Gas Mileage Calculator — Track MPG & Estimate Trip Fuel Costs
Calculate your car's actual fuel efficiency in MPG or L/100km. Compare real-world economy to rated MPG, estimate trip costs, and find out if your car is underperforming.
Your car's rated MPG from the manufacturer is measured under controlled lab conditions. Real-world fuel economy is usually 10–20% lower, depending on how you drive, road conditions, AC usage, and how loaded the car is. Tracking your actual mileage takes 60 seconds at each fill-up and tells you whether your car is running well or burning more than it should.
Use CalcHub's gas mileage calculator to calculate MPG, compare against the EPA rating, and estimate what a trip will cost you.
Calculating MPG
MPG = miles driven ÷ gallons used- Fill your tank completely. Note the odometer reading.
- Drive normally until next fill-up.
- At the next fill-up: note the odometer reading and how many gallons it takes to fill the tank completely again.
- Miles driven = new odometer − old odometer
- MPG = miles driven ÷ gallons added at second fill-up
L/100km (Metric Fuel Economy)
Indian and European cars use liters per 100 kilometers — the lower the number, the more efficient.
L/100km = (liters used ÷ km driven) × 100L/100km = 235.215 ÷ MPG| MPG | L/100km | Efficiency Category |
|---|---|---|
| 15 | 15.7 | Poor (large truck/SUV) |
| 20 | 11.8 | Below average |
| 25 | 9.4 | Average (sedan) |
| 30 | 7.8 | Good |
| 35 | 6.7 | Very good |
| 40 | 5.9 | Excellent (hybrid) |
| 50 | 4.7 | Hybrid/EV equivalent |
| 60 | 3.9 | Top hybrid |
Trip Cost Estimator
fuel cost = (trip distance ÷ MPG) × price per gallonOr metric:
fuel cost = (trip distance in km × L/100km ÷ 100) × price per liter- 400 ÷ 28 = 14.3 gallons
- 14.3 × $3.50 = $50.00
- 230 × 14 ÷ 100 = 32.2 liters
- 32.2 × ₹103 = ₹3,317
What's Hurting Your Fuel Economy?
| Factor | Impact on MPG |
|---|---|
| AC running | −5 to −15% |
| Cold engine (short trips) | −20 to −40% |
| Under-inflated tires | −0.5% per PSI under |
| Roof rack with cargo | −5 to −25% |
| Highway vs. city | +30 to +50% highway |
| Every 5 mph over 50 mph | −7 to −14% efficiency drop |
| Aggressive acceleration | −15 to −40% |
| Carrying heavy cargo | Variable, ~1–2% per 100 lbs |
Break-Even: Is the Hybrid Worth It?
If you're comparing a regular car to a hybrid:
Break-even miles = (price premium) ÷ ((fuel savings per mile))
fuel savings per mile = (1/MPG_regular − 1/MPG_hybrid) × gas price- Fuel cost per km, regular: ₹100/15 = ₹6.67/km
- Fuel cost per km, hybrid: ₹100/25 = ₹4.00/km
- Savings per km: ₹2.67
- Break-even: 3,00,000 ÷ 2.67 = ~1,12,360 km (about 7–8 years for most drivers)
Why is my actual MPG lower than the sticker?
EPA test cycles don't replicate real driving — they don't simulate stop-and-go traffic, cold starts, highway speeds above 60 mph, AC use, or cargo weight. Real-world MPG is typically 10–20% below the rated figure.
How often should I track my fuel economy?
Fill-up to fill-up is most accurate. After 3–5 fill-ups you'll have a reliable average. A sudden 15%+ drop in MPG is worth investigating — it often signals a maintenance issue (dirty air filter, worn spark plugs, tire pressure drop).
Does premium fuel improve MPG in a regular car?
No. Premium fuel's higher octane rating only benefits engines that require it (high-compression, turbocharged). Using premium in a regular engine wastes money with no efficiency gain.