Carrier Cost Per Mile: Fixed vs Variable Operating Expense Model, Deadhead, and Breakeven Rate

Why Cost Per Mile Is the Number That Matters

Truckload freight is priced per mile or as a flat rate that a buyer mentally converts to a per mile figure. The carrier's cost structure, however, is a mix of expenses that do not behave the same way when miles go up or down. A truck payment is the same in a slow month and a busy month. Fuel is not. When a carrier blends those two behaviors into one average number from last year's tax return, the average is wrong for every decision that matters this week: whether to take a cheap backhaul, whether to add a truck, whether a lane is worth keeping, and what to bid on a contract renewal.

A useful cost per mile model therefore does three things. It separates fixed from variable costs so the carrier can see how cost per mile shifts with utilization. It distinguishes loaded miles from empty miles so the breakeven rate reflects what customers actually pay for. And it is refreshed from real accounting and operating data on a schedule, rather than rebuilt from scratch every time a manager asks.

Fixed Costs: What You Pay Whether the Wheels Turn or Not

Fixed costs are tied to having the equipment and the business, not to the distance traveled. In a cost per mile model, fixed cost per mile is annual fixed cost divided by total miles, which means it drops as utilization rises and climbs sharply when trucks sit.

• Tractor and trailer payment or depreciation - Use the loan or lease payment for cash planning, and depreciation for an economic view. Do not count both, and do not count principal and depreciation together.
• Insurance - Auto liability, physical damage, cargo, and related coverage. Interstate for hire carriers of general freight must maintain at least the minimum levels of financial responsibility in 49 CFR 387.9, and many shippers and brokers require higher limits by contract.
• Permits, registration, and taxes - Apportioned plates, Unified Carrier Registration, the federal heavy vehicle use tax filed on IRS Form 2290 for qualifying vehicles, state permits, and IFTA licensing. IFTA fuel tax itself behaves more like a variable cost and is often modeled with fuel.
• ELD, telematics, and software - The ELD required under 49 CFR Part 395 Subpart B, the TMS, accounting software, load boards, and mobile apps are usually per truck or per month subscriptions.
• Overhead - Office rent, non driving salaries, dispatch, safety, compliance, professional fees, and communications, allocated across trucks.

Overhead allocation deserves care. A two truck owner operator and a 60 truck fleet both have overhead, but the fleet must decide how to spread dispatcher and safety salaries across units. The simplest defensible method is equal allocation per active truck per month. A more precise method allocates by miles or revenue. Pick one, document it, and apply it consistently so month over month comparisons mean something.

Variable Costs: What Every Mile Consumes

Variable costs scale with distance. In a stable operation, variable cost per mile stays fairly constant even as total miles change, which makes it the right foundation for spot and backhaul decisions.

• Fuel - Price per gallon divided by miles per gallon. A truck averaging 6.5 miles per gallon at a diesel price of 3.90 dollars costs 0.60 dollars per mile in fuel. Track real MPG by unit from fuel card and ELD data rather than a fleet assumption.
• DEF - Diesel exhaust fluid for SCR equipped engines, usually a small fraction of fuel cost, but real.
• Tires - Purchase, retread, and service cost divided by expected tread life in miles.
• Maintenance and repair - Preventive maintenance, parts, labor, and roadside repairs. Older equipment shifts cost from fixed payments into variable repair, which is why a paid off truck is not automatically cheaper.
• Driver pay per mile - Mileage based pay plus payroll taxes, workers compensation, and benefits that scale with pay. Stop pay, detention pay, and layover are accessorial costs that should be tracked separately and matched against accessorial revenue.

Loaded Miles, Empty Miles, and the Deadhead Penalty

Customers pay for loaded miles. Trucks consume cost on every mile, including deadhead to the next pickup and repositioning after a delivery in a weak market. The model must calculate cost on total miles and price on loaded miles. The connecting variable is the deadhead percentage, empty miles divided by total miles.

The relationship is simple: cost per loaded mile equals total cost per mile divided by one minus the deadhead percentage. If deadhead is 10 percent, every loaded mile must carry 1.11 times the total cost per mile. If deadhead is 20 percent, the factor is 1.25. That is why lane density, backhaul planning, and freight network design have such a direct effect on margin. Our predictive dispatch optimization work focuses on exactly this ratio.

Be precise about which mileage source you use. Billed miles from a mileage engine, practical miles, hub odometer miles, and ELD miles will differ. Pick one standard for costing, usually ELD or odometer for total miles, and reconcile billed miles against it so out of route miles are visible instead of hidden inside the average.

Worked Example: One Truck, One Year

The figures below are a clearly labeled hypothetical example to show the arithmetic. They are not benchmarks and are not drawn from any client or industry study. Replace every number with your own ledger and operating data, or use the trucking cost per mile calculator to run your figures.

Example assumptions: 116,000 total miles, of which 100,000 are loaded and 16,000 are empty, a deadhead percentage of about 13.8 percent. Variable cost per mile in this example is fuel 0.60, DEF 0.02, tires 0.04, maintenance 0.16, and driver pay with burden 0.70, for a total of 1.52 dollars per mile.

• Total cost per mile (all miles) - 0.50 fixed plus 1.52 variable equals 2.02 dollars.
• Total annual cost - 116,000 miles times 2.02 equals 234,320 dollars.
• Breakeven per loaded mile - 234,320 divided by 100,000 loaded miles equals about 2.34 dollars. Check: 2.02 divided by (1 minus 0.138) gives the same result.
• Rate with a 10 percent target margin - 2.34 divided by 0.90 equals about 2.60 dollars per loaded mile.

Now change one variable. If the same truck runs only 100,000 total miles with the same deadhead ratio, fixed cost per mile rises from 0.50 to 0.58, and the breakeven per loaded mile rises by roughly 0.09 dollars. Nothing about the truck changed. Utilization did. This is the core insight of a fixed versus variable model: idle time is expensive even when the truck is not burning fuel.

The Breakeven and Marginal Decision Rules

Two different numbers support two different decisions. The fully loaded breakeven rate, fixed plus variable divided by loaded miles, is the floor for contract pricing and long term lane decisions. Over a year, every lane in aggregate must clear it. The variable cost per mile, adjusted for the deadhead the load creates, is the floor for short term choices such as a backhaul that would otherwise run empty. A backhaul that pays above variable cost contributes something toward fixed cost that would be incurred anyway, even if it is below the full breakeven.

The danger is letting marginal pricing become the norm. A fleet that fills too much capacity with loads priced just above variable cost will never cover the truck payment and insurance. A carrier rate matrix optimization review separates lanes that build margin from lanes that only reduce empty miles, so the sales team knows which is which.

Fuel surcharge belongs in the model as well. If customer rates are quoted as linehaul plus a fuel surcharge tied to a published diesel index, model the linehaul against non fuel cost and verify that the surcharge table actually recovers fuel cost at your fleet's real MPG. A surcharge table built for a different MPG assumption can quietly shift fuel cost into the linehaul.

Modeling Cost Per Mile in the TMS and SQL

A spreadsheet model works once. A durable model lives in the data. Most carriers already have every input in some system: miles and loads in the TMS, fuel purchases in fuel card files, repairs in a maintenance module or shop system, driver pay in settlements, and fixed expenses in the general ledger. The work is joining them by unit and period with consistent definitions.

A typical structure is a monthly fact table keyed by unit and accounting period, with columns for loaded miles, empty miles, fuel gallons and dollars, maintenance dollars, tire dollars, driver pay and burden, and allocated fixed cost. A view then calculates the ratios. A simplified example in generic SQL:

SELECT u.unit_id,
       p.period_month,
       SUM(l.loaded_miles) AS loaded_miles,
       SUM(l.empty_miles) AS empty_miles,
       SUM(l.loaded_miles + l.empty_miles) AS total_miles,
       MAX(f.fixed_cost) AS fixed_cost,
       MAX(v.fuel_cost + v.def_cost + v.tire_cost
           + v.maint_cost + v.driver_cost) AS variable_cost,
       (MAX(f.fixed_cost) + MAX(v.fuel_cost + v.def_cost + v.tire_cost
           + v.maint_cost + v.driver_cost))
         / NULLIF(SUM(l.loaded_miles), 0) AS breakeven_per_loaded_mile
FROM units u
JOIN periods p ON 1 = 1
LEFT JOIN unit_load_miles l ON l.unit_id = u.unit_id AND l.period_month = p.period_month
LEFT JOIN unit_fixed_cost f ON f.unit_id = u.unit_id AND f.period_month = p.period_month
LEFT JOIN unit_variable_cost v ON v.unit_id = u.unit_id AND v.period_month = p.period_month
GROUP BY u.unit_id, p.period_month;

Aggregate each source to unit and month before the final join, as the example implies, so fuel and maintenance rows do not multiply against load rows. Use NULLIF to avoid divide by zero for units that were down all month, and report those separately because they carry fixed cost with no miles. A SQL data mining engagement usually finds the data quality issues first: fuel purchases not tied to a unit, repairs coded to the wrong truck, or empty miles never recorded because dispatch only entered loaded legs.

The accounting side matters as much as the operations side. Fixed cost by unit is only trustworthy when the general ledger codes expenses to units or classes consistently. Transportation accounting integration connects the TMS to the ledger so that settlements, fuel, and repair costs post with unit and period dimensions that the cost model can read without manual re keying. Once the view exists, a reporting dashboard can show cost per mile by unit, terminal, and month next to revenue per loaded mile, so margin gaps surface early.

Using Public Benchmarks Responsibly

The American Transportation Research Institute publishes an annual Operational Costs of Trucking report, which breaks marginal costs into categories similar to those above and is widely used as a public reference point. It is helpful for checking whether a category in your own model is wildly out of line. It is not a substitute for your own data. Fleet type, region, equipment age, driver pay structure, and freight mix all move costs, and a benchmark average describes no specific carrier. Use the report for context and your ledger for pricing.

Common Modeling Mistakes

• Dividing by loaded miles only for every cost - This hides deadhead inside cost and makes empty mile reduction invisible.
• Ignoring idle units - A parked truck still carries its payment and insurance. Fleet averages that exclude idle units overstate profitability.
• Double counting equipment cost - Using both principal payments and depreciation inflates fixed cost.
• Static fuel assumptions - Fuel moves weekly. Rebuild the fuel component from current prices and actual MPG.
• Mixing accessorials into linehaul - Detention and stop pay should be matched against accessorial revenue, not buried in mileage cost.

Related practice areas for this work include Transportation Accounting Integration, SQL Data Mining, and Carrier Rate Matrix Optimization. Each practice page describes scope, deliverables, and how an engagement starts with a short discovery call.

How Strong Tower Consulting Helps

Strong Tower Consulting helps carriers turn cost per mile from an annual estimate into a monthly operating number that lives inside the TMS and accounting systems. The work starts with a data inventory of mileage, fuel, maintenance, settlements, and ledger coding, moves to a pilot view on a subset of units, and then expands to fleet wide reporting that dispatch, sales, and management can read. Strong Tower Consulting, LLC and Exspeedite LLC are separately organized sister companies under common ownership. That separation keeps consulting advice vendor neutral and focused on the carrier operation.

To discuss your fleet, your lanes, and your current cost data, contact us or call 763-244-1373 and ask for Scott Elliott. A short call is enough to identify the data you already have and the gaps to close before your next contract renewal or rate review.

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