How the semi truck fuel calculator works
- Road gallons = trip miles ÷ MPG
- Reefer unit gallons = unit run hours × gallons per hour (reefers only)
- Trip fuel cost = total gallons × diesel price
- Fuel cost per mile = trip fuel cost ÷ trip miles
- Fill-up cost = tank size × diesel price
Picking a truck type loads an example MPG and tank size as a starting point. Replace both with your own truck's numbers for a real answer. The diesel price starts at the latest U.S. average we've checked.
A worked example
A dry van runs a 1,300-mile trip, deadhead included, at 6.5 MPG, with diesel at $6.38 and 300 gallons of tank.
- Gallons
- 200
- Fuel cost
- $1,276
- Per mile
- $0.98
- Fill-up
- $1,914
Make it a reefer whose unit runs 30 hours over the trip at 0.8 gallons an hour, and the trip takes 24 more gallons, about $153 more. That's fuel a per-mile surcharge never sees. Drop the MPG from 6.5 to 6.0 for a heavy load through the mountains, and the road fuel alone rises by about 17 gallons.
What it costs to fill a semi truck now
Diesel moved a long way in a year. The U.S. average was $6.38 a gallon in late September 2026, against $3.75 a year earlier.
Source: U.S. EIA, U.S. On-Highway No. 2 Diesel retail price, weekly average, late September 2026, October 2026
At that price, every 100 gallons is close to $640. For a carrier with a thin cash cushion, a single fill-up can be the biggest bill of the week, which is where fuel cards, fuel advances and loads that pay fuel separately make a real difference.
Reefer unit fuel
A reefer carrier buys fuel twice: for the truck and for the unit. Continuous run mode for fresh produce, chilled meat and other temperature-sensitive cargo; start-stop mode should not be used for fresh produce, which burns more than cycling. Count the hours the unit runs over the whole trip, including the wait at a produce shed and the 10-hour break with product on board. For a fuller estimate by setpoint and conditions, use the reefer fuel burn calculator.
Source: UF/IFAS HS1328, Protecting Perishable Foods During Transport by Truck or Rail (Brecht et al.), revision of USDA Agriculture Handbook 669, October 2026
Fuel cost by truck type
Fuel economy varies a lot across the trucks we dispatch. A loaded tractor-trailer pulling a heavy flatbed or tanker load through the mountains can fall well below its flat-ground average. A 26 ft box truck usually gets better mileage but runs shorter, stop-and-go routes where idling at docks adds up. A hotshot pickup gets the best mileage of the group but carries less, so fuel is still a big share of each smaller load. Pick your truck, then correct the MPG to what your own records show.
Ways to cut trip fuel
- Plan the reload before you deliver, so the empty run to the next pickup stays short.
- Keep speed steady; a few miles an hour slower on the interstate saves more than most drivers expect.
- Fuel where your card's discount applies, not just where it's convenient.
- Cut idling at docks and on breaks where you can, and keep tires at the right pressure.
- For reefers, precool before loading and keep door openings short at multi-stop deliveries.
Planning cash for fuel
Fuel is paid at the pump, often days or weeks before the load pays. Use the trip total to check you have the cash, card limit or fuel advance to cover it before you accept a long run. Our guide to fuel advances and fuel cards covers the options.
Using your result
Fuel is usually the biggest single cost on a load, so it's the first number to check against the rate. If fuel eats half of what a load pays, there's little left for everything else. Compare the fuel cost with the load's pay, then check the full picture in the load profitability calculator.
Cutting fuel cost per load mostly comes down to fewer empty miles and less idling. That's much of what a dispatcher does: planning reloads close to your deliveries and avoiding long waits. With us, every load comes to you for a yes or no, and the broker sends the rate con straight to you. Our fee is 5% for one truck with authority older than 6 months. See pricing.