Gallons Per 100 Miles Calculator
Calculate fuel consumption per 100 miles from MPG ratings or actual trip data. Understand real fuel efficiency and compare vehicles accurately.
Fuel Consumption Input
Calculation Method
Miles per gallon rating from EPA sticker or trip computer
Fuel Efficiency Results
Enter your fuel data to calculate gallons per 100 miles
Compare efficiency and fuel costs
Fuel Efficiency Gauge
Efficiency Scale
Gallons Per 100 Miles
Most people talk about fuel efficiency in terms of "miles per gallon" or MPG. While MPG is useful, it can be misleading when comparing vehicles or understanding real fuel costs. Gallons per 100 miles (G/100mi) gives you a clearer picture of fuel consumption.
Instead of asking "How far can I go on one gallon?", G/100mi asks "How much fuel do I actually burn to travel 100 miles?" Lower numbers mean better efficiency, and small differences become much clearer.
How to Calculate G/100mi
There are two main ways to calculate gallons per 100 miles:
Method 1: From MPG Rating
Gallons/100mi = 100 ÷ MPG
Example: 25 MPG = 100 ÷ 25 = 4.0 gallons per 100 miles
Method 2: From Actual Trip Data
Gallons/100mi = (Fuel Used ÷ Distance) × 100
Example: 15 gallons over 300 miles = (15 ÷ 300) × 100 = 5.0 gallons per 100 miles
Efficiency Ratings Explained
Vehicle Efficiency Comparison
| Vehicle Type | MPG | G/100mi | Efficiency |
|---|---|---|---|
| Hybrid Car | 45 | 2.2 | Excellent |
| Sedan | 30 | 3.3 | Good |
| SUV | 22 | 4.5 | Average |
| Pickup Truck | 18 | 5.6 | Average |
Trip Calculation Example
| Distance Driven | 450 miles |
| Fuel Used | 22.5 gallons |
| Calculation | (22.5 ÷ 450) × 100 |
| G/100mi Result | 5.0 |
Practical Applications
Gallons per 100 miles is invaluable for:
- Vehicle Comparisons: See real fuel consumption differences between cars
- Trip Planning: Calculate fuel needs for road trips and long drives
- Fleet Management: Track and compare fuel efficiency across vehicles
- Cost Analysis: Understand fuel expenses for budgeting and planning
- Environmental Impact: Compare carbon footprints between vehicles
Factors Affecting G/100mi
Several factors can change your gallons per 100 miles:
- Driving Style: Aggressive driving increases consumption by 10-20%
- Vehicle Load: Extra weight reduces efficiency
- Terrain: Hills and mountains increase fuel use
- Weather: Cold weather and strong winds affect aerodynamics
- Maintenance: Poor tire pressure and maintenance hurt efficiency
Whether you're comparing vehicles, planning a road trip, or managing a fleet, understanding gallons per 100 miles gives you a clearer picture of real fuel consumption than MPG alone can provide.