Do sums with clock-style numbers
An ordinary calculator breaks on time because 60 seconds make a minute, not 100. This page does the carrying for you. Fill in a row of hours, minutes and seconds, choose + or - for the next row, and keep adding rows until the sum is complete. An empty box counts as zero, so 45 minutes only needs the minutes box.
Below the rows is a multiply and divide step. Use it to scale one duration: a task that takes 12 minutes 30 seconds, repeated four times, or a recording split into equal parts. The multiplier or divisor is any number you type.
The result appears four ways at once. First is h:mm:ss for reading aloud. Then total minutes and total seconds, handy when a form or a spreadsheet wants a single unit. Last is decimal hours, which is what most time sheets and invoices expect.
Everything runs in your browser, and nothing you type is sent anywhere. That holds for long lists of rows and for quick one-line sums alike.
Worked examples
Questions about this calculator
Can I enter more than 59 minutes in a box?
Yes. Typing 90 in the minutes box is read as 1 hour 30 minutes, and the result is carried properly.
Can I divide by a number with decimals?
Yes. To find a third of a duration, divide by 3. To scale one up by half again, multiply by 1.5.
Why is there a decimal hours figure?
Pay rates and billing sheets use hours with a decimal part, such as 4.25. The page gives that value so you do not have to convert by hand.
Does it work for adding clock times like 2:30 PM?
This page adds lengths of time, not times of day. To get a finish time, use the time from now page or the clock-out calculator.