Time does not add like ordinary numbers: 50 minutes plus 20 minutes is 1 hour 10 minutes, not 70 “something”. This time calculator handles the base-60 carrying for you. Add or subtract two durations, multiply a duration by a number, divide it into equal parts, or find how many times one duration fits into another.
How to use the time calculator
- Choose the operation: add, subtract, multiply, divide, or “how many times B fits in A”.
- Enter duration A in days, hours, minutes and seconds. Leave unused boxes at 0.
- Enter duration B, or the number to multiply or divide by.
- Read the result on the tape in words, in clock format (h:mm:ss) and as totals in days, hours, minutes and seconds.
How time arithmetic works
Every duration is converted to a single unit, seconds, so the math is ordinary arithmetic:
After adding, subtracting, multiplying or dividing, the total is split back into units by repeated division with remainders:
| Unit | Seconds | Minutes | Hours |
|---|---|---|---|
| 1 minute | 60 | 1 | 0.01667 |
| 1 hour | 3,600 | 60 | 1 |
| 1 day | 86,400 | 1,440 | 24 |
| 1 week | 604,800 | 10,080 | 168 |
Worked examples
Add: 2 h 45 min 30 s + 1 h 30 min 50 s. In seconds that is 9,930 + 5,450 = 15,380 s. Split back: 15,380 ÷ 3,600 = 4 hours with 980 s left, 980 ÷ 60 = 16 minutes with 20 s left, giving 4 hours 16 minutes 20 seconds (4:16:20).
Multiply: a 1 h 12 min 30 s bike lap ridden 4 times is 4,350 × 4 = 17,400 s = 4 hours 50 minutes.
Divide: 1 day shared by 4 people is 86,400 ÷ 4 = 21,600 s = 6 hours each.
How many times: 2:45:30 ÷ 1:30:50 = 9,930 ÷ 5,450 = 1.822, so B fits once with 1 hour 14 minutes 40 seconds left over.
Doing it by hand: carrying and borrowing
When adding on paper, add each column separately and then carry from right to left:
- 30 s + 50 s = 80 s → write 20 s, carry 1 minute.
- 45 min + 30 min + 1 = 76 min → write 16 min, carry 1 hour.
- 2 h + 1 h + 1 = 4 h.
When subtracting, borrow 60 instead of 10. For 3:10 − 1:45, borrow an hour: 2:70 − 1:45 = 1:25.
Common mistakes
- Treating minutes as decimals. 1:30 is 1.5 hours, not 1.3. Use the decimal-hours total on the tape when you need to multiply by an hourly rate, or the time to decimal hours calculator.
- Mixing clock times and durations. 9:00 AM + 8 hours is a clock time (5:00 PM). For that question, use the add time to a clock time calculator; for the gap between two clock times, the time duration calculator.
- Adding a long list. For a column of h:mm entries, such as a week of timesheet hours, the hours and minutes calculator accepts the whole list at once.
Frequently asked questions
How do I add hours and minutes together?
Add the seconds, minutes and hours separately, then carry: every 60 seconds becomes a minute and every 60 minutes an hour. 2:45:30 + 1:30:50 gives 3:75:80, which carries to 4:16:20.
How do I divide a time by a number?
Convert the time to seconds, divide, and convert back. One day split into 4 equal shifts is 86,400 ÷ 4 = 21,600 seconds, or 6 hours each.
Can a result be negative?
Yes. When you subtract a longer duration from a shorter one, the result is shown with a minus sign, for example 1:00:00 − 1:30:00 = −30 minutes.
Can I enter decimals such as 1.5 hours?
Yes. Every box accepts decimals, so 1.5 hours is the same as 1 hour 30 minutes. Results keep fractions of a second to the millisecond.