Calculating work hours accurately is essential for both employees and employers. Get it wrong, and either you’re underpaid or the business overpays. Yet work hour calculations involve more than simple subtraction — you need to account for breaks, overnight shifts, overtime rules, and the conversion between clock time and decimal hours for payroll.

This guide walks through every aspect of calculating work hours, with practical examples and best practices for accurate payroll.

How to Calculate Hours Worked

The basic formula for hours worked is:

Hours worked = End time − Start time − Break time

Sounds simple, but the details matter. Let’s break it down.

Step 1: Record Start and End Times

Use the 24-hour format to avoid AM/PM confusion:

12-Hour	24-Hour
8:00 AM	08:00
12:00 PM	12:00
1:00 PM	13:00
5:00 PM	17:00
11:00 PM	23:00

Step 2: Subtract Start from End

Example: 9:00 AM to 5:00 PM

17:00 − 09:00 = 8 hours

Step 3: Subtract Unpaid Breaks

If you took a 30-minute unpaid lunch:

8 hours − 0.5 hours = 7.5 hours of paid work

Full Example

Item	Value
Clock in	8:45 AM
Clock out	5:15 PM
Lunch break (unpaid)	45 minutes
Gross time	8 hours 30 minutes
Paid hours	7 hours 45 minutes

To convert 7 hours 45 minutes to decimal: 7 + (45 ÷ 60) = 7.75 hours

Handling Overnight Shifts

Overnight shifts break the simple subtraction method because the end time is on the following day. The trick is to add 24 hours to the end time when it’s less than the start time.

Example: Night Shift

Start: 10:00 PM (22:00)
End: 6:00 AM (06:00 the next day)

Since 06:00 < 22:00, add 24 hours: 06:00 + 24:00 = 30:00

30:00 − 22:00 = 8 hours

Example: Split Shift Crossing Midnight

Start: 11:30 PM (23:30)
End: 7:45 AM (07:45 the next day)

Add 24 hours: 07:45 + 24:00 = 31:45

31:45 − 23:30 = 8 hours 15 minutes

Using Day Numbers

For multi-day shifts, assign each day a number and calculate in total hours:

Day 1, 22:00 = 22.0 hours from start of week
Day 2, 06:00 = 24.0 + 6.0 = 30.0 hours from start of week
Duration: 30.0 − 22.0 = 8 hours

Converting Time to Decimal Hours for Payroll

Payroll systems require decimal hours, not hours and minutes. The conversion is straightforward but must be done correctly.

The Conversion Formula

Decimal hours = hours + (minutes ÷ 60)

Quick Reference Table

Hours:Minutes	Decimal Hours
1:00	1.00
1:15	1.25
1:30	1.50
1:45	1.75
2:00	2.00
7:30	7.50
7:45	7.75
8:00	8.00
8:15	8.25
8:30	8.50

Common Mistake: Treating Minutes as Hundredths

Wrong: 8 hours 30 minutes = 8.30 hours Right: 8 hours 30 minutes = 8.50 hours

If your hourly rate is $20 and you worked 8 hours 30 minutes:

Correct: 8.50 × $20 = $170.00
Wrong: 8.30 × $20 = $166.00 (you lose $4)

Converting Decimal Back to Time

To convert decimal hours back to hours and minutes:

Minutes = (decimal part × 60)

Example: 7.4 hours

7 hours + (0.4 × 60) = 7 hours 24 minutes

Overtime Calculation

Overtime rules vary by country and jurisdiction, but the most common standard in the United States is:

Regular rate for the first 40 hours in a workweek
Overtime rate (1.5× regular rate) for hours beyond 40

Example: Weekly Overtime

Day	Hours Worked
Monday	9
Tuesday	8
Wednesday	10
Thursday	8
Friday	7
Total	42

Regular hours: 40 Overtime hours: 2

If the regular rate is $18/hour:

Regular pay: 40 × $18 = $720
Overtime pay: 2 × $18 × 1.5 = $54
Total pay: $774

Daily Overtime (California and Some Other States)

Some jurisdictions require daily overtime:

Over 8 hours in a day: 1.5× regular rate
Over 12 hours in a day: 2× regular rate
First 8 hours on the 7th consecutive day: 1.5×
Over 8 hours on the 7th consecutive day: 2×

Always check your local labor laws — overtime rules differ significantly between states and countries.

Double Time

Some employers offer double-time pay (2× regular rate) for:

Holidays
Sundays (in certain industries)
Shifts over 12 hours

Break Time Legal Requirements (United States)

Break requirements vary by state, but here’s the general framework:

Federal Law (FLSA)

The Fair Labor Standards Act does not require:

Meal breaks
Rest breaks

However, if employers offer short breaks (5–20 minutes), they must be paid.

Meal Breaks

Unpaid: Typically 30 minutes or more, where the employee is completely relieved of duties
Paid: If the employee must remain on duty (e.g., eating at their desk while monitoring systems)

State Requirements

Many states have stricter rules than federal law:

State	Meal Break Requirement
California	30 min unpaid after 5 hours, 2nd after 10 hours
New York	30 min unpaid after 6 hours
Washington	30 min unpaid after 5 hours
Oregon	30 min unpaid after 6 hours
Colorado	30 min unpaid after 5 hours

Rest Breaks

Some states require paid rest breaks:

State	Rest Break Requirement
California	10 min paid for every 4 hours
Washington	10 min paid for every 4 hours
Oregon	10 min paid for every 4 hours
Colorado	10 min paid for every 4 hours

Nursing Mothers

Under the PUMP Act, employers must provide reasonable break time and a private space (not a bathroom) for nursing mothers to express milk for one year after birth.

Timesheet Tips and Best Practices

1. Use the 24-Hour Format

Eliminate AM/PM confusion by using 24-hour time on all timesheets:

9:00 AM → 09:00
5:00 PM → 17:00

2. Round Consistently

If you round, follow the “7-minute rule” (allowed under FLSA):

1–7 minutes past the quarter hour → round down
8–14 minutes past → round up to the next quarter hour

Actual Time	Rounded Time
8:01–8:07	8:00
8:08–8:14	8:15
8:16–8:22	8:15
8:23–8:29	8:30

3. Track Breaks Separately

Don’t lump breaks into total hours. Record:

Clock in
Break start
Break end
Clock out

This creates an audit trail and prevents disputes.

4. Document Everything

Keep detailed records for at least 3 years (FLSA requirement). Include:

Employee name
Date
Start and end times
Break times
Total hours
Pay rate
Gross pay

5. Automate Where Possible

Manual timesheets are error-prone. Consider:

Time clock apps with GPS tracking
Biometric scanners
Automated break deductions
Payroll software that handles overtime calculations

6. Define the Workweek Clearly

The FLSA defines a workweek as 168 consecutive hours (7 days × 24 hours). It can start on any day and at any time. Once established, it remains fixed — you can’t change it week to week to avoid overtime.

7. Watch for “Off-the-Clock” Work

Employees who:

Check email before clocking in
Set up equipment after clocking out
Attend mandatory training off-hours

…must be paid for that time. Off-the-clock work is a common cause of wage lawsuits.

Common Payroll Calculation Errors

1. Forgetting to Convert Minutes to Decimals

The #1 payroll mistake. Always divide minutes by 60 before multiplying by the hourly rate.

2. Miscalculating Overtime

Overtime is based on total weekly hours, not daily hours (unless state law requires daily overtime). An employee who works 10 hours Monday and 6 hours Tuesday has 16 regular hours — not 2 overtime hours.

3. Including Paid Breaks in Overtime Calculation

Paid rest breaks count toward total hours for overtime purposes. Unpaid meal breaks do not.

4. Rounding Errors

Rounding must benefit both employer and employee over time. If you always round in the employer’s favor, you’re violating labor laws.

5. Not Tracking Travel Time

Travel between job sites during the workday is paid time. The commute from home to the first job site is generally not.

Calculate Your Hours Accurately

Accurate work hour calculations protect both employees and employers. They ensure fair pay, prevent legal disputes, and build trust. Whether you’re an employee verifying your paycheck or an employer processing payroll, getting the math right matters.

Use our free Hours Calculator to calculate work hours quickly and accurately. It handles overnight shifts, break deductions, decimal conversion, and overtime — all in one place. Enter your start and end times, add breaks, and get your total paid hours and pay in seconds. No more manual math, no more payroll errors.