Diesel Trip Cost Calculator: 2026 Fuel Cost for Any Route

This calculator uses the current EIA national average diesel price ($5.59/gal, updated April 29, 2026) as the default. You can override with any state's price or enter a custom price from your local pump. The fuel cost output is mathematically exact given the inputs: gallons = miles / mpg; cost = gallons x price/gal. Real-world variance comes from your actual mpg (which changes with load, terrain, speed, and headwind) and actual local diesel prices.

Class 8 semi-trucks average 6-8 mpg on flat interstate at 65 mph with a loaded trailer. Use 7 mpg as the baseline. For hilly terrain or heavy loads (over 70,000 lbs GVW), use 5-6 mpg. For a partial load or empty run, use 8-10 mpg. These are tested EPA averages from the DOE Smartway and ATA Trucking Efficiency programs. Better aerodynamics (side fairings, trailer skirts, automatic tire inflation) can improve efficiency by 5-10%.

For fleet-level calculations, use the Fleet Fuel Calculator at /fleet-fuel-calculator. It handles cost per mile, monthly fuel spend for multiple trucks, fuel surcharge calculation (OOIDA methodology), and fleet-card savings overlays. The trip calculator here is optimized for per-route, per-vehicle calculations. For a single truck, multiply the trip cost output by the number of similar trips per month to get a monthly estimate.