Gas Mileage Calculator
Calculate your MPG, cost per mile, trip fuel costs, and annual fuel budget. Compare against EPA averages for all vehicle classes.
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Hybrids average 47 MPG; plug-in hybrids can reach 60+ MPG equivalent. A 5 MPG improvement on 15,000 miles/year at $3.50/gal saves about $350 annually. Real-world MPG often differs from EPA due to driving conditions and habits.
Ready to run the numbers?
Why: Tracking fuel economy helps you budget, spot maintenance issues, and compare vehicles. Cost per mile is the true measure of driving expense.
How: MPG = Miles ÷ Gallons. For trip cost: (Distance ÷ MPG) × Gas Price. EPA provides standardized estimates for comparison.
Run the calculator when you are ready.
⛽ Sample Examples — Click to Load
Calculator Mode
Fill-Up Data
Annual Fuel Cost by Vehicle Class
How MPG Affects Annual Fuel Cost
Calculation Breakdown
For educational purposes only — not financial advice. Consult a qualified advisor before making decisions.
💡 Money Facts
EPA combined MPG is a weighted average of 55% city and 45% highway driving.
At $3.50/gal, improving from 20 to 30 MPG saves about $580 per 15,000 miles.
L/100km = 235.215 ÷ MPG. A 30 MPG car uses about 7.8 L/100km.
Plug-in hybrids can achieve 60+ MPG equivalent when charged regularly.
📋 Key Takeaways
- • MPG = Miles Driven ÷ Gallons Used — the fundamental fuel economy formula from the EPA
- • The average US car gets 27.5 MPG (combined city/highway, 2024 model year average per EPA)
- • The average American drives 13,500 miles/year (FHWA data), spending ~$1,600/year on gas
- • Improving from 20 to 30 MPG saves $730/year at $3.25/gallon over 13,500 miles
💡 Did You Know?
📖 How Gas Mileage Calculation Works
Gas mileage (MPG) measures how far your vehicle travels per gallon of fuel. The EPA formula is simple: divide miles driven by gallons used. From there, you can derive cost per mile, trip costs, and annual fuel budgets. The calculator supports three modes: calculate MPG from a fill-up, estimate trip fuel cost using known MPG, or project annual fuel spending.
MPG from Fill-Up
Record odometer at fill-up, drive until next fill-up, then divide miles driven by gallons added. For accuracy, average over 3–5 fill-ups.
Cost per Mile
Cost per Mile = Gas Price ÷ MPG. At $3.25/gal and 30 MPG, each mile costs about $0.108. Useful for comparing vehicles and trip planning.
Trip & Annual Cost
Trip Cost = (Distance ÷ MPG) × Gas Price. Annual Cost = (Annual Miles ÷ MPG) × Gas Price. FHWA reports average US driver logs 13,500 miles/year.
🎯 Expert Tips
Drive Smoothly
Aggressive driving (speeding, rapid acceleration, hard braking) lowers MPG by 15-30% at highway speeds. Use cruise control when possible.
Reduce Weight & Drag
Remove roof racks when not in use (5-25% MPG penalty at highway speeds). Every 100 lbs of cargo reduces MPG by about 1-2%.
Maintain Your Vehicle
Replace air filters, use recommended motor oil, and keep engine tuned. A serious maintenance problem can reduce MPG by up to 40%.
Plan Your Trips
Combine errands to avoid multiple cold starts. A warm engine is 12% more fuel-efficient. Avoid idling — it gets 0 MPG.
⚖️ This Calculator vs. Alternatives
| Method | Pros | Cons |
|---|---|---|
| This Calculator | MPG + trip + annual modes, EPA vehicle comparison, cost per mile, no signup | Requires fill-up data or known MPG |
| EPA FuelEconomy.gov | Official EPA data, vehicle lookup by make/model | Sticker estimates only; no personal fill-up tracking |
| Fuel Tracking Apps | Automatic odometer sync, history over time | Requires app install; some require subscription |
| Manual Spreadsheet | Full control, customizable | Time to build; prone to formula errors |
❓ Frequently Asked Questions
How do I calculate my gas mileage?
Fill your tank completely and record the odometer. Drive normally until you need to refuel. Fill up again and record the gallons needed and new odometer reading. Divide miles driven by gallons used: MPG = Miles ÷ Gallons. For accuracy, track over multiple fill-ups.
What is a good MPG?
The US new car fleet average is about 27.5 MPG. Above 30 MPG is good, above 40 is very good, and hybrids/PHEVs can exceed 50-60 MPG. For trucks and SUVs, 22-25 MPG is considered good. Always compare within your vehicle class.
Why is my actual MPG lower than the EPA rating?
Real-world driving differs from EPA lab tests. Short trips, cold weather, aggressive driving, using A/C, hilly terrain, and city driving all reduce MPG. The EPA estimates are useful for comparing vehicles but expect 10-20% lower in practice.
How much does speed affect fuel economy?
Fuel economy drops significantly above 50 mph. Each 5 mph over 50 is like paying an extra $0.18/gallon. At 75 mph, you use about 25% more fuel than at 55 mph due to exponentially increasing aerodynamic drag.
What is L/100km and how does it compare to MPG?
Liters per 100 kilometers is the metric fuel economy standard used outside the US. Lower is better (opposite of MPG). Convert: L/100km = 235.215 ÷ MPG. For example, 30 MPG ≈ 7.8 L/100km.
Should I use premium or regular gas?
Use the octane level recommended in your owner's manual. Using premium in a car designed for regular provides no benefit and wastes money. Using regular in a car that requires premium can cause engine knock and damage.
How often should I check my tire pressure?
Check tire pressure at least monthly. Tires lose 1-2 PSI per month naturally. Proper inflation improves MPG by up to 3% and extends tire life. Check when tires are cold (before driving).
Does using A/C hurt fuel economy?
Yes. A/C can reduce fuel economy by 5-25% depending on outside temperature and vehicle. At highway speeds, open windows create drag—A/C may be more efficient. At low speeds, opening windows is often better.
📊 Fuel Economy by the Numbers
📚 Official Sources
⚠️ Disclaimer: Gas mileage varies based on driving conditions, vehicle maintenance, weather, terrain, and driving habits. EPA estimates are for comparison purposes. Actual results may differ. Gas prices fluctuate daily — check AAA or GasBuddy for current local prices.
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