are the uses of Actual vs Rated MPG Comparator?
There are 4 main uses of the Actual vs Rated MPG Comparator: diagnosing poor fuel economy, judging driving style, comparing vehicles fairly, and checking used car condition.
Diagnosing poor fuel economy
Owners spot a −20% or worse gap that points to a fault.
Judging driving style
Drivers see how speed and acceleration change the gap.
Comparing vehicles fairly
Reviewers report real MPG next to the rating.
Checking used car condition
Buyers test whether a used car still meets its rating.
Need every metric in one place? Open the main MPG Cost Calculator or browse all 101 fuel calculators.