Hos Calculator

FMCSA Hours of Service (HOS) Calculator

Remaining Availability

function calculateHOS() { var driveTime = parseFloat(document.getElementById('drivingHours').value); var nonDriveTime = parseFloat(document.getElementById('nonDrivingHours').value); var sinceBreak = parseFloat(document.getElementById('timeSinceBreak').value); var resultsDiv = document.getElementById('hos-results'); var alertDiv = document.getElementById('hos-alerts'); if (isNaN(driveTime) || isNaN(nonDriveTime) || isNaN(sinceBreak)) { alert("Please enter valid numbers for all fields."); return; } resultsDiv.style.display = "block"; alertDiv.innerHTML = ""; // 11-Hour Rule: Maximum driving time var driveRem = 11 – driveTime; // 14-Hour Rule: Maximum duty window (starts when duty begins) var totalDuty = driveTime + nonDriveTime; var dutyRem = 14 – totalDuty; // 30-Minute Break Rule: Must take break after 8 hours of driving var breakRem = 8 – sinceBreak; // Format Display document.getElementById('res-drive-time').innerHTML = "Remaining Drive Time: " + (driveRem > 0 ? driveRem.toFixed(2) + " hours" : "0.00 hours (LIMIT REACHED)"); document.getElementById('res-duty-window').innerHTML = "Remaining On-Duty Window: " + (dutyRem > 0 ? dutyRem.toFixed(2) + " hours" : "0.00 hours (LIMIT REACHED)"); document.getElementById('res-break-time').innerHTML = "Time Until Required 30-Min Break: " + (breakRem > 0 ? breakRem.toFixed(2) + " hours" : "0.00 hours (BREAK REQUIRED NOW)"); // Warnings var alerts = []; if (driveRem <= 0) alerts.push("Violation: 11-Hour Driving Limit exceeded."); if (dutyRem <= 0) alerts.push("Violation: 14-Hour Duty Window exceeded."); if (breakRem 0) { alertDiv.innerHTML = alerts.join(""); } }

Understanding the Hours of Service (HOS) Regulations

The Federal Motor Carrier Safety Administration (FMCSA) enforces strict Hours of Service (HOS) regulations to ensure that commercial motor vehicle (CMV) drivers stay alert and safe on the road. This HOS calculator helps drivers and fleet managers track their remaining legal driving time and duty window based on property-carrying regulations.

The Three Pillars of HOS Compliance

1. The 11-Hour Driving Limit

A property-carrying driver may drive a maximum of 11 hours after 10 consecutive hours off duty. Once you have reached 11 hours of actual wheel time, you must stop driving until you have completed another 10-hour off-duty period.

2. The 14-Hour Duty Window

This is often referred to as a "daily limit." You may not drive beyond the 14th consecutive hour after coming on duty, following 10 consecutive hours off duty. Off-duty time (like lunch or breaks) does not extend this 14-hour window.

3. The 30-Minute Break Rule

Drivers must take a 30-minute break after 8 cumulative hours of driving without at least a 30-minute interruption. This interruption can be satisfied by off-duty time, sleeper berth time, or on-duty non-driving time.

Calculation Example

Scenario: A driver starts their day at 8:00 AM.

  • 8:00 AM – 12:00 PM: Driving (4 hours)
  • 12:00 PM – 1:00 PM: Loading (1 hour On-Duty)
  • 1:00 PM – 3:00 PM: Driving (2 hours)

Total Stats: 6 hours driving, 1 hour on-duty, 7 hours total window used.
Remaining: 5 hours of driving left, 7 hours left in the duty window, and 2 hours until a mandatory 30-minute break is required.

Why Use an HOS Calculator?

Managing paper logs or even checking ELD (Electronic Logging Device) readouts can sometimes be confusing when planning a route. Using an HOS calculator allows you to:

  • Prevent Violations: Avoid costly fines and "Out of Service" orders during DOT inspections.
  • Improve Trip Planning: Know exactly where you need to stop for your 10-hour break.
  • Maintain Safety: Ensure you are not pushing past physical limits, reducing the risk of fatigue-related accidents.

Disclaimer: This calculator is for informational purposes only. Drivers should always rely on their certified Electronic Logging Device (ELD) and official FMCSA guidelines for legal compliance.

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