Calculate miles per gallon, fuel cost per mile, trip fuel consumption, and convert MPG to L/100km. Four fuel economy modes — one free tool covering every fuel calculation you need.
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All fuel economy formulas and reference data on this page are sourced from authoritative government and industry standards:
Miles per gallon (MPG) is the standard U.S. measure of fuel economy — how far your vehicle travels on one gallon of gasoline or diesel. The calculation is simple: divide the miles you drove by the gallons you used to refill your tank. The fill-to-fill method is the most accurate because it removes any partial-tank measurement error.
MPG = Miles Driven / Gallons Used to Refill
Example: 385 miles driven, 13.75 gallons = 385 / 13.75 = 28.0 MPG
Fuel cost per mile = Gas price per gallon / MPG
Example: $3.60 / 28 MPG = $0.129 per mile (12.9 cents/mile)
Knowing your fuel cost helps you budget road trips, compare vehicles, and track spending. The fuel cost formula multiplies distance by the cost per mile. For trip planning, the gas cost calculator above lets you enter any distance, your vehicle's MPG, and the current gas price to get the exact fuel cost — including round trips and carpooling splits.
Trip fuel cost = (Distance / MPG) x Gas price per gallon
Monthly fuel cost = (Monthly miles / MPG) x Gas price
Annual fuel cost = (Annual miles / MPG) x Gas price
Cost per mile = Gas price / MPG
The fuel consumption calculator answers: how many gallons (or liters) will I need for this trip? This is essential before a long drive — you can check whether you have enough range on your current tank, or know exactly how much you'll spend at the next fill-up. For metric users, the L/100km consumption mode calculates liters needed for any kilometer distance.
Gallons needed = Trip distance (miles) / MPG
Liters needed = Trip distance (km) / 100 x L/100km rating
Example: 500 miles at 28 MPG = 500 / 28 = 17.86 gallons
Example: 800km at 9.0 L/100km = (800/100) x 9.0 = 72 liters
The United States uses MPG while Canada, the European Union, and Australia measure fuel efficiency in liters per 100 kilometers (L/100km). The conversion uses the constant 235.21, derived from the exact conversion factors between U.S. gallons, liters, miles, and kilometers. A lower L/100km means better fuel efficiency — the opposite direction from MPG where higher is better.
L/100km = 235.21 / MPG
MPG = 235.21 / L/100km
28 MPG = 235.21 / 28 = 8.40 L/100km
35 MPG = 235.21 / 35 = 6.72 L/100km
9.0 L/100km = 235.21 / 9.0 = 26.1 MPG
Fuel economy expectations vary significantly by vehicle class. Comparing a pickup truck's MPG to a compact car's is misleading — what matters is how your vehicle performs within its own class. The EPA rates new vehicles using a standardized test cycle, but real-world MPG is typically 10-20% lower due to driving style, weather, and vehicle condition.
| Vehicle Type | Good MPG | Excellent MPG | Avg. Annual Fuel Cost* |
|---|---|---|---|
| Compact car | 30–33 | 35+ | $1,300–$1,580 |
| Midsize sedan | 27–30 | 33+ | $1,580–$1,750 |
| Midsize SUV | 23–26 | 28+ | $1,800–$2,200 |
| Compact SUV | 27–30 | 32+ | $1,450–$1,750 |
| Full-size pickup (V8) | 16–19 | 21+ | $2,400–$3,200 |
| Minivan | 21–24 | 26+ | $1,980–$2,250 |
| Hybrid sedan | 44–50 | 52+ | $850–$1,050 |
| Plug-in hybrid | 50–65 MPGe | 70+ MPGe | $600–$900 |
*Based on 13,500 annual miles and $3.60/gallon average.
The EPA conducts fuel economy tests under laboratory conditions designed to represent average driving. Real-world driving introduces many factors that reduce fuel economy. Cold starts — driving before the engine reaches operating temperature — increase fuel consumption by 10-40% for short trips. Highway driving above 65 mph increases aerodynamic drag exponentially: driving at 75 mph uses approximately 20% more fuel than 60 mph. Air conditioning adds 5-25% fuel load in hot weather.
Improving fuel economy saves real money. At 13,500 annual miles and $3.60 gas, going from 25 MPG to 30 MPG saves $343 per year. Going from 20 MPG to 30 MPG saves $810 per year. The most impactful changes are driving behavior, not mechanical — smooth acceleration and braking alone can improve city MPG by 15-30%.
MPG savings rule of thumb: Every 5 MPG improvement saves approximately $150-$200 per year at average US driving levels and $3.60 gas. A vehicle upgrade from 20 MPG to 40 MPG saves $1,620/year — easily justifying a hybrid premium within 3-4 years of ownership.
For daily commuters, the fuel cost calculator in Mode 2 above handles monthly and annual calculations. Enter your one-way commute distance, set trips to "30 (daily commute/month)" or "365 (annual)", and your MPG and gas price. This gives you the exact annual cost of your commute — a number that often surprises people and quantifies the value of moving closer to work or shifting to remote days.
Planning a road trip requires knowing how many fuel stops you'll need and how much to budget. Use Mode 3 (Consumption) to enter your total trip distance and your vehicle's MPG. The calculator returns gallons needed, number of fill-ups at a standard 12-gallon fill (for planning purposes), and total fuel cost at your entered gas price. This is especially useful when driving through areas where gas prices differ significantly.