Time
Time Duration Calculator
Enter two clock times and get the duration between them — in hours and minutes, decimal hours, and total minutes. Overnight spans are handled automatically, and you can subtract a break. Results update live, with the working shown.
Clock
Enter two times
Duration
8h 30m
9:00 AM → 5:30 PM
8.50 decimal hours(8h 30m)
Decimal hours
8.50
Hrs : min
8h 30m
Total minutes
510
Try an example
No sign-up · Free
The basics
What is a time duration?
A time duration is the length of the gap between two clock times — how long passed from a start to an end. It has nothing to do with the current time; it is a fixed span you read off the clock, the way you would measure a shift, a class, a flight, or how long the roast needs to stay in the oven.
duration = end − start
A span, not a moment
Subtract the start from the end. The result is a length of time, so it is measured in hours and minutes — never in a clock reading like “half past five.”
5:30 PM − 9:00 AM = 8h 30m
8h 30m = 8.5 h
Two ways to write it
The same span reads as hours and minutes for people and as decimal hours for payroll. Both describe one duration; only the notation differs.
510 minutes = 8h 30m = 8.50 h
Method
How to calculate it by hand
Four steps take you from two clock readings to a clean duration — and they are exactly what the tool shows under “Step by step.”
- 1
Convert each time to minutes since midnight
Multiply the hour by 60 and add the minutes. Use 24-hour values so PM times don’t trip you up — 5:30 PM is 17:30, which is 17 × 60 + 30.
9:00 AM = 540 · 5:30 PM = 1050 - 2
Subtract the start from the end
Take the start’s minutes away from the end’s. A positive result is your raw span in minutes.
1050 − 540 = 510 min - 3
If the answer is negative, add a day
A negative number means the end is on the next day (it crossed midnight). Add 1440 minutes — a full day — to bring it positive.
e.g. (420 + 1440) − 1380 = 480 min - 4
Split into hours and minutes
Divide by 60 for whole hours; the remainder is the minutes. Divide the whole span by 60 again for decimal hours.
510 ÷ 60 = 8h 30m = 8.5 h
Worked examples
See it across cases
The same subtraction handles a normal day, a shift that crosses midnight, and a day with a lunch break — only the wrap and the break change.
A morning start to an evening finish on the same calendar day — the end is later than the start, so you simply subtract.
Given: 9:00 AM → 5:30 PM
To minutes: 9:00 AM = 540 · 5:30 PM = 1050
Subtract: 1050 − 540 = 510 min
8h 30m= 8.50 decimal hours= 510 minutes
Crossing midnight
Handling overnight spans
The one place plain subtraction breaks down is when the end time reads earlier than the start. The clock has wrapped past midnight, and the fix is a single extra day.
end < start → +1440
Why a negative answer appears
If you subtract directly, an end that looks earlier than the start gives a negative number, because the clock reset to zero at midnight in between.
7:00 AM − 11:00 PM = −960 (wrong)
(end + 1440) − start
Add a full day to fix it
Adding 1440 minutes puts the end on the next day, where it belongs, and the subtraction comes out right. The tool spots the wrap and shows a “crosses midnight” note.
(420 + 1440) − 1380 = 480 = 8h
For payroll
Decimal hours, explained
Decimal hours are the format payroll, invoicing, and timesheet software expect — because you can multiply them straight by an hourly rate. The trick is converting the minutes part, not sticking it after the decimal point.
min ÷ 60
Convert the minutes
The minutes part becomes a fraction of an hour. A quarter hour is a quarter of one — the same logic for any number of minutes.
don’t paste the minutes
The classic trap
Writing the minutes after the decimal — treating half-past as point-three-zero — overstates or understates the pay. Always convert first.
hours × rate
Then multiply by the rate
Once the span is in decimal hours, pay is a single multiplication. That is the whole reason the format exists.
| Minutes | Fraction | Decimal |
|---|---|---|
| 15 min | quarter hour | 0.25 |
| 20 min | third of an hour | 0.33 |
| 30 min | half hour | 0.50 |
| 45 min | three-quarter hour | 0.75 |
Quick reference
Common shift durations
The lengths of the shifts people look up most — in hours and minutes and in decimal hours — including a few that cross midnight. Read off “how long is a 9 to 5?” or “how many hours is 11pm to 7am?” at a glance.
| Shift | From → to | Hrs : min | Decimal |
|---|---|---|---|
| 9 to 5 | 9:00 AM → 5:00 PM | 8h | 8.00 |
| 9 to 5:30 | 9:00 AM → 5:30 PM | 8h 30m | 8.50 |
| 8 to 4 | 8:00 AM → 4:00 PM | 8h | 8.00 |
| 8 to 5 | 8:00 AM → 5:00 PM | 9h | 9.00 |
| Half day (4h) | 9:00 AM → 1:00 PM | 4h | 4.00 |
| Night, 11pm–7am | 11:00 PM → 7:00 AM | 8h | 8.00 |
| Swing, 3pm–11pm | 3:00 PM → 11:00 PM | 8h | 8.00 |
| Double, 6am–6pm | 6:00 AM → 6:00 PM | 12h | 12.00 |
Where it shows up
When you reach for this
Any time you need the gap between two clock readings, not the time of day itself.
shifts & timesheets
Work hours
Clock-in to clock-out, minus a lunch, gives the hours to log. For a whole week of these, the time card tool adds them up.
study & cooking
Planned spans
How long a revision block, a recipe, or a meeting runs — fixed durations you set, with no dependence on the current time.
travel & sleep
Overnight gaps
Flights, train journeys, and a night’s sleep all cross midnight, where the add-a-day rule earns its keep.
Worth knowing
Common mistakes
Four slips account for almost every wrong duration — all easy to avoid once you see them.
1:00 PM = 13:00
Mishandling AM/PM
The biggest trap is reading PM hours as their small number. Convert to 24-hour first, or switch the tool to 24-hour mode, and the ambiguity disappears.
noon ≠ midnight
12 AM vs 12 PM
12:00 AM is midnight (00:00) and 12:00 PM is noon (12:00) — they are twelve hours apart. Getting them backwards flips a whole half-day.
end < start → +1 day
Forgetting the midnight wrap
An overnight span subtracts to a negative number. If your answer comes out negative, you forgot to add the day.
8h 30m ≠ 8.30 h
Faking decimal hours
The minutes are not the digits after the decimal point. Thirty minutes is 0.5 hours, not 0.30 — convert by dividing by 60.
More time tools
Pick the right one
This calculator is the simple two-times-between tool. For richer needs, the rest of the time set has you covered.
pay & rounding
Hours Calculator
The hours calculator adds a pay rate and quarter-hour rounding on top of the same span math.
a whole week
Time Card Calculator
The time card calculator totals a week of clock-in and clock-out rows, breaks and all.
years not hours
Age Calculator
For the span between two dates instead of two times, the age calculator gives years, months, and days.
FAQ
Common questions
Turn each time into minutes since midnight, then subtract the start from the end. For example 9:00 AM is 540 minutes and 5:30 PM is 1050 minutes, so the duration is 1050 − 540 = 510 minutes, which is 8 hours and 30 minutes. If the end time is earlier than the start, add 1440 minutes (a full day) before subtracting to handle the overnight wrap.
When the end time looks earlier than the start — say 11:00 PM to 7:00 AM — the span has crossed midnight, so add a full day to the end before subtracting. That is (420 + 1440) − 1380 = 480 minutes, or exactly 8 hours. The calculator detects this automatically and adds the day for you.
8 hours 30 minutes is 8.5 decimal hours. To convert any minutes part to a decimal, divide it by 60: 30 ÷ 60 = 0.5. So 45 minutes is 0.75 hours and 15 minutes is 0.25 hours. Decimal hours are what payroll and billing systems expect, because you multiply them straight by an hourly rate.
Because you can multiply decimal hours directly by a pay rate. 8 hours 30 minutes times $20 is not 8.30 × 20 — you must first convert the 30 minutes to 0.5, giving 8.5 hours, then 8.5 × $20 = $170. Working in decimal hours removes that conversion trap, which is why timesheets and billing software store time that way.
No. It works purely on the two times you type in, so the result never changes based on when you load the page. Enter any start and end time and you get the fixed span between them — ideal for shifts, study sessions, cooking times, or any planned duration.
Yes. Tick "Subtract a break / lunch" and enter the break in minutes. The break is taken off the raw clock-to-clock span, so a 9:00 AM to 5:30 PM day (8h 30m) with a 30-minute lunch becomes 8 hours of worked time. The break can never push the result below zero — it is capped at the length of the span.
This tool is the simplest one-pair version: two clock times in, the duration out, with an optional break. If you want pay-rate totals and quarter-hour rounding, use the Hours Calculator; to add up a whole week of clock-in and clock-out times, use the Time Card Calculator.
The classic mistake is forgetting that PM hours run from 12 to 23 in 24-hour terms: 1:00 PM is 13:00, not 1:00. And 12:00 PM is noon (12:00) while 12:00 AM is midnight (00:00). Convert both times to a 24-hour value first and the subtraction becomes simple. Switching the calculator to 24-hour mode sidesteps the ambiguity entirely.
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Written by
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Author
Ugo CharlesBuilt and fact-checked against our editorial standards · Last updated June 2026
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