The basic formula is simple. Divide your total operating costs by the total miles driven. If you spent $15,000 last month and drove 12,000 miles, your cost per mile was $1.25. The challenging part is making sure you capture all your costs correctly.

Fixed costs stay relatively constant regardless of how many miles you drive. These include truck payments or lease costs, insurance premiums, annual permits and licenses, and any base plates or IFTA fees. Add these up for the month or divide annual costs by 12 to get a monthly figure.

Variable costs change based on how much you drive. Fuel is the biggest one and often runs 30 to 40 percent of your total cost per mile. A good trucking bookkeeping system tracks fuel purchases separately so you can see this number clearly. Maintenance and repairs, tires, and oil changes all fall here too. So do tolls and scale fees for specific routes.

Driver pay is a cost too, whether you’re paying yourself or employees. If you pay per mile, this is easy to calculate. If you pay hourly or salary, you’ll need to allocate that cost across miles driven. Don’t forget to include payroll taxes and any benefits you provide.

Some costs fall in between fixed and variable. Tires wear based on miles but get replaced in chunks. Tractors depreciate over time and usage. For calculation purposes, most operators spread these costs monthly using averages from their historical data.

To calculate accurately, you need clean records. Track every expense category in your accounting software and record total miles monthly from your odometer readings or ELD data. Pull reports that show your total expenses by category for the period, then divide by miles.

Run this calculation monthly. Annual averages hide seasonal variations in fuel costs and maintenance patterns. Monthly tracking shows you trends and helps you catch problems early. You’ll also see how deadhead miles affect your numbers and whether certain lanes are worth running.

Knowing your true cost per mile tells you what rates to accept and which loads make money. If your cost is $1.35 and a broker offers $1.25, you’re losing money on that haul no matter how convenient it seems. Many owner-operators underestimate their costs and take loads that feel productive but actually drain cash.

If tracking all this feels like too much on top of running routes and managing dispatch, working with a bookkeeper for small business can help. The right setup makes this calculation straightforward from your existing records rather than a monthly headache.