How to use MPG / Fuel Economy Calculator
The MPG calculator computes your vehicle's real-world fuel economy from fill-up data: miles driven and gallons used. It also converts between MPG (US), MPG (UK/imperial), L/100km and km/L so you can compare vehicles across international specifications, and lets you track multiple fill-ups to spot trends.
- Fill up your tank, reset the trip odometer.
- Drive normally, then fill up again — note miles driven and gallons added.
- Enter both values and click Calculate.
- Convert the result to any other fuel economy unit.
- Add multiple fill-ups to track average fuel economy over time.
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MPG formula and unit conversions
US MPG = miles ÷ gallons. To convert: L/100km = 235.215 ÷ US MPG; UK MPG = US MPG × 1.20095 (UK gallon is larger); km/L = US MPG × 0.425144. These conversions are important when comparing European (L/100km) cars with US (MPG) ratings or using imported vehicles with UK specifications.
| US MPG | UK MPG | L/100km | km/L |
|---|---|---|---|
| 20 | 24.0 | 11.8 | 8.5 |
| 30 | 36.0 | 7.8 | 12.8 |
| 40 | 48.0 | 5.9 | 17.0 |
| 50 | 60.0 | 4.7 | 21.3 |
| 60 | 72.1 | 3.9 | 25.5 |
Vehicle class fuel economy benchmarks (EPA)
Real-world MPG varies widely by vehicle class. Compact cars (Honda Civic, Toyota Corolla) achieve 30–38 MPG combined. Midsize sedans reach 28–35 MPG. SUVs range from 22–30 MPG. Full-size trucks: 15–22 MPG. Hybrids (Toyota Prius, Hyundai Ioniq): 45–60 MPG. Plug-in hybrids: 40–55 MPG on gas. Comparing your fill-up MPG to the EPA estimate tells you whether your driving style and conditions are average, better or worse.
Worked examples
320 miles on 12 gallons
Inputs: 320 ÷ 12
Result: ≈ 26.7 MPG
Convert 26.7 MPG to metric
Inputs: 235.21 ÷ 26.7
Result: ≈ 8.8 L/100km
European 6.5 L/100km to US MPG
Inputs: 235.21 ÷ 6.5
Result: ≈ 36.2 MPG
Typical combined MPG by vehicle class (EPA)
| Vehicle class | Typical combined MPG | Example |
|---|---|---|
| Compact car | 30–38 | Honda Civic, Corolla |
| Midsize sedan | 28–35 | Camry, Accord |
| SUV (crossover) | 22–30 | RAV4, CR-V |
| Full-size truck | 15–22 | F-150, Silverado |
| Hybrid | 45–60 | Prius, Ioniq |
Glossary
- MPGe
- Miles per gallon equivalent — used for electric vehicles, where 33.7 kWh equals one gallon of petrol.
- Combined MPG
- A weighted average of city (55%) and highway (45%) fuel economy used for EPA window stickers.
- Trip odometer
- A resettable odometer used to track miles for a specific fill-up interval.
- Fuel economy
- The distance a vehicle travels per unit of fuel; higher MPG = more fuel-efficient.
Related reading
Frequently Asked Questions
Why use MPG / Fuel Economy Calculator?
- Calculates real-world MPG from actual fill-up data rather than relying on EPA label estimates
- Converts between US MPG, UK MPG, L/100km and km/L in one step for international spec comparisons
- Tracks multiple consecutive fill-ups to reveal trends in fuel economy degradation or improvement
- Quantifies how far your measured efficiency deviates from the manufacturer's rated figure
Common use cases
- Measure whether a recent tune-up or tyre inflation improved your car's actual fuel economy
- Convert a European car's 6.5 L/100km specification to US MPG before comparing it to domestic models
- Track fill-up MPG across winter months to quantify cold-weather fuel economy losses
- Verify a used-car seller's claimed MPG by measuring your first two tanks after purchase
- Determine whether aggressive highway driving on a road trip reduced your average efficiency
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