Time Duration Calculator — Hours Between Two Times, Free
Quick answer: A time duration calculator finds the elapsed time between two clock times. For example, 9:00 AM to 5:00 PM is 8 hours. Enter your start and end times above — overnight shifts (like 10:00 PM to 6:00 AM) are handled automatically.
What Is a Time Duration Calculator?
A time duration calculator measures the elapsed time between two points in time. Type in a start time and an end time, and it tells you how many hours and minutes passed — for example, 9:15 AM to 5:45 PM is 8 hours 30 minutes. It is the fastest way to total work hours, shift lengths, sleep time, travel durations, or any span where doing the math by hand risks an error.
How to Calculate Time Duration Manually (5 Steps)
- Convert both times to 24-hour format. 2:30 PM becomes 14:30; 12:00 AM (midnight) becomes 00:00.
- Convert each time to minutes since midnight. Multiply hours by 60 and add minutes: 14:30 → (14 × 60) + 30 = 870 minutes.
- Subtract start from end. 870 − 555 (9:15 AM) = 315 minutes.
- If the result is negative, add 1,440 (the number of minutes in a day). A negative result means the shift crossed midnight.
- Subtract any unpaid breaks, then split back into hours and minutes. 315 minutes = 5 hours 15 minutes.
Worked Examples: Common Shifts
| Shift | Break | Duration | Decimal hours |
|---|---|---|---|
| 9:00 AM – 5:00 PM | None | 8h 00m | 8.00 |
| 9:15 AM – 5:45 PM | None | 8h 30m | 8.50 |
| 8:30 AM – 4:45 PM | 30 min | 7h 45m | 7.75 |
| 9:00 AM – 5:45 PM | 45 min | 8h 00m | 8.00 |
| 10:00 PM – 6:00 AM | None | 8h 00m (overnight) | 8.00 |
| 11:30 PM – 1:15 AM | None | 1h 45m (overnight) | 1.75 |
Decimal Hours vs Hours-and-Minutes — Don’t Mix Them Up
This is the #1 timesheet mistake: 8 hours 30 minutes is 8.5 hours, not 8.30. Minutes are sixtieths of an hour, not hundredths. Typing 8.30 into payroll software pays you for 8 hours 18 minutes — you lose 12 minutes of pay every shift.
| What you worked | Type this (correct) | Not this (wrong) |
|---|---|---|
| 8h 15m | 8.25 | 8.15 |
| 8h 30m | 8.50 | 8.30 |
| 8h 45m | 8.75 | 8.45 |
| 7h 20m | 7.33 | 7.20 |
Minutes to Decimal Hours — Conversion Table
Formula: decimal hours = hours + (minutes ÷ 60).
| Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|
| 5 min | 0.08 | 35 min | 0.58 |
| 10 min | 0.17 | 40 min | 0.67 |
| 15 min | 0.25 | 45 min | 0.75 |
| 20 min | 0.33 | 50 min | 0.83 |
| 25 min | 0.42 | 55 min | 0.92 |
| 30 min | 0.50 | 60 min | 1.00 |
How Overnight Shifts Work
When the end time is earlier than the start time, the calculator treats the end as the next day. The mental method: count to midnight, then onward. Example: 11:30 PM → 1:15 AM. From 11:30 PM to midnight is 30 minutes; midnight to 1:15 AM is 1 hour 15 minutes; total = 1 hour 45 minutes.
Should You Subtract Your Lunch Break?
Yes — subtract unpaid breaks to get net work time. Gross time is the full span (9:00 AM–5:00 PM = 8h); net time subtracts the unpaid lunch (minus 30 min = 7.5h). Paid breaks (usually 10–15 minutes) stay in. In the US, the Fair Labor Standards Act does not require breaks, but when an employer offers a meal period of 30+ minutes duty-free, it is unpaid.
12-Hour vs 24-Hour (Military) Time
12 AM is midnight; 12 PM is noon — the most confused pair in time math. To convert PM times, add 12 (3:00 PM = 15:00). Midnight (12:00 AM) becomes 00:00. The 24-hour clock is standard in healthcare, aviation, the military, and most countries outside the US.
| 12-hour | 24-hour | 12-hour | 24-hour |
|---|---|---|---|
| 12:00 AM (midnight) | 00:00 | 12:00 PM (noon) | 12:00 |
| 1:00 AM | 01:00 | 1:00 PM | 13:00 |
| 6:00 AM | 06:00 | 6:00 PM | 18:00 |
| 11:00 AM | 11:00 | 11:00 PM | 23:00 |
Calculating Hours in Excel and Google Sheets
Put the start time in A2 and end time in B2. For decimal hours: =(B2-A2)*24. For hh:mm display: =TEXT(B2-A2,”h:mm”). For overnight shifts where the end is earlier than the start: =MOD(B2-A2,1)*24.
Time Zones and Daylight Saving
Convert both times to UTC before subtracting when zones differ. Daylight saving can change a shift’s real length: on spring-forward night the clock jumps ahead one hour, so an 8-hour overnight shift is only 7 real hours; on fall-back night it is 9.
Time Duration for Payroll and Invoicing
Payroll software (QuickBooks, Gusto) imports decimal hours, not hh:mm. For billable work, round to standard increments: 6-minute (0.1h) increments are the legal-industry standard; 15-minute increments are common at agencies. Always round in the client’s favor or per your contract — and disclose the rule on the invoice.
Common Uses
- Work hours & overtime — daily totals feed the 40-hour FLSA overtime week
- Sleep tracking — 11:00 PM to 6:30 AM = 7.5 hours of sleep
- Travel — flight and drive durations across time zones
- Meetings & events — agenda blocks that add up correctly
- Study & project sessions — focused-work totals
- Cooking — marinade, proofing, and slow-cook spans
Frequently Asked Questions
How do I calculate the hours between two times?
Convert both times to minutes since midnight (hours × 60 + minutes), subtract the start from the end, and if the result is negative add 1,440 (minutes per day) for overnight spans. Divide by 60 for hours. Example: 9:15 AM (555 min) to 5:45 PM (1,065 min) = 510 minutes = 8 hours 30 minutes.
How many hours is 9:15 AM to 5:45 PM?
8 hours 30 minutes (8.5 decimal hours). From 9:15 AM to 5:15 PM is 8 hours, plus 30 more minutes to 5:45 PM.
What if my shift ends after midnight?
Treat the end time as the next day: if end − start is negative, add 24 hours (1,440 minutes). Example: 10:00 PM to 6:00 AM = 8 hours.
Should I subtract my lunch break from my work hours?
Yes, subtract unpaid meal breaks (typically 30–60 minutes) to get net payable hours. Paid rest breaks (10–15 minutes) are not subtracted. 9:00 AM–5:00 PM with a 30-minute unpaid lunch = 7.5 hours.
Is 8 hours 30 minutes the same as 8.30 hours?
No — it is 8.5 hours. Minutes are sixtieths of an hour: 30 ÷ 60 = 0.5. Typing 8.30 into payroll software records only 8 hours 18 minutes, shorting you 12 minutes.
How do I convert minutes to decimal hours?
Divide minutes by 60 and add whole hours: decimal = hours + (minutes ÷ 60). Examples: 15 min = 0.25, 20 min ≈ 0.33, 45 min = 0.75. So 7h 45m = 7.75 hours.
How do I add hours and minutes together?
Add minutes first and carry every 60 into hours — a clock counts in sixties. Example: 2:45 + 1:20 = 3:65 → carry → 4:05. With seconds: 2:45:30 + 1:20:45 = 4:06:15.
What is the difference between a duration and a time of day?
A time of day is a point on the clock (3:00 PM); a duration is a length of time (3 hours). You can add durations together, but adding two times of day is meaningless.
Is 12 AM midnight or noon?
12 AM is midnight (00:00) and 12 PM is noon (12:00). Mnemonic: AM starts the day at midnight; the PM block starts at midday.
How do I calculate work hours in Excel?
With start in A2 and end in B2: decimal hours = (B2-A2)*24; hh:mm display = TEXT(B2-A2,”h:mm”); overnight-safe = MOD(B2-A2,1)*24. Format the result cell as a number, not a time.
How many hours did I sleep from 11 PM to 6:30 AM?
7.5 hours. 11:00 PM to midnight = 1 hour, plus 6.5 hours to 6:30 AM. Most adults need 7–9 hours (CDC), so 7.5 is in the healthy range.
Do daylight saving changes affect my shift length?
Yes. On spring-forward night the clock skips an hour, so an 8-hour overnight shift is only 7 real hours; on fall-back night it becomes 9. US employers generally pay by clock time per policy — check yours.