Time calculator
Add or subtract durations and measure the time between two clock times — results update as you type.
Add or subtract durations
Left button copies hh:mm:ss, right button copies decimal hours.
Time between two clock times
Enter a start and end time to see the duration — ideal for logging a shift on a timesheet.
All calculations run locally in your browser — nothing is uploaded.
How it works
- Enter durations as hours, minutes and seconds, one per row. Tap the +/− button on a row to subtract it, and add as many rows as you need.
- Read the live total below the rows — normalized with days spilled out, and as decimal hours ready for a timesheet.
- To measure a shift, enter a start and end clock time in the second section and enable the overnight toggle if it crosses midnight.
Frequently asked questions
- How do I add hours and minutes without converting anything?
- Type each duration into its own row — hours, minutes and seconds in separate fields — and the total updates instantly. The tool handles all the carrying for you, so 45 minutes plus 30 minutes correctly becomes 1 hour 15 minutes, never 75 on the clock.
- What are decimal hours and why do timesheets use them?
- Decimal hours express a duration as a plain number, so 7 hours 30 minutes becomes 7.50. Payroll systems and invoices multiply hours by an hourly rate, which only works with decimals — that is why the total is shown in both formats, ready to paste into a timesheet.
- How does the overnight toggle work for night shifts?
- With the toggle on, an end time earlier than the start time is treated as belonging to the next day, so 22:00 to 06:00 correctly gives 8 hours. With it off, the tool assumes both times fall on the same day and warns you when the end comes before the start.
- Can I enter minutes or seconds greater than 59?
- Yes. Values like 90 minutes or 200 seconds are accepted and normalized automatically, so 90 minutes simply counts as 1 hour 30 minutes in the total. This is handy when a log gives you raw minutes and you don’t want to convert them by hand first.
- Is anything I type sent to a server?
- No. All calculations run locally in your browser with plain arithmetic — nothing is uploaded, stored or tracked. Work hours and schedules stay on your device, and the page keeps working even if you go offline after loading it.
About this tool
Time arithmetic trips people up because clocks don’t work in base ten: 60 seconds make a minute, 60 minutes make an hour, and 24 hours make a day. Adding 1:45 and 2:30 in an ordinary calculator gives nonsense, and subtracting a lunch break from a shift by hand invites off-by-one errors. This time calculator does both jobs properly — it sums any number of durations, each of which can be added or subtracted, and it measures the elapsed time between two clock times, including shifts that cross midnight.
The duration section works like a column of figures. Each row holds hours, minutes and seconds, with a sign button to flip a row between addition and subtraction — useful for deducting breaks or correcting an earlier entry. The total is shown fully normalized, with seconds and minutes carried over and whole days spilled out separately, and alongside it as decimal hours. Everything is computed instantly in your browser as you type; nothing is sent anywhere, so work logs and schedules stay private.
The most common use is timesheets. Add each day’s worked hours as a row, subtract unpaid breaks with a minus row, and read the weekly total in decimal hours — the format payroll software and invoices expect, where 37 hours 30 minutes is written 37.50. The clock-time section covers the other half of the job: enter when a shift started and ended and the duration appears immediately, with the overnight toggle handling night shifts like 22:00 to 06:00.
A few practical tips. You can type values over 59 — 90 minutes normalizes to 1 hour 30 minutes automatically, so raw minute counts from a log paste straight in. A negative total is displayed with a leading minus sign, which tells you the subtracted rows outweigh the added ones. And the copy buttons put the formatted result on your clipboard in one tap, ready for a spreadsheet cell or an email.