Gas Mileage Calculator
Calculate your MPG, fuel economy rating, and road trip fuel costs. Supports US (MPG) and metric units.
Calculator
Total miles since last fill-up
Gallons pumped at fill-up
Enter values above
Your fuel economy or trip cost will appear here.
On This Page
What Is Gas Mileage (MPG)?
Gas mileage, measured in miles per gallon (MPG), is the distance a vehicle can travel on one gallon of fuel. It is the primary metric used in the United States to evaluate fuel efficiency. A car with 30 MPG can travel 30 miles on a single gallon of gasoline.
Most countries outside the US use liters per 100 kilometers (L/100km) — where lower numbers mean better efficiency — or km/L (kilometers per liter), which works like MPG but in metric units. This calculator shows all three so you can compare easily.
The US Environmental Protection Agency (EPA) tests and rates every new vehicle sold in the US. However, real-world fuel economy is typically 10–20% lower than EPA estimates, due to driving conditions, speed, load, and weather.
How to Calculate Gas Mileage
MPG Formula
MPG = Miles Driven ÷ Gallons Used
Fill up your tank completely. Drive normally. When you fill up again, note the gallons pumped and the miles traveled since the last fill-up.
Fuel Cost Formula
Total Cost = (Miles ÷ MPG) × Gas Price per Gallon
First calculate how many gallons you'll need (miles ÷ MPG), then multiply by the gas price per gallon.
Unit Conversions
| Convert From | Convert To | Formula |
|---|---|---|
| MPG | L/100km | 235.215 ÷ MPG |
| L/100km | MPG | 235.215 ÷ L/100km |
| MPG | km/L | MPG × 0.425144 |
| km/L | MPG | km/L × 2.352 |
MPG Benchmarks by Vehicle Type
| Vehicle Type | City MPG | Highway MPG | L/100km (Hwy) |
|---|---|---|---|
| Compact / Sedan | 28–35 | 36–45 | 5.2–6.5 |
| Midsize SUV | 22–28 | 28–35 | 6.7–8.4 |
| Full-size Pickup Truck | 15–20 | 20–26 | 9.0–11.8 |
| Hybrid (non-plug-in) | 40–55 | 38–52 | 4.5–6.2 |
| Minivan | 18–22 | 24–30 | 7.8–9.8 |
| Sports Car | 16–22 | 24–32 | 7.4–9.8 |
Source: EPA fuel economy data, 2024 model year averages.
Worked Examples
Example 1: Calculate Your MPG
- • Miles driven since last fill-up: 300 miles
- • Gallons pumped at fill-up: 12 gallons
- • MPG = 300 ÷ 12 = 25.0 MPG (Average — typical of a midsize sedan)
- • Equivalent: 9.4 L/100km, 10.6 km/L
Example 2: Road Trip Fuel Cost
- • Trip distance: 1,200 miles (e.g., LA to Seattle)
- • Car's MPG: 28
- • Gas price: $3.50 per gallon
- • Gallons needed: 1,200 ÷ 28 = 42.9 gallons
- • Total fuel cost: 42.9 × $3.50 = $150.00
- • Cost per mile: $3.50 ÷ 28 = $0.125 per mile
Example 3: European Metric Mode
- • Distance driven: 500 km
- • Fuel used: 45 liters
- • L/100km = (45 ÷ 500) × 100 = 9.0 L/100km (Average)
- • Equivalent: 26.1 MPG (US)
Tips to Improve Your Fuel Economy
Check Tire Pressure
Under-inflated tires increase rolling resistance and reduce MPG by up to 3%. Check monthly — especially in cold weather.
Drive Smoothly
Avoid rapid acceleration and hard braking. Smooth throttle inputs can improve fuel economy by 10–40% in stop-and-go traffic.
Reduce Highway Speed
Every 5 mph over 50 mph costs about 7–14% more fuel. Dropping from 75 to 65 mph on a road trip can save a noticeable amount.
Remove Extra Weight
An extra 100 lbs reduces MPG by about 1%. Empty your trunk of unnecessary items, especially for city driving.
Maintain Your Engine
Replacing a dirty air filter can improve MPG by up to 10%. Fresh spark plugs, clean fuel injectors, and fresh oil all help.
Use Cruise Control
Maintaining a constant speed on the highway eliminates the small speed variations that waste fuel. Cruise control typically improves highway MPG by 7–14%.
Frequently Asked Questions
About This Calculator
Free gas mileage calculator. Instantly calculate your MPG, fuel economy rating, and road trip fuel costs. Supports US (MPG) and metric units (L/100km).
Frequently Asked Questions
How do I calculate MPG?
MPG (miles per gallon) = Miles Driven ÷ Gallons Used. For example, if you drove 300 miles and used 12 gallons, your fuel economy is 300 ÷ 12 = 25 MPG.
What is a good MPG for a car?
For passenger cars, 25–30 MPG is average, 30–40 MPG is good, and 40+ MPG is excellent (typical of hybrids). SUVs average 20–28 MPG. Trucks average 15–22 MPG.
How do I calculate fuel cost for a road trip?
Use the Fuel Cost tab: enter your trip distance, your car's MPG, and the current gas price per gallon. The calculator computes total gallons needed and total cost.
What is L/100km and how does it compare to MPG?
L/100km is the fuel economy standard used in most countries outside the US. Lower is better. To convert: L/100km = 235.215 ÷ MPG. So 28 MPG ≈ 8.4 L/100km.
How can I improve my gas mileage?
Maintain proper tire pressure, drive smoothly, reduce highway speed, remove extra cargo weight, and keep up with engine maintenance (air filters, spark plugs).
Mike is a software engineer with a background in applied mathematics. He develops and maintains SuperCalc's engineering, conversion, and math utility calculators.
- M.S. in Applied Mathematics, MIT
- Former quantitative developer
- 6 years building computational tools