Fuel Cost Per Mile: How to Calculate Yours (and Keep It Updated)

If you don't know what you're burning per mile, you're guessing. Here's a straight-up method to calculate your fuel cost per mile, update it for season and region, and use it to say no to junk loads.

You're looking at a load and the only number that matters is the bottom line

They want you to run 800 miles for an all-in rate that looks okay on paper. But you've got to eat the fuel. If you don't know your fuel cost per mile, you're guessing. Guessing wastes time, wears the truck, and lowers your pay.

Below is a simple, practical way to get a real fuel cost per mile for your rig — and keep it current as prices move. Do the math. Don't take anyone's word for it.

Step 1 — decide the fuel you're measuring

Most of us measure diesel for the tractor only. If you pull a pup or run a reefer that burns diesel on its own, include that later as a separate line. For a regular over-the-road diesel tractor, you're calculating diesel gallons burned per mile and multiplying by the price per gallon you pay.

Step 1 is: pick whether you're using historical average for your truck, a planned trip's estimate, or your live-updated cost. I recommend a rolling truck-average plus a trip adjustment.

Step 2 — find your gallons per mile (GPM)

You can do this two ways.

• Quick route: take a recent full-tank run. Odometer start and stop, gallons pumped to refill. Gallons pumped ÷ miles driven = GPM.
• Smarter route: use a few refuels over 3,000–6,000 miles to smooth out driving differences (empty vs loaded, hills, idling). Add up total gallons ÷ total miles = GPM.

Example: you drove 2,400 miles over a pay period and pumped 320 gallons total. 320 ÷ 2400 = 0.1333 GPM. That's 13.33 gallons per 100 miles.

Step 3 — decide which price per gallon to use

Use the price you actually pay at the pump, not the national chatter. Card discounts, highway markups, and taxes change the price. If you use a card that gets fuel discounts, use the net price after discounts and fees.

You can keep an eye on market direction for planning. For example, the EIA's weekly U.S. retail diesel number was $5.31/gal for the week of 2026-07-27 and it's been rising versus last month. That tells you to expect higher pump bills, so update your cost before you accept long runs. But don't use that EIA number as your fuel price unless it matches what you actually pay.

Step 4 — basic fuel cost per mile formula

Fuel cost per mile = Gallons per mile (GPM) × Price per gallon (PPG)

Using the worked example above: GPM = 0.1333. If you pay $5.20/gal at your card: 0.1333 × $5.20 = $0.693. So your fuel cost is about $0.69 per mile.

If you pay $6.00/gal because you're stuck in a metro or on the West Coast, same GPM gives 0.1333 × $6.00 = $0.80/mi. Big difference. That $0.11/mi swing eats into your load profitability fast.

Step 5 — add the secondary fuel hits

Don't forget the other ways fuel hits your wallet:

• Idle fuel. Estimate idle hours × gallons/hour if you idle a lot. Add that to total gallons.
• Reefer fuel. If the trailer reefer runs off diesel, either convert its gallons into GPM or keep a separate per-hour or per-mile line for the reefer.
• Deadhead. Your GPM doesn't change, but deadhead miles increase total fuel cost of the trip. Factor deadhead into trip miles when you compute per-trip fuel cost.

Example, continued: same run, but on this trip you expect 8 hours of idle at 0.8 gallons/hour for a loaded drop: that's 6.4 gallons extra. If the trip is 800 miles, add 6.4 ÷ 800 = 0.008 GPM; new GPM = 0.1413. At $5.20/gal that's 0.1413 × $5.20 = $0.73/mi.

Step 6 — keep it updated (don't let the number go stale)

Fuel prices move. Your driving mix changes. Update your fuel cost per mile on a schedule and when conditions change:

• Weekly if you run regional lanes and gas swings matter. The EIA shows weekly moves for a reason — markets can move fast. For the week of 2026-07-27 the EIA's U.S. retail diesel average was $5.31/gal and up versus four weeks ago, so you'd want to check your numbers more often when prices are climbing.
• Monthly if you run predictable long-haul lanes and your pump price isn't volatile.
• Immediately when you get a new fuel card rate, start using the new net price.

Also update after a long season of mountain runs or heavy idling; your GPM likely changed.

How to use the number when deciding on loads

Put this fuel cost per mile into your per-trip math before you say yes.

Say a broker offers $2,400 all-in for 800 miles. You do this quick check:

• Fuel: 800 miles × $0.73/mi = $584
• Toll, lumper, detention, hook/unhook, etc: add realistic numbers for your operation.
• Fixed costs: truck payment, insurance, permits — convert to per-mile and add.

If the remaining margin doesn't cover your pay target and leave room for wear and maintenance, walk. That load can look pretty on the board and still be trash once you add the fuel hit.

This is where a per-load profitability calculator helps. A tool that lets you plug in your truck's GPM, the exact pump price you pay, and the load's miles and fees will spit out the fuel line and the trip profit so you don't have to do it on paper at a truck stop. HaulProfit does exactly that kind of math from your own numbers — it doesn't guess market rates for you — so you can see the fuel line before you book.

Quick checklist you can run in 60 seconds

• What's my current GPM? (Use recent refuels.)
• What's the net PPG I pay on my card? (Include fees and discounts.)
• Multiply for fuel cost per mile. Add idle and reefer if needed.
• Multiply by trip miles. Add other trip-specific fees. Decide.

One more worked example (full trip math)

You're offered 1,200 miles for $3,600 all-in. You use your rolling GPM: 0.14. Your card price is $5.40/gal. Expect 4 hours of idle at 0.9 gph. You have a