How to Calculate Time Duration: Between Two Times, and Adding Shifts and Breaks

To calculate a time duration, subtract the start from the end and borrow in sixties, not tens: 09:15 to 17:45 is 8 hours 30 minutes, and a night shift from 22:40 to 06:15 is 7 hours 35 minutes. Adding durations works the same way — 2 hours 45 minutes plus 1 hour 50 minutes is 4 hours 35 minutes. The Time Duration Calculator handles the borrowing, midnight and totals; this guide shows the method.

Duration arithmetic is where confident people make quiet errors, because time refuses to behave like decimal numbers. Minutes borrow and carry at 60, days turn over at 24, and the clock shows 06:15 both before and after a night shift. Those errors land in places that matter: payroll runs on durations, project estimates are durations wearing a costume, and care rotas, rental charges and billing all total durations across days and people. A half-hour slip repeated across a team's timesheets is real money in one direction or a real grievance in the other, and it almost always traces back to someone adding clock times as if they were decimals — 2.45 plus 1.50 making 3.95, a number that looks tidy and is wrong.

How to Calculate Time Duration Online, Step by Step

1. Open the calculator. Go to the Time Duration Calculator with the start and end times in front of you.
2. Enter start and end exactly as recorded. Use the 24-hour clock where you can — 17:45 cannot be confused with 5:45 in the morning; if your records are 12-hour, settle AM and PM before calculating, not after.
3. Mark next-day ends honestly. A shift ending at 06:15 after a 22:40 start ends tomorrow. The calculator's day handling does the midnight split for you.
4. Subtract breaks per shift. Enter or deduct the unpaid break on the same line as its shift, so the weekly total is auditable shift by shift.
5. Total in clock form, convert at the end. Add durations as hours and minutes; turn the final total into decimal hours only when payroll or billing needs it.

The Borrowing Method, Worked in Full

Subtract minutes first, then hours. From 09:15 to 17:45 the minutes subtract cleanly: 45 − 15 = 30, and the hours give 17 − 9 = 8, so 8 hours 30 minutes. When the end minutes are smaller, borrow one hour as 60 minutes: from 09:45 to 17:15, the minutes cannot do 15 − 45, so borrow — 75 − 45 = 30 minutes, and the hours become 16 − 9 = 7, giving 7 hours 30 minutes. The night shift splits at midnight: 22:40 to 24:00 is 1 hour 20 minutes, 00:00 to 06:15 is 6 hours 15 minutes, total 7 hours 35 minutes. Addition mirrors subtraction with carrying instead of borrowing: 2:45 + 1:50 stacks to 3 hours and 95 minutes, and 95 minutes carries to 1 hour 35, closing at 4 hours 35 minutes. Every duration task — elapsed time, totals, end-time problems such as 09:15 plus 6 hours 20 minutes landing at 15:35 — is one of these two moves.

Task	Working	Duration
Day shift 09:15 → 17:45	45−15 = 30 min; 17−9 = 8 h	8 h 30 min
Night shift 22:40 → 06:15	1 h 20 min to midnight + 6 h 15 min after	7 h 35 min
Two tasks 2 h 45 + 1 h 50	3 h 95 min, carry 60	4 h 35 min
Five day shifts	5 x 8 h 30 min	42 h 30 min
Same week, 30-min daily break removed	42 h 30 min − 2 h 30 min	40 h 00 min

Durations at Work: Payroll, Projects and Estimates

Payroll converts the weekly total to a decimal exactly once: 42 hours 30 minutes is 42.5 hours; at any hourly rate, that decimal is what multiplies. Project work runs the other direction — an estimate in minutes becomes a calendar promise: 10,000 minutes is 166 hours 40 minutes, which at 8 working hours a day is not "about three weeks" but 20 full days plus 6 hours 40 minutes, as one of the FAQs below works through in full. For single unit hops — hours to minutes, days to hours — our time converter and the guide to converting time units cover the factors; for spans between calendar dates rather than clock times, the date difference calculator takes over, since months refuse to be a fixed number of days.

Five Mistakes That Spoil Duration Calculations

• Adding times as decimals. 2.45 + 1.50 = 3.95 is spreadsheet thinking applied to a sixty-based system. The true total is 4 hours 35 minutes.
• Forgetting the night shift ends tomorrow. An end earlier than the start means midnight was crossed, not that the shift lasted negative hours.
• Wrapping at 24 hours. Clock-formatted cells display a 30-hour total as 6 hours. Totals need elapsed-time formatting or a duration tool.
• Rounding every shift, then totalling. Rounding five shifts up by six minutes invents half an hour a week. Total exact durations; round once, at the end, by a stated rule.
• Recording breaks nowhere. A total nobody can audit becomes an argument nobody can settle. Breaks belong on the shift's own line.

Conclusion: Borrow in Sixties, Total Honestly

Duration maths is decimal maths with one changed rule — carry and borrow at sixty — plus the discipline of marking midnight crossings and breaks where they happen. Follow that, and timesheets, estimates and rotas agree with each other; skip it, and they drift apart a few minutes at a time. Let the Time Duration Calculator do the borrowing when the list gets long.

From Clock Form to Decimal Hours: The Payroll Table

When a duration leaves the timesheet and enters payroll or billing, it changes clothes: minutes become decimal fractions of an hour by dividing by 60. The conversions below cover this guide's own worked examples, and they are worth pinning beside any manual timesheet. 8 hours 30 minutes becomes 8.5 hours exactly, which is why half-hour shifts price so cleanly. 7 hours 35 minutes — the night shift — becomes about 7.58 hours (35 divided by 60 is 0.583), and 4 hours 35 minutes becomes about 4.58 hours by the same step. The weekly total of 42 hours 30 minutes becomes 42.5 hours. Notice that only the round half-hours land on tidy decimals; every other duration produces a repeating or rounded decimal, which is exactly why the clock form stays on the record and the decimal is produced once, at the pay step, from the exact total.

Frequently Asked Questions

How do you calculate the duration between two times?

Subtract the start from the end, borrowing an hour as 60 minutes when the end minutes are smaller. From 09:15 to 17:45: 45 minus 15 is 30 minutes, 17 minus 9 is 8 hours — 8 hours 30 minutes. The calculator does the borrowing for you, including across midnight.

How do you calculate a shift that crosses midnight?

Split it at midnight. From 22:40 to 24:00 is 1 hour 20 minutes, and from 00:00 to 06:15 is 6 hours 15 minutes; together that is 7 hours 35 minutes. Treating the end time as smaller than the start, instead of next-day, is the error that makes night shifts come out negative.

How do you add two durations together?

Add the minutes and hours separately, then carry every 60 minutes into an hour. 2 hours 45 minutes plus 1 hour 50 minutes gives 3 hours 95 minutes, and 95 minutes is 1 hour 35, so the total is 4 hours 35 minutes — decimal addition would wrongly give 3.95 hours.

How do you turn hours and minutes into a decimal for payroll?

Divide the minutes by 60 and add them to the hours: 8 hours 30 minutes is 8 + 30/60 = 8.5 hours. Payroll systems multiply decimal hours by the rate, while timesheets record the clock form — keep both, and convert only at the pay step so the record stays human-readable.

Should breaks be subtracted before or after totalling?

Either way gives the same total, but subtracting per shift is easier to audit: the record shows the shift, the break and the paid duration side by side. A week of five 8 hour 30 minute shifts with a 30-minute daily break is five shifts of 8 hours — 40 paid hours, not 42.5 minus a vague lump.

How long is 10,000 minutes in days and hours?

Divide by 60 for hours (166 hours, remainder 40 minutes), then by 24 for days: 6 days, 22 hours and 40 minutes. The calculator chains these conversions so a project estimate in minutes becomes a calendar answer without manual remainders.

Why does my spreadsheet give a different duration?

Spreadsheets store times as fractions of a day, and a result formatted as a clock time wraps every 24 hours — a 30-hour duration displays as 6 hours. Format the result as elapsed time (or total hours) rather than a time of day, or use the duration calculator, which never wraps.