How to add up a time card by hand
A time card calculator is really just doing three simple steps for every day, then adding the days together. Once you know the steps, you can check any paycheck or timesheet yourself:
- Convert both times to minutes. Count minutes from midnight — so 8:30 AM is 8 × 60 + 30 = 510 minutes, and 5:15 PM (17:15 in 24-hour time) is 17 × 60 + 15 = 1,035 minutes.
- Subtract start from end. 1,035 − 510 = 525 minutes on the clock, from first punch-in to last punch-out.
- Subtract any unpaid break. A 45-minute lunch brings that down to 525 − 45 = 480 minutes of actual work.
Finally, convert the answer back to hours by dividing by 60: 480 ÷ 60 = 8.0 hours. So an 8:30 AM to 5:15 PM shift with a 45-minute lunch comes out to exactly 8 hours worked — which is exactly what the calculator above will show you if you enter those three values. Do this for each day, then add the daily totals to get your hours for the week.
Decimal hours vs. hours and minutes
Time cards are usually written the way people talk about time — hours and minutes, like "8 hours 45 minutes." Payroll systems, on the other hand, almost always run on decimal hours, where a fraction of an hour is expressed as a decimal instead of minutes — 7.75 hours instead of 7 hours 45 minutes. That's why this calculator's big number is a decimal: it's the number your paycheck math will actually use.
The conversion is simple once you know the pattern: divide the minutes by 60. A handy shortcut is that every 6 minutes equals exactly 0.1 of an hour, since 60 minutes ÷ 6 = 10 tenths. Here's a quick reference for common values:
| Minutes | Decimal hours |
|---|---|
| :06 | 0.10 |
| :15 | 0.25 |
| :30 | 0.50 |
| :45 | 0.75 |
| :54 | 0.90 |
So 7 hours 45 minutes is 7 + 0.75 = 7.75 hours, and 8 hours 6 minutes is 8 + 0.1 = 8.1 hours. The calculator above does this conversion for you automatically, both for each day and for your weekly total.
Are your breaks paid or unpaid?
Whether a break should be subtracted from your hours depends on how long it is and what it's for. As a general rule of thumb under US federal guidance:
- Short breaks (roughly 5 to 20 minutes)are usually considered paid work time, since they're treated as benefiting the employer and you're not free to leave for the whole break.
- Bona fide meal periods (typically 30 minutes or more) can be unpaid, but only if you're genuinely relieved of all duties — if you're expected to keep working through lunch, it usually has to be paid.
States and individual employers can set stricter rules than the federal baseline, and some require paid rest breaks or specific meal-break timing. This calculator simply subtracts whatever break minutes you enter, so use it with whatever break length actually applies to your job — paid breaks generally shouldn't be entered at all, since they don't reduce your paid hours.
How overtime works on a time card
Under the federal baseline that covers most hourly (non-exempt) workers in the US, overtime kicks in once your hours for a single week go over 40 — not per day, and not averaged across two weeks. Every hour past that 40-hour line is typically paid at 1.5 times your regular hourly rate, commonly called "time and a half."
That's exactly what the calculator above tracks: enter your days, set the overtime threshold (40 hours by default, though some states and union contracts use different rules — including daily overtime), and it splits your weekly total into regular hours and overtime hours automatically. Add your hourly rate and it estimates gross pay for both parts, with overtime hours paid at 1.5×. If you want to explore overtime pay on its own — including double-time scenarios — our overtime pay calculator covers that in more detail.