MPG Calculator
Calculate your truck's actual miles per gallon and fuel cost per mile at various diesel prices.
Results
Visualization
How It Works
Knowing your actual MPG is the foundation of all trucking cost calculations. Most semi trucks get between 5.5 and 7.5 MPG, but this varies widely based on load weight, terrain, speed, tire condition, and driving habits. Tracking MPG at every fill-up helps you spot mechanical problems early and measure the impact of fuel-saving changes.
The Formula
Variables
- Miles Driven — Total miles traveled between fuel fill-ups
- Gallons Used — Total gallons of fuel consumed for those miles
Worked Example
You drove 500 miles and used 80 gallons of diesel. Your MPG is 500 / 80 = 6.25 MPG. At $3.85/gallon diesel, that means your fuel cost per mile is $3.85 / 6.25 = $0.616. Over a 10,000-mile month, you would spend about $6,160 on fuel at this efficiency.
Practical Tips
- Calculate MPG at every fill-up by using the trip odometer — reset it each time you fill up completely. Use a sharp, appropriate blade for each operation: rip blades (24-30 teeth) for cutting along the grain and crosscut blades (60-80 teeth) for cutting across the grain.
- Keep a log of your MPG over time to identify trends and seasonal changes in fuel efficiency. Apply this guidance to your specific circumstances, adjusting as needed for local conditions, material availability, and your particular requirements.
- Compare your MPG loaded vs empty to understand the true cost impact of heavy freight. Discuss this approach with experienced practitioners in your area, as local conditions and practices may affect how this advice applies to your situation.
- A sudden drop in MPG (0.5+ MPG) often indicates a maintenance issue like clogged air filters, low tire pressure, or injector problems. Set a weekly reminder to check all tire pressures including the spare, as even a slow leak of 1-2 PSI per week compounds into a safety and efficiency problem.
- Progressive shifting and steady throttle application can improve MPG by 0.5-1.0 over aggressive driving. Research current pricing and specifications from multiple sources before committing, as market conditions and product offerings change frequently.
Frequently Asked Questions
What is the average MPG for a semi truck?
The average Class 8 semi truck gets about 5.5-6.5 MPG. Newer trucks with aerodynamic fairings and fuel-efficient engines can achieve 7-8 MPG. The best-in-class trucks in ideal conditions have reached 10+ MPG in testing.
Why is my MPG lower than expected?
Common causes include heavy loads, mountainous terrain, cold weather, excessive idling, underinflated tires, high speeds (above 65 mph), worn engine components, and aggressive driving habits.
How much does speed affect truck MPG?
Significantly. Most trucks hit peak fuel efficiency at 55-62 mph. Every 1 mph increase above 65 mph typically costs about 0.1 MPG due to exponentially increasing wind resistance.
Does idle time affect MPG calculations?
Yes. If you idle for 8 hours burning 0.8 gallons/hour, that is 6.4 gallons consumed without any miles driven, which significantly lowers your calculated MPG. Consider tracking road MPG separately from overall MPG.
How do I calculate MPG accurately?
Fill your tank completely, reset the trip odometer, drive normally, then fill up completely again. Divide the miles driven by the gallons needed to refill. This fill-to-fill method is the most accurate way to measure real-world MPG.