Dot Hours of Service Calculator checks the next HOS stop from 11-hour, 14-hour, 60/70-hour cycle, and 8-hour break limits. Formula: available drive time = min(11-hour left, 14-hour left, cycle left, break left).
All Four Clocks Running Against You
Most drivers track the 11-hour driving limit and call it good. But federal HOS rules layer four independent constraints that all run simultaneously from the moment you go on duty. A driver with 5 hours left on the 11-hour limit can still be stopped dead by a 14-hour shift window that closes in 40 minutes, or a break clock ticking toward the 8-hour mark. The tightest constraint wins — always.
This calculator resolves all four federal limits at once and returns the single number that actually matters: how long you can drive before your next mandatory stop.
Formulas Used
11-Hour Driving Rule
- Remaining Drive Time = 11 − Driving Time Today
- Limit Consumed (%) = (Driving Time Today ÷ 11) × 100
14-Hour Shift Rule
- Remaining Shift Window = 14 − Hours Since Coming On Duty
- Shift Consumed (%) = (Hours Since Coming On Duty ÷ 14) × 100
8-Hour Break Rule
- Remaining Before Mandatory Break = 8 − Drive Time Since Last Break
- Break required: 30 consecutive minutes off duty or in sleeper berth
Cycle Rule
- Total Cycle Hours = Prior Cycle Hours + Driving Time Today + On-Duty Non-Driving Time Today
- Remaining Cycle = Cycle Limit − Total Cycle Hours
- Cycle Consumed (%) = (Total Cycle Hours ÷ Cycle Limit) × 100
- Cycle Limit = 70 (8-day rule) or 60 (7-day rule)
Available Drive Time
- Available Drive Time = min(Remaining 11-Hour, Remaining Shift Window, Remaining Cycle, Remaining Before Mandatory Break)
- Any individual result below zero is floored to 0 before the minimum is taken
Violation Condition
- Violation alert fires when: Available Drive Time ≤ 0 OR Remaining Before Mandatory Break ≤ 0
Input Validation
- Hours Since Coming On Duty must be ≥ (Driving Time Today + On-Duty Non-Driving Time Today)
How It Works
Six inputs drive the entire calculation. The cycle rule selection sets whether your rolling window is 70 hours across 8 days or 60 hours across 7 days — this affects only the cycle limit in the formula, not the other three rules. Prior cycle hours are the accumulated on-duty total from all days before today; today’s hours are entered separately.
Driving time today and on-duty non-driving time today are kept separate because they feed into the rules differently. Only driving time counts toward the 11-hour driving limit and the 8-hour break clock. Both driving and on-duty non-driving count toward the cycle total — pre-trip inspections, fueling, loading, dispatch time, and any other on-duty activity all burn cycle hours.
Hours since coming on duty is the full wall-clock time from when you first went on duty this shift. The 14-hour window is calculated from this figure, not from accumulated active work time. Drive time since last break tracks only driving accumulation against the 8-hour break threshold — non-driving on-duty periods don’t reset this clock, but a qualifying 30-minute break does.
Once all four remaining-hours figures are computed, the calculator takes the minimum of all four. That minimum is the available drive time displayed at the top. Each individual constraint is shown separately so you can see exactly which one is binding and how much headroom you have on the others.
The 14-Hour Window Is a Wall, Not a Countdown
A widespread misread of FMCSA rules: drivers assume that resting during a shift pauses the 14-hour clock. It does not. The 14-hour window is an absolute rolling window from first going on duty. If your shift starts at 5:00 AM, driving is prohibited after 7:00 PM that evening regardless of how many rest stops you took.
This means the “Hours Since Coming On Duty” input requires the true elapsed time since your shift began — including any rest periods that occurred mid-shift that didn’t qualify as a full 10-hour off-duty restart. Entering only your active work time here produces an incorrect (overly optimistic) 14-hour result. If you came on duty at 5:00 AM and it’s now 1:00 PM, the input is 8 hours, even if 1.5 of those hours were spent off the clock at a rest stop.
Worked Example
A long-haul driver on the 70-hour/8-day cycle stops to check their status at 2:30 PM and enters the following:
- Prior cycle hours (all days before today): 52
- Driving time today: 6 hours
- On-duty non-driving today: 1.5 hours
- Hours since coming on duty: 8 hours
- Drive time since last break: 6 hours
The four constraints resolve as:
- 11-Hour Rule: 11 − 6 = 5 hours remaining, 54.55% consumed
- 14-Hour Rule: 14 − 8 = 6 hours remaining, 57.14% consumed
- Break Rule: 8 − 6 = 2 hours remaining
- Cycle Rule: 52 + 6 + 1.5 = 59.5 total; 70 − 59.5 = 10.5 hours remaining, 85.00% consumed
Available Drive Time = min(5, 6, 2, 10.5) = 2 hours. The break requirement is the binding constraint. Despite having 5 hours left under the daily driving limit and 10.5 hours left in the cycle, this driver must take a 30-minute qualifying break within the next 2 hours of driving or cease driving entirely. After the break, drive time since last break resets to 0 and the break clock begins again from 8.
Frequently Asked Questions
Why does the calculator show a logic error when I enter my hours?
The calculator checks that Hours Since Coming On Duty is not less than the sum of Driving Time Today and On-Duty Non-Driving Time Today. Physically, the total time you’ve spent actively working cannot exceed the total time elapsed since your shift started. When that condition is violated — usually from entering the wrong figure in one of the three fields — the calculator blocks calculation rather than produce a nonsensical result. Double-check that elapsed time reflects wall-clock time from when you first went on duty, not just active work time.
Does on-duty non-driving time affect my available drive time?
Not directly through the 11-hour or break rules — those only count driving hours. But on-duty non-driving time is added to your cycle total alongside today’s driving hours. If your cycle is already tight, fueling stops, inspections, and loading time can push you into a cycle violation even while your daily driving hours look fine. The cycle calculation is: Prior Cycle Hours + Driving Time Today + On-Duty Non-Driving Time Today, compared against the 70- or 60-hour limit.
What happens if I’ve already exceeded a limit before calculating?
Any remaining-hours figure that would go negative is floored to zero. The available drive time output shows 0.00 hours and a violation alert appears. Percentage-consumed figures cap at 100%. The calculator doesn’t produce negative outputs — it flags the condition and stops.
Does switching from 70-hour to 60-hour change anything besides the cycle math?
Only the cycle limit changes — from 70 to 60 in the remaining cycle and consumed percentage formulas. The 11-hour driving rule, 14-hour shift window, and 8-hour break rule are identical under both cycle options. The binding result may shift if the cycle becomes the tightest constraint under the 60-hour selection, but the other three calculations are unaffected by that dropdown.