Adding up work hours sounds simple until the clock fights back — 60 minutes to an hour (not 100), shifts that cross midnight, lunch breaks to subtract, and payroll wanting everything in decimals. This guide walks through every work-hours calculation you’ll actually need, with clear formulas and examples. When you want an instant answer, use our free Hours Calculator.

How to Calculate Hours Between Two Times

The reliable method is to convert both times into minutes since midnight, subtract, then convert back to hours and minutes:

Total minutes = (End hour × 60 + End minutes) − (Start hour × 60 + Start minutes)

Worked example: a 9:00 AM start and 5:30 PM finish. In 24-hour terms that’s 17:30 and 09:00.

• End: 17 × 60 + 30 = 1050 minutes
• Start: 9 × 60 + 0 = 540 minutes
• Difference: 1050 − 540 = 510 minutes = 8 hours 30 minutes

Subtract a 30-minute unpaid lunch and you’ve worked 8 hours flat. Our Hours Calculator handles the break deduction for you.

Converting Minutes to Decimal Hours

Payroll almost always wants decimal hours, not “8 hours 30 minutes.” To convert, divide the minutes by 60:

Decimal hours = total minutes ÷ 60

So 30 minutes is 0.50, 15 minutes is 0.25, and 45 minutes is 0.75. That makes 8 hours 30 minutes equal to 8.50 decimal hours, and 8 hours 15 minutes equal to 8.25. Getting this wrong is one of the most common timesheet errors — entering “8.30” instead of “8.50” for eight and a half hours quietly underpays you.

Handling Overnight Shifts (Past Midnight)

If your shift runs 10:00 PM to 6:00 AM, subtracting straight away gives a negative number, because the end time is on the next calendar day. The fix is to add 24 hours (1,440 minutes) when the end is earlier than the start:

6:00 AM is 360 minutes; 10:00 PM is 1,320 minutes. 360 − 1,320 = −960, then + 1,440 = 480 minutes = 8 hours. The calculator’s overnight option does this automatically.

Totalling a Weekly Time Card

To total a week, calculate each day’s worked hours (clock-out minus clock-in, minus breaks), then add the days together. Keep each day in minutes while you add, and convert the weekly total to decimal at the end to avoid rounding drift. Our Hours Calculator has a weekly time card mode that does exactly this — enter each day’s in/out and break, and it shows a daily breakdown plus the weekly total.

How Overtime Works

Under the US Fair Labor Standards Act, non-exempt employees earn 1.5× their regular rate for hours over 40 in a workweek. Some states also apply daily overtime for hours over 8 in a single day. Here’s a quick example at a $20/hour rate working 45 hours in a week:

• Regular: 40 hours × $20 = $800
• Overtime: 5 hours × $20 × 1.5 = $150
• Gross total: $950

Overtime rules differ by country and state, so treat these as common conventions, not legal advice. The Hours Calculator supports both the weekly-40 and daily-8 rules.

12-Hour vs 24-Hour (Military) Time

Military time removes AM/PM ambiguity. To convert a PM time to 24-hour, add 12 to the hour (1:00 PM becomes 13:00); 12 PM stays 12:00 and 12 AM becomes 00:00. To go back, subtract 12 from times after noon and add PM. The calculator accepts whichever format your device uses, so you rarely need to convert by hand.

From Hours to Take-Home Pay

Once you know your gross hours and pay, the next question is what actually lands in your bank account after tax and deductions. That’s a different calculation — and our Paycheck Calculator handles it. A natural workflow is: total your hours here, then drop the gross figure into the Paycheck Calculator for your net pay.

Quick Reference: Minutes to Decimal