Hours Calculator

Accurate time tracking is the foundation of fair payroll, correct client billing, and reliable project estimates. In May 2026, the US Department of Labor's Wage and Hour Division published a technical amendment formally restoring the 2019 FLSA salary thresholds for white-collar overtime exemptions: $684 per week ($35,568 annually) for standard exemptions and $107,432 annually for highly compensated employees. The 2024 rule that would have raised the threshold to $1,128 per week was vacated by federal courts, meaning millions of salaried workers remain eligible for overtime pay when they exceed 40 hours per week. Even small rounding errors in time tracking can compound into significant payroll discrepancies over weeks and months. An hours calculator eliminates the mental arithmetic of converting minutes and handles spans that cross midnight automatically.

What This Calculator Does

Enter a start time and end time for each work period or activity. The calculator finds the elapsed time for each row and sums all rows into a total. Both 12-hour (AM/PM) and 24-hour formats are supported. The result shows hours per period, total hours and minutes, and decimal hours for payroll and billing purposes.

For related time and payroll tools, try our Time Card Calculator for weekly time cards with overtime calculation, or our Time Calculator for adding and subtracting arbitrary time durations. You can also use our Salary Calculator to convert hourly wages to annual salary.

Inputs Required

• Start Time: The time a period begins, in HH:MM or HH:MM AM/PM format
• End Time: The time a period ends
• Label (optional): A descriptive name for each period such as "Morning Shift" or "Client Meeting"

Outputs Provided

• Hours per Period: The decimal hours for each individual entry
• Total Hours and Minutes: The combined duration in H:MM format
• Decimal Hours: The total expressed as a single decimal number for billing

How the Calculation Works

Each start and end time is converted to minutes since midnight. The difference gives the duration for that period in minutes. If the end time is earlier than the start time, the calculator assumes the period crosses midnight and adds 24 hours (1,440 minutes) to the end time before subtracting.

For example, 9:00 AM is 540 minutes from midnight and 5:00 PM is 1,020 minutes. The difference is 480 minutes, or 8.00 decimal hours. If a shift runs from 10:00 PM (1,380 minutes) to 6:00 AM (360 minutes), the calculator adds 1,440 to get 1,800, then subtracts 1,380 to get 420 minutes, or 7.00 decimal hours.

How to Use the Calculator

1. Enter a start time and end time for your first period
2. Optionally add a label like "Morning" or "Overtime"
3. Click "Add Time Period" to include additional periods
4. View the hours for each row and the running total on the right
5. Use the decimal hours value for payroll or billing calculations

Example Calculations

An employee works two shifts: 8:00 AM to 12:00 PM (4 hours) and 1:00 PM to 5:30 PM (4 hours 30 minutes). The total is 8 hours 30 minutes, or 8.50 decimal hours. At $25 per hour, gross pay would be $212.50.

A nurse works a night shift from 11:00 PM to 7:00 AM. The calculator detects the midnight crossover and returns 8 hours correctly, without the user needing to adjust the times manually. At a night shift differential of $32 per hour, gross pay would be $256.

Real-World Scenarios

Freelance Billing Across Multiple Client Sessions

A marketing consultant in Portland logs three client sessions in a single day: 10:00 AM to 11:30 AM (Client A), 1:00 PM to 3:45 PM (Client B), and 4:30 PM to 5:00 PM (Client C). The calculator returns 1.5 hours, 2.75 hours, and 0.5 hours respectively, totaling 4.75 decimal hours. At her rate of $150 per hour, the daily invoice total is $712.50. She uses the per-period breakdown to bill each client separately, ensuring accurate and transparent invoicing.

Weekly Payroll with Overtime Threshold

A small business owner in Atlanta tracks daily hours for a part-time employee across five workdays. The entries are 8:00 AM to 4:00 PM Monday through Thursday (8 hours each with a 30-minute unpaid lunch, entered as two 3.75-hour periods) and 8:00 AM to 2:00 PM Friday (5.5 hours). The weekly total comes to 35.5 hours. Since this is below the 40-hour FLSA overtime threshold, all hours are paid at the regular rate of $18 per hour, yielding $639 gross. If the employee had worked 42 hours, the owner would need to pay 2 hours at 1.5 times the regular rate ($27 per hour) under FLSA overtime rules.

Night Shift Tracking for Healthcare Worker

A hospital technician in Boston works three 12-hour night shifts per week: 7:00 PM to 7:30 AM on Tuesday, Wednesday, and Thursday. The calculator handles the midnight crossover automatically for each shift, returning 12.5 hours per shift. The weekly total is 37.5 hours. With a night shift differential of $34 per hour, gross weekly pay is $1,275. The technician uses the decimal hours output to verify her paystub against the hospital's payroll system, catching a 15-minute discrepancy on one shift that would have cost her $8.50.

Common Mistakes to Avoid

• Not accounting for lunch breaks: If lunch is unpaid, enter it as a separate period to subtract, or split your work time into before-lunch and after-lunch entries. A 30-minute unpaid lunch over 5 days adds up to 2.5 hours per week, or $1,950 per year at $15 per hour
• Confusing AM and PM: Entering 9:00 PM instead of 9:00 AM will produce a result that is 12 hours too long. Always double-check the AM/PM setting, especially when entering multiple periods quickly
• Assuming 8.5 hours is 8 hours 50 minutes: Decimal hours and clock time are different. 8.5 hours is 8 hours 30 minutes. 8.75 hours is 8 hours 45 minutes. Payroll systems use decimal hours, while humans read clock time. This calculator shows both to prevent conversion errors
• Forgetting overtime thresholds: Under the FLSA, overtime applies to hours over 40 per workweek at 1.5 times the regular rate. The DOL's May 2026 technical amendment confirmed the 2019 salary threshold of $684 per week for exempt employees. Non-exempt employees must receive overtime regardless of salary level. Check your state laws, as California, New York, and other states impose stricter overtime rules

Limitations of This Calculator

This calculator computes elapsed time between start and end times and converts the total to decimal hours. It does not automatically calculate overtime pay, shift differentials, or holiday premiums. It does not account for paid break time, which varies by state law and employer policy. The midnight crossover detection assumes a single overnight span, not multi-day shifts exceeding 24 hours. For complex payroll scenarios involving multiple pay rates, shift differentials, or weekly overtime aggregation across employees, a dedicated payroll system or time card calculator is more appropriate. State and local labor laws may impose additional requirements for meal breaks, rest periods, and overtime calculations that this tool does not address.

Authoritative Research and Resources

• US Department of Labor: Fair Labor Standards Act - The DOL Wage and Hour Division's official resource on FLSA requirements, including the May 2026 technical amendment restoring the 2019 salary thresholds of $684 per week for white-collar overtime exemptions.
• DOL: Technical Amendment on EAP Exemptions (May 14, 2026) - The official press release announcing the restoration of 2019 regulations governing executive, administrative, and professional employee exemptions under the FLSA.
• Bureau of Labor Statistics: American Time Use Survey - The BLS Time Use Survey provides detailed data on how Americans spend their working hours, including average workweek lengths, shift distributions, and overtime patterns across industries.