The number that decides every load
Cost per mile is the one figure that turns a rate on a load board into a yes or a no. Without it you are guessing, and the guess is usually optimistic, because the costs that sink owner-operators are the ones that do not arrive with the load: the quarterly insurance instalment, the tire that lets go at 90,000 miles, the plates.
The reason to split fixed from variable is not bookkeeping neatness. It is that the two behave completely differently when your miles change. Variable costs are roughly honest per mile — burn more miles, buy more diesel. Fixed costs are a fixed lump that gets divided by however many miles you managed, so they punish a slow month twice: less revenue coming in, and a higher cost per mile on the miles you did run.
Work the two examples below and the effect is obvious. Identical truck, identical bills. At 10,000 miles the all-in cost is 94 cents a mile and a $1.25 rate clears about $3,100 for the month. At 6,000 miles the same truck costs $1.183 a mile, and that same $1.25 rate leaves under seven cents a mile — around $402 for a month of work. Nothing about the truck changed. Only the miles did.
How this calculator works
Fixed costs are your truck or trailer payment, insurance, and everything else in the "bills whether it rolls or not" bucket — plates, permits, IFTA and IRP, the ELD subscription, accounting. Variable costs are diesel, maintenance and your tire reserve, plus tolls, scales, lumpers and parking. The calculator totals each bucket, divides each by the miles you entered, and adds them for the all-in cost per mile. Your break-even rate per mile is that same number: below it, the month loses money.
Enter a profit target and it returns the rate per mile that covers your costs and your target together. Enter a rate you are being offered and it returns the profit or loss per mile at that rate, scaled to the month, with a plain verdict. Per-mile figures are rounded to a tenth of a cent, because across 10,000 miles a tenth of a cent is ten dollars.
What it does not do: it does not know your seasonality, it does not amortise a major overhaul for you, and it does not decide whether your own wage belongs in costs or in profit — that is your call, and the FAQ below explains both ways. It is a planning tool built on the numbers you supply, not an accounting record.