Cost per mile (CPM) combines fixed costs (truck and trailer payment, insurance, permits, ELD, parking, admin) and variable costs (fuel, maintenance, tires, tolls, DEF), then divides by total miles — loaded plus deadhead — for the same period.
Two things move it: fuel price, and utilization. The same fixed costs spread over fewer miles push CPM up, which is why a truck that sits earns a worse cost structure even when nothing else changed.
Dividing by loaded miles only understates CPM and leads to accepting loads that do not cover the truck. The honest denominator is every mile the truck turned.
Example
Over a quarter a truck runs 30,000 miles and incurs $54,000 in total operating cost. CPM is $1.80. A load offered at $1.95 per mile all-in, requiring 8% deadhead to start, actually pays about $1.80 per total mile — right at breakeven, not the profit the headline number implied.
Why it matters
CPM is the pricing floor. Without it, a dispatcher cannot tell a profitable load from one that quietly loses money after fuel and deadhead.
In Trailflow, this shows up in accounting and settlements.