Gas Mileage Calculator
Free online gas mileage calculator. Calculate instantly with accurate results. No signup required.
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Your Fuel Efficiency
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MPG
Gas Mileage Calculator (MPG & L/100km)
Everything you need to know
About the Gas Mileage Calculator
Fuel costs are one of the largest ongoing expenses for vehicle owners. Our gas mileage calculator helps you track your vehicle's fuel efficiency in miles per gallon (MPG) or liters per 100 kilometers (L/100km), monitor trends over time, and identify ways to improve your fuel economy.
What you can calculate:
- Single tank MPG: Miles driven ÷ gallons used
- Trip fuel cost: Distance × fuel price per gallon
- Annual fuel cost: Miles per year ÷ MPG × price per gallon
- Metric efficiency: Liters per 100 km for international comparison
- MPG improvement impact: How much you save by improving MPG
How to Calculate Gas Mileage
Miles Per Gallon (MPG)
Formula: MPG = Miles Driven ÷ Gallons of Gas Used
Example: You drove 320 miles and used 11.5 gallons MPG = 320 ÷ 11.5 = 27.8 MPG
Liters Per 100 Kilometers (L/100km)
Formula: L/100km = (Liters Used ÷ Kilometers Driven) × 100
Example: You drove 500 km and used 42 liters L/100km = (42 ÷ 500) × 100 = 8.4 L/100km
Converting Between Systems
- MPG to L/100km: 235.215 ÷ MPG = L/100km
- L/100km to MPG: 235.215 ÷ L/100km = MPG
Example conversions:
- 25 MPG = 235.215 ÷ 25 = 9.4 L/100km
- 7 L/100km = 235.215 ÷ 7 = 33.6 MPG
Why Track Your Gas Mileage?
- Detect vehicle problems: Sudden drops in MPG can indicate engine issues, tire problems, or needed maintenance
- Budget accurately: Know your true fuel costs for trip planning
- Compare vehicles: Evaluate fuel efficiency when buying a new car
- Verify manufacturer claims: Real-world MPG often differs from EPA estimates
- Measure improvement: Track how driving habits affect efficiency
- Environmental impact: Higher MPG = lower carbon emissions
Factors That Affect Gas Mileage
| Factor | Impact | Solution |
|---|---|---|
| Aggressive driving | Reduces MPG by 15-30% | Accelerate smoothly, anticipate stops |
| Speed | Over 50 mph, MPG drops rapidly | Drive 55-65 mph on highways |
| Idling | 0 MPG while stopped | Turn off engine if stopped >30 seconds |
| Tire pressure | Underinflation reduces MPG by 0.2% per PSI | Check monthly, inflate to recommended PSI |
| Air conditioning | Reduces MPG by 5-25% | Use at highway speeds, open windows at low speeds |
| Roof racks | Reduce MPG by 2-8% | Remove when not in use |
| Extra weight | 100 lbs reduces MPG by 1% | Clean out unnecessary cargo |
| Cold weather | Reduces MPG by 15-30% | Park in garage, combine trips |
| Short trips | Engine doesn't reach optimal temp | Combine errands into one trip |
| Motor oil | Wrong viscosity reduces MPG | Use manufacturer-recommended oil |
Average MPG by Vehicle Type (2024)
| Vehicle Type | Average MPG | Annual Fuel Cost* |
|---|---|---|
| Compact car | 33 MPG | $1,455 |
| Midsize car | 29 MPG | $1,655 |
| Full-size car | 25 MPG | $1,920 |
| Compact SUV | 27 MPG | $1,778 |
| Midsize SUV | 23 MPG | $2,087 |
| Full-size SUV/Truck | 19 MPG | $2,526 |
| Hybrid car | 50 MPG | $960 |
| Electric (equivalent) | 120 MPGe | $400 |
*Based on 15,000 miles/year at $3.20/gallon
Calculating Trip Fuel Costs
Formula: Trip Cost = (Trip Distance ÷ MPG) × Price Per Gallon
Example: 500-mile road trip in a car getting 28 MPG, gas at $3.50/gallon Trip Cost = (500 ÷ 28) × 3.50 Trip Cost = 17.86 × 3.50 = $62.50
For a round trip (1,000 miles): Round Trip Cost = (1000 ÷ 28) × 3.50 = $125.00
Annual Fuel Cost Calculator
Formula: Annual Cost = (Annual Miles ÷ MPG) × Price Per Gallon
Example: 12,000 miles/year, 26 MPG, $3.40/gallon Annual Cost = (12,000 ÷ 26) × 3.40 Annual Cost = 461.54 × 3.40 = $1,569.23
If you improved to 30 MPG: Annual Cost = (12,000 ÷ 30) × 3.40 = $1,360.00 Annual savings: $209.23
Tips to Improve Your MPG
- Maintain steady speed: Use cruise control on highways
- Remove excess weight: Clean out your trunk
- Keep tires properly inflated: Check monthly
- Use the right oil: Check your owner's manual
- Replace air filters: Dirty filters reduce efficiency
- Plan routes: Avoid traffic and unnecessary stops
- Combine trips: Cold engines use more fuel
- Avoid roof cargo: Creates aerodynamic drag
- Drive sensibly: Rapid acceleration and braking waste fuel
- Maintain your vehicle: Regular tune-ups keep efficiency optimal
Frequently Asked Questions
What's considered good gas mileage?
- Excellent: 40+ MPG (hybrids, small cars)
- Good: 30-39 MPG (compact/midsize cars)
- Average: 20-29 MPG (SUVs, larger cars)
- Poor: Under 20 MPG (trucks, large SUVs)
Why does my car get worse MPG than the EPA estimate?
EPA estimates are conducted in controlled laboratory conditions. Real-world driving with traffic, hills, weather, and driving style typically results in 10-20% lower MPG.
How much can I save by improving my MPG by 5?
If you drive 15,000 miles/year at $3.50/gallon:
- At 20 MPG: $2,625/year
- At 25 MPG: $2,100/year
- Savings: $525/year
Is it better to measure MPG per tank or per trip?
Per tank gives you a good average over normal driving. Per trip helps you identify specific routes or driving styles that are more/less efficient.
What's the difference between city and highway MPG?
City driving involves frequent stops and starts, reducing MPG. Highway driving at steady speeds is more efficient. Your car's window sticker shows both estimates.