CDL Trip Planner

Max On-Duty Hours (14) is a window, not a budget you can spend entirely on driving -- it's the total span of time from when a driver comes on duty until they must stop driving for the day, and it includes loading, unloading, fueling, inspections, and breaks in addition to actual driving time. Max Driving Hours (11) is the cap on time actually spent behind the wheel within that 14-hour window, which is why it's always the smaller of the two. Both figures come directly from FMCSA's hours-of-service rule for property-carrying drivers, 49 CFR § 395.3.

It divides total required driving hours by an effective daily driving allowance, which is the smaller of your Max Driving Hours setting or one hour less than your Max On-Duty Hours setting (reserving time for pre-trip and post-trip duties inside the duty window). The result is rounded up to the next full day, since a partial day of driving still requires a full driving day on the schedule.

Not necessarily in a straight line -- it reduces Total Driving Time continuously, but Driving Days Required only drops when the reduced driving time crosses below a whole-day threshold, since the calculator rounds days up. A small speed increase can leave the day count unchanged even though total driving hours went down, until the reduction is enough to eliminate an entire day.

It models single-trip HOS limits (the 11-hour driving and 14-hour on-duty rules) and adds mandatory breaks and fuel stops, but it does not model the 60-hour/7-day or 70-hour/8-day cumulative duty limits, sleeper-berth split options, adverse driving conditions exceptions, or real-world delays like traffic and dock wait times -- treat its output as a planning baseline, not a compliance guarantee.