How to calculate time
- Pick Add or subtract durations or Time between two clock times.
- Enter the first time or duration.
- Enter the second time or duration.
- Press Calculate.
- Copy the result or the decimal hours for your timesheet.
What this time calculator gives you
- Adds and subtracts time with no manual carrying.
- Measures between two clock times even past midnight.
- Decimal hours for payroll and invoices.
- Totals in minutes and seconds.
- Negative results shown with a clear minus sign.
- Instant updates as you change any field.
Why time math goes wrong on paper
Time runs in base 60. People think in base 10. Say you add 2 hours 45 minutes to 1 hour 20 minutes. You must carry at 60 and not at 10. A total of "3 hours 65 minutes" is easy to write and easy to miss.
Subtraction is worse. The borrow step works the same way in reverse. Take 45 minutes from 2 hours 20 minutes. You must borrow 60 minutes and not 100. Under time pressure most timesheet errors start right here.
Timesheets want decimal hours
Payroll systems and invoice apps use decimal hours. Most contracts do too. The conversion is not intuitive.
| Minutes | Decimal hours | Common mistake |
|---|---|---|
| 15 | 0.25 | 0.15 |
| 20 | 0.33 | 0.2 |
| 30 | 0.5 | 0.3 |
| 45 | 0.75 | 0.45 |
Twenty minutes is a third of an hour. So 1 hour 20 minutes is 1.33 hours and not 1.2. An entry of 1.2 bills about eight minutes too little on every entry. That adds up fast over a month. The time calculator works out the decimal for you.
Shifts that cross midnight
A shift from 10:30 PM to 6:15 AM lasts 7 hours 45 minutes. Simple subtraction gives a negative number instead. It assumes both times fall on the same day.
This tool reads an end time earlier than the start as the next day. Night shifts, red eye flights and long processes all work that way. Do you really want a negative gap? Swap the two fields.
Where a time calculator helps
- Timesheets and freelance invoices that need decimal hours.
- Night shifts and rotating schedules.
- Kitchen and lab work where several steps stack up.
- Trip planning with legs and layovers.
- Overtime checks against contracted hours.
- Study plans and workout logs.
Overtime made simple
Under the US Fair Labor Standards Act most hourly workers earn overtime after 40 hours in a week. Add up each day with the time calculator. Subtract 40 hours from the total. The rest is overtime at one and a half times the regular rate. Some states also count overtime by the day. Check your state rules.
What this tool does not handle
It works with durations and clock times only. It does not use calendar dates. A period longer than 24 hours shows as total hours. That suits billing. It feels awkward for schedules.
Time zones play no part. The tool assumes both times sit in the same zone. For gaps across several days use the date calculator.
A quick time calculator example
You worked 8:50 AM to 12:15 PM and 1:00 PM to 5:40 PM. Measure each block first. The morning comes to 3 hours 25 minutes. The afternoon comes to 4 hours 40 minutes. Add them in duration mode. The total is 8 hours 5 minutes or 8.08 decimal hours.
Tips for accurate timesheets
- Log start and end times as they happen.
- Record unpaid breaks as their own entries.
- Round only the way your employer's policy says.
- Keep two decimal places for billing.
Small errors repeat every day on a timesheet. A two minute slip each shift adds up to hours over a year. A quick check with the tool keeps your pay and your invoices right.
Common time calculator questions
Why is my result negative?
You took a longer duration from a shorter one. The minus sign makes that clear.
Can I enter seconds?
Yes. Each duration has an hours, minutes and seconds box.
Who uses a time calculator?
Hourly workers check paychecks. Freelancers bill clients. Managers plan shifts. Coaches track training time. Students plan study blocks.
Your times stay private
The tool runs in your browser and sends nothing. Need an exact age? Use the age calculator. Need to read a Unix time in a log? The timestamp converter helps.