HIFreeTools
ENES

Fuel Efficiency Calculator

Calculate your vehicle's fuel efficiency in miles per gallon (MPG) or liters per 100 kilometers (L/100km) by entering your trip distance and fuel consumed. You can also convert between MPG and L/100km or estimate fuel cost per mile.

Enter values above to calculate fuel efficiency.

Quick Reference

MPG = distance (mi) ÷ fuel (gal)

L/100km = (fuel (L) ÷ distance (km)) × 100

Convert: L/100km = 235.214 ÷ MPG

Cost/mile = gas price ($) ÷ MPG

Quick answer

Fuel efficiency measures how far a vehicle travels per unit of fuel. In the US, it is expressed as miles per gallon (MPG) — divide distance in miles by gallons used. In most other countries, fuel consumption is expressed as liters per 100 kilometers (L/100km) — divide liters used by kilometers driven, then multiply by 100. A higher MPG means better efficiency, while a lower L/100km also means better efficiency. To convert MPG to L/100km, divide 235.214 by the MPG value.

Formula & method

MPG = distance (miles) ÷ fuel used (gallons)
  • MPG — Miles per gallon (fuel economy)
  • distance — Total distance driven in miles
  • fuel used — Total fuel consumed in gallons

US standard fuel economy. Higher is more efficient.

L/100km = (fuel used in liters ÷ distance in km) × 100
  • L/100km — Liters of fuel consumed per 100 kilometers
  • fuel used — Total fuel consumed in liters
  • distance — Total distance driven in kilometers

Metric fuel consumption standard. Lower is more efficient.

L/100km = 235.214 ÷ MPG
  • 235.214 — Conversion constant (based on US gallon and mile definitions)
  • MPG — Miles per gallon value to convert

Conversion formula between MPG and L/100km.

Cost per mile = gas price ($/gal) ÷ MPG
  • Cost per mile — Fuel cost in dollars for each mile driven
  • gas price — Price per gallon of gasoline in dollars
  • MPG — Vehicle fuel economy in miles per gallon

Calculates how much fuel costs per mile driven.

Examples

Example 1: Calculate MPG for a Road Trip
Input
Distance: 350 miles, Fuel used: 12 gallons
Result
29.17 MPG
Why
Divide 350 miles by 12 gallons: 350 ÷ 12 = 29.17 MPG. This is slightly above the average new car rating of about 28 MPG, indicating reasonably good highway efficiency.
Example 2: Calculate L/100km for a European Trip
Input
Distance: 500 km, Fuel used: 45 liters
Result
9.0 L/100km
Why
Divide liters by km, then multiply by 100: (45 ÷ 500) × 100 = 9.0 L/100km. This is a moderate consumption figure for a petrol car; efficient vehicles typically achieve 5–7 L/100km on highways.
Example 3: Convert MPG to L/100km
Input
Fuel economy: 30 MPG
Result
7.84 L/100km
Why
Use the conversion formula: 235.214 ÷ 30 = 7.84 L/100km. This confirms that 30 MPG is equivalent to consuming 7.84 liters for every 100 kilometers of driving.
Example 4: Calculate Fuel Cost per Mile
Input
MPG: 28, Gas price: $3.50 per gallon
Result
$0.125 per mile
Why
Divide gas price by MPG: 3.50 ÷ 28 = $0.125 per mile. Over a 10,000-mile year, this adds up to export const batch4Tools: ToolContent[] = ,250 in fuel costs — useful for comparing two vehicles before purchase.

Frequently asked questions

What is a good MPG for a car?

For a new car in the US, 30 MPG or higher is generally considered good. Hybrid vehicles often achieve 45–55 MPG, while electric vehicles are rated in MPGe (miles per gallon equivalent). City driving typically yields lower MPG than highway driving because of stop-and-go traffic.

What is a good L/100km rating?

For a petrol/gasoline car, under 7 L/100km is considered efficient, and under 5 L/100km is excellent. Diesel cars typically achieve 4–6 L/100km. Hybrid and electric vehicles can reach 3–4 L/100km equivalent. Higher-performance or heavier vehicles may use 10–15 L/100km.

Why does my actual MPG differ from the EPA estimate?

EPA estimates are measured under controlled test conditions. Real-world MPG varies based on driving style (aggressive acceleration reduces MPG by 15–30%), speed (aerodynamic drag increases sharply above 60 mph), climate (cold weather thickens engine oil and reduces battery efficiency in hybrids), cargo weight, and road grade. Measuring your own MPG at the pump gives the most accurate figure for your habits.

How do I measure my fuel efficiency at the pump?

Fill your tank to full, reset your trip odometer to zero, and drive normally. Next time you fill up, note the miles driven (odometer) and the gallons added to refill. Divide miles by gallons for your MPG. For L/100km, note kilometers driven and liters pumped, then compute (liters ÷ km) × 100.

Does tire pressure affect fuel efficiency?

Yes. Under-inflated tires increase rolling resistance and can reduce fuel economy by 0.2–0.5% for every 1 PSI drop below the recommended pressure. Keeping tires at the manufacturer-recommended pressure (found on the door jamb sticker) is one of the simplest ways to maintain peak efficiency and also improves tire longevity.

What is the difference between fuel economy and fuel consumption?

Fuel economy expresses how far you go per unit of fuel (MPG or km/L) — higher numbers are better. Fuel consumption expresses how much fuel you use per unit of distance (L/100km or gallons/100mi) — lower numbers are better. The US uses fuel economy (MPG); most of Europe and Asia use fuel consumption (L/100km). Both measure the same underlying efficiency but from opposite directions.

Sources & references

External references open in a new tab. We are independent and not affiliated with these organizations.

  • ✓ Free to use
  • ✓ No sign-up required
  • ✓ Runs entirely in your browser — nothing is uploaded.
  • ✓ Formula and method shown above
Last updated: How we calculateReport a correctionDisclaimer

Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.

Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.

Related tools

Embed this tool on your site

Free to embed, no sign-up. Paste this code where you want the fuel efficiency calculator to appear: