Free gas mileage calculator
Enter miles driven and gallons used — this gas mileage calculator returns your mpg plus L/100km and km/L equivalents for international comparison, updated live, as you type.
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Actual fuel consumption depends on driving style, terrain, and vehicle condition. EPA ratings are for comparison only.
Results are estimates. Consult a professional.
How the gas mileage calculator works
Gas mileage — formally fuel economy — measures how far a vehicle travels per unit of fuel consumed. In the United States the standard unit is miles per gallon (mpg). This calculator computes your actual mpg from real fill-up data using the fill-up method, then converts the result to international equivalents for comparison.
The fill-up method is the gold standard for real-world mpg measurement: fill your tank to the brim, record the odometer, drive normally, then fill to the brim again. Divide the miles driven between fill-ups by the gallons pumped in the second fill. This eliminates errors from partial fills and gives an accurate picture of your actual fuel efficiency under your driving conditions.
EPA fueleconomy.gov — tips for measuring real-world fuel economyWorked example: fill-up method on a daily commuter
Setup: Fill tank on Monday at 42,105 miles odometer. Drive through the week. Fill again on Friday at 42,492 miles odometer. Second fill takes 12.4 gallons. Miles driven = 42,492 − 42,105 = 387 miles.
Fuel economy by vehicle type: mpg, L/100 km, km/L
The table below shows typical EPA combined mpg ratings for common US vehicle categories in 2024, along with metric equivalents. Use the mpg column to benchmark your fill-up result against vehicles in the same class.
| Vehicle Type | Typical mpg (EPA) | L/100 km | km/L |
|---|---|---|---|
| Compact car | 32–38 mpg | 6.2–7.4 | 13.6–16.2 |
| Mid-size sedan | 28–34 mpg | 6.9–8.4 | 11.9–14.5 |
| Full-size SUV | 18–24 mpg | 9.8–13.1 | 7.7–10.2 |
| Half-ton pickup truck | 16–22 mpg | 10.7–14.7 | 6.8–9.4 |
| Non-plug-in hybrid | 40–55 mpg | 4.3–5.9 | 17.0–23.4 |
| Electric vehicle (MPGe) | 90–130 MPGe | 1.8–2.6 | 38.3–55.3 |
Source: EPA fueleconomy.gov 2024 model year data; ranges represent most common configurations.
Tips for accurate mpg measurement and improvement
Accurately measuring mpg requires consistency. One fill-up cycle can be skewed by a non-brimming fill or a hill-heavy route. Averaging three to five fill-up cycles gives a reliable baseline.
- Always fill to the first click — both times — The fill-up method only works when the starting and ending fuel levels are identical. Stop at the first automatic click both times; overfilling past the click introduces measurement error.
- Track multiple fill-ups before drawing conclusions — A single fill-up result can be skewed by an unusually hilly route, cold weather, or heavy cargo. Calculate mpg over three or more consecutive fill-ups and average the results for reliability.
- Compare highway and city fill-ups separately — If you take a long road trip, keep that fill-up separate. Mixing highway and city driving obscures which conditions are hurting your mpg and makes troubleshooting harder.
- EPA combined mpg is 15–20% optimistic for most drivers — The EPA test cycle uses 48 mph as an average highway speed and doesn't fully simulate AC loads, cold-climate starts, or aggressive acceleration. Expect real-world results to land in the 80–90% range of the sticker.
- Low mpg triggers worth checking — A sudden 10%+ drop in mpg often signals an actionable problem: under-inflated tires (check PSI), a dirty air filter (replace every 15,000–30,000 miles), a failing O2 sensor, or a stuck brake caliper. Run diagnostics before assuming it's just driving style.
Accuracy and limitations
The fill-up method is accurate to within 1–2% under consistent conditions, but several factors introduce variability. Fuel pumps at different stations have different nozzle pressures, which affects how full the tank fills to the first click. Temperature changes the density of gasoline slightly — fuel is denser and slightly more energy-rich in cold weather, which can marginally improve mpg readings in winter.
Electric vehicle efficiency is measured in miles per gallon equivalent (MPGe) or miles per kWh (mi/kWh), not mpg. The EPA defines 1 gallon of gasoline as containing 33.7 kWh of energy for MPGe calculations. This calculator is designed for gasoline vehicles; for EVs, use a dedicated kWh/mile calculator. Plug-in hybrids (PHEVs) require separate accounting for electric and gasoline miles to yield meaningful fuel cost numbers.
Gas mileage terms defined
About this gas mileage calculator
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