Time Duration Calculator (Add & Subtract HH:MM:SS)
Add, subtract, multiply and divide durations in HH:MM:SS, MM:SS or units like 1d 2h 30m, one per line or as one expression, with a live total.
2:00:30
A list of durations, added and subtracted
Paste or type a list of time durations — one per line — and this calculator adds them together and shows the running total in HH:MM:SS. Each line can be written as HH:MM:SS (for example 1:30:00), as MM:SS (for example 45:30) or in units — d, h, m, s and ms, the words spelled out, or 일, 시간, 분 and 초 — so a fortnight is simply 14d, and you can put a leading + or − in front of any line to add or subtract it. Any field or amount may carry a decimal, and one line can hold a whole expression with + − × ÷ and brackets, such as (1h + 30m) / 3 or 45:00 × 12; when the only line divides one time by another, the answer is a plain number — how many times the second fits into the first. That makes it easy to answer questions like "how long were these five video clips altogether?" or "if I remove a 15-minute break from a 2-hour session, what's left?". The total updates the instant you type, and secondary lines show the same result as a plain number of seconds, of hours and of minutes, so you can copy whichever form you need. Give a start time and the page says the clock time the total ends at — the same day, the next day, or so many days later or earlier. Every day is counted as the same length, so a daylight-saving change is not taken into account. Copy link hands the list to someone else — it opens on the same list and total — without the list ever sitting in the address bar (for a list too long for a link, the page says so instead), and Clear empties the box in one click.
How the totals are calculated
Every line is converted to a signed number of seconds: hours are multiplied by 3600, minutes by 60, and seconds are added as-is, with a leading − flipping the whole line negative. The tool then sums all the lines. Field overflow is allowed, so 90:00 is read as 90 minutes (5400 seconds) rather than being rejected — handy when your source data isn't normalized. Blank lines and anything that can't be parsed are skipped and counted so you can spot typos.
Time units
- 1 week = 7 days = 168 hours = 10,080 minutes = 604,800 seconds
- 1 day = 24 hours = 1,440 minutes = 86,400 seconds
- 1 hour = 60 minutes = 3,600 seconds
- 1 minute = 60 seconds
- 1 second = 1,000 milliseconds
Days, hours, minutes, seconds and milliseconds can be typed here as they are (d, h, m, s, ms); weeks cannot, so turn them into days first — 2 weeks is 14d.
Frequently asked questions
How do I subtract a duration instead of adding it?
Put a minus sign in front of the line. For example, a list of 1:00:00 and -0:30:00 totals 0:30:00, because the second line is subtracted. A leading + is optional and simply means add.
What time formats are accepted?
Each line can be HH:MM:SS (like 2:05:30), MM:SS (like 45:30) or units such as 1d 2h 3m 4s, 1.5h or 1일 2시간, optionally starting with + or −, and any field may carry a decimal. Fields may overflow, so 90:00 is treated as 90 minutes. Lines that don't match are ignored and reported so you can fix them.
Can I multiply or divide a duration?
Yes. A line can be a whole expression with + − × ÷ (or * and /) and brackets: 45:00 × 12 is twelve 45-minute sessions, 10h ÷ 4 splits a shift four ways, and (1h + 30m) / 3 works too. A time can be multiplied or divided by a plain number, but not multiplied by another time. When the only line divides a time by a time — 10h / 25m — the answer is a plain number: how many times the second fits into the first.
Can I send the list and its total to someone?
Yes. Copy link hands over a link that opens on the same list and the same total, while the list itself never sits in the address bar. A list too long to travel safely in a link gets a sentence saying so instead of a link a chat app would cut short.
Can I type weeks?
Not as a unit — the units are d, h, m, s and ms, the same words spelled out, and 일, 시간, 분 and 초. Write weeks as days instead: two weeks is 14d, and a week and a half is 10.5d, since any amount may carry a decimal. The “Time units” list in the text below the tool shows how a week, a day, an hour and a minute break down.