Fuel is the biggest variable cost in trucking
For most owner-operators, diesel is the single largest expense on the road — often 30–40% of total operating cost. That's why knowing your fuel cost per mile, and how it moves with diesel prices and MPG, is essential for pricing loads and protecting margin. This calculator gives you the number instantly and pre-loads the latest U.S. average on-highway diesel price so your estimate reflects today's market.
Get your MPG right
The biggest swing factor here is fuel economy. A loaded Class 8 truck usually runs 5.5–7.5 MPG; we default to 6.5 as a sensible middle. For accuracy, use your own fleet MPG — total miles ÷ total gallons over a recent quarter (the same fleet-MPG figure your IFTA calculator uses). Even a 0.5 MPG improvement is real money: on 120,000 miles a year, going from 6.0 to 6.5 MPG saves over 1,500 gallons.
Lower your fuel bill
- Ease off the throttle. Above ~60 mph, every extra mph roughly costs 0.1 MPG.
- Kill idle time. Idling burns ~0.8 gal/hour for nothing.
- Keep tires inflated and the truck maintained.
- Buy fuel smart. Pump price and fuel tax both vary by state — see our fuel strategy guide and state tax rates.
Once you know fuel cost, fold it into the full picture with Cost Per Mile, price loads with Rate Per Mile, and recover rising diesel from shippers with the Fuel Surcharge calculator.
How do I calculate truck fuel cost?+
Divide total miles by MPG to get gallons used, then multiply by the diesel price per gallon. Fuel cost = (miles ÷ MPG) × price. For example, 1,000 miles at 6.5 MPG and $4.83/gal is about $743.
What MPG should I use for a semi truck?+
A loaded Class 8 semi typically averages 5.5 to 7.5 MPG, with about 6.5 a reasonable all-around estimate. Use your own fleet MPG (total miles ÷ total gallons over a recent period) for the most accurate result.
What diesel price should I enter?+
For a planning estimate, use the current U.S. average on-highway diesel price, which this tool pre-loads from the U.S. Energy Information Administration. For a specific trip, use the actual pump price you expect along your route.
How much does fuel cost per mile for a semi?+
Fuel cost per mile equals diesel price divided by MPG. At $4.83/gal and 6.5 MPG that's about $0.74 per mile. Because fuel is the biggest variable cost, small MPG gains add up fast.
How can I lower my fuel cost?+
Slow down, cut idling, keep tires inflated, reduce deadhead, and buy fuel strategically in lower-tax states. Improving from 6.0 to 6.8 MPG on 120,000 miles a year saves thousands of dollars.
Does this calculator include DEF?+
No — it estimates diesel only. DEF is consumed at roughly 2–3% of diesel volume and should be budgeted separately as a small added cost.
