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How to Calculate Hours Worked for Payroll

Quick Calculators Team
3 min read

If you manage a team of hourly employees, or if you are a freelancer billing a client, tracking hours accurately is the most important administrative task you perform.

A tiny miscalculation of just 15 minutes a day can lead to hundreds of dollars in lost wages (or overpaid payroll) by the end of the month.

Here is how to calculate hours worked with precision, avoiding the common pitfalls of standard AM/PM time clocks.

The Problem with AM and PM

If an employee clocks in at 8:45 AM and clocks out at 4:15 PM, calculating the exact duration in your head is surprisingly difficult because our clocks reset at 12.

If you try standard subtraction (8 - 4), the math completely breaks down.

Method 1: Convert to Military Time (24-Hour Clock)

To do the math properly, you must first convert the PM times into a 24-hour format by adding 12 to any hour after 1:00 PM.

  1. Clock In: 8:45 AM remains 08:45.
  2. Clock Out: 4:15 PM becomes (4 + 12) = 16:15.

Now you can subtract the start time from the end time. However, because time operates on a base-60 system (not base-100), you cannot simply subtract the minutes if the start minutes are higher than the end minutes.

You have to "borrow an hour" (60 minutes):

  • Convert 16:15 into 15:75 (by borrowing 60 minutes).
  • Subtract the hours: 15 - 8 = 7 hours.
  • Subtract the minutes: 75 - 45 = 30 minutes.
  • Total Time: 7 hours and 30 minutes.

Method 2: Convert to Decimal Time for Payroll

While "7 hours and 30 minutes" is correct, you cannot multiply that by an hourly wage. If you try to multiply an employee's $20/hr wage by "7.30", you will severely underpay them!

You must convert the 30 minutes into a decimal format (a percentage of an hour) by dividing by 60.

  • 30 minutes ÷ 60 = 0.5 hours.
  • Total Decimal Time: 7.5 hours.
  • Payroll Calculation: 7.5 hours × $20/hr = $150.00.

Common Decimal Conversions to Memorize

To speed up payroll, memorize these standard quarter-hour conversions:

  • 15 minutes = 0.25 hours
  • 30 minutes = 0.50 hours
  • 45 minutes = 0.75 hours

Automate Your Timesheets

Manual payroll calculation is tedious and prone to expensive human errors.

If you are tired of converting military time and dividing minutes into decimals, simply plug your start and end times into our free Time Duration Calculator. It will instantly give you the exact duration in hours, minutes, and payroll-ready decimals!