Time Duration Calculator

Calculate the hours and minutes between two times, including across midnight. Enter start and end, get the duration. No signup. Ideal for work hours, timesheets and scheduling.

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Duration
Total minutes
Total seconds

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This time duration calculator finds the hours and minutes between two times, including across midnight, directly in your browser. Enter a start time and an end time, and read the exact duration. No account, no install, so you can work out shift lengths, timesheets, or the gap between any two times on any device in seconds.

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How to Calculate Time Duration Step by Step
Why Calculating Time Duration Is Tricky
This Calculator Versus Doing the Maths by Hand
Who Needs a Time Duration Calculator
Pro Tips for Accurate Duration Calculations
Common Time Duration Mistakes to Avoid
Related Tools You May Need Next
Frequently Asked Questions

How to Calculate Time Duration Step by Step

Enter the start time. Type the starting time into the start field, such as the time a shift or activity began. Use the correct format, and note whether it is a morning or afternoon time.
Enter the end time. Type the ending time into the end field, such as when the shift or activity finished. The calculator will find the duration between the two times.
Read the duration. The calculator shows the exact time between the two, in hours and minutes, giving you the elapsed duration without any manual arithmetic.
Handle crossing midnight. If the end time is earlier in the clock than the start, the period crosses midnight. The calculator accounts for this, giving the correct duration rather than a negative one.
Use the result. Apply the duration to your timesheet, schedule, or calculation, knowing the elapsed time is accurate including any crossing of midnight.

Time duration calculator showing hours between two times

Why Calculating Time Duration Is Tricky

Calculating the time between two clock times sounds simple but is a common source of errors, because time is not measured in the base ten we do arithmetic in. There are sixty minutes in an hour, not a hundred, so subtracting times requires borrowing across this sixty boundary rather than the usual ten. This is why working out that the gap between two times is a certain number of hours and minutes trips people up.

The twelve hour clock, with its morning and afternoon designations, adds another layer of difficulty. Confusing a morning time with an afternoon one, or mishandling the switch at noon and midnight, leads to durations that are off by twelve hours. The twenty four hour clock avoids this ambiguity, but many people work with the twelve hour format, so getting the morning and afternoon right is essential for a correct duration.

Crossing midnight is the classic trap. When a period starts in the evening and ends in the morning, the end time is a smaller clock number than the start, and naive subtraction gives a wrong or negative result. The calculator recognises the period spans midnight and adds the correct hours automatically.

Crossing midnight is the classic trap in time duration calculations. When a period starts in the evening and ends in the early morning, the end time on the clock is a smaller number than the start time, and a naive subtraction gives a negative or nonsensical result. The correct calculation recognises that the period spans midnight and adds the appropriate hours, which a calculator handles automatically but people often get wrong by hand.

These calculations matter most for work hours and scheduling, where accuracy has real consequences. A timesheet that miscalculates a shift length affects pay. A schedule that misjudges a duration causes conflicts. Working out how long an activity, a journey, or a shift lasts is a frequent practical need, and getting it right, especially across midnight or with the twelve hour clock, is exactly what a duration calculator ensures.

This Calculator Versus Doing the Maths by Hand

Challenge	Why it causes errors	How the calculator helps
Base sixty minutes	Not base ten, needs borrowing across sixty	Handles the arithmetic correctly
Twelve hour clock	Morning and afternoon confusion	Accounts for the designation
Crossing midnight	End time smaller than start	Recognises the span and adds hours
Timesheet accuracy	Errors affect pay	Gives the exact duration

Who Needs a Time Duration Calculator

Workers filling timesheetsSomeone recording their hours calculates the exact duration of each shift, including any that cross midnight, for an accurate timesheet and correct pay.

Managers scheduling shiftsA manager works out shift lengths and coverage by calculating durations between start and end times, ensuring the schedule adds up correctly.

Freelancers billing by timeA freelancer billing clients by the hour calculates the exact duration worked between two times, so their invoices are accurate.

People planning activitiesSomeone planning a journey, an event, or an activity works out how long it lasts between a start and end time, for scheduling and coordination.

Anyone finding a time gapA person who needs to know the exact time between two clock times, for any reason, calculates it instantly rather than doing the awkward arithmetic.

Worker calculating shift hours for a timesheet

Pro Tips for Accurate Duration Calculations

Get the morning and afternoon right. On the twelve hour clock, confirm whether each time is morning or afternoon, since a mix up shifts the duration by twelve hours. The twenty four hour clock avoids this ambiguity entirely if you can use it.

Let the calculator handle crossing midnight. For a period that spans midnight, do not try to subtract by hand, which gives a wrong result. The calculator recognises the overnight span and gives the correct duration automatically.

Use for accurate timesheets. For work hours where accuracy affects pay, calculate each shift's duration precisely rather than estimating, especially for shifts crossing midnight, which are the easiest to get wrong.

Convert to decimal hours if billing. If you bill or record time in decimal hours rather than hours and minutes, note that thirty minutes is half an hour, and convert the minutes accordingly for your records.

Add up multiple durations for a total. For a total across several periods, calculate each duration and sum them. Remember to carry minutes over sixty into hours when adding, which is where manual totals often go wrong.

Check dates for very long durations. For a duration spanning more than a day, you also need the dates, not just the times. Our Date Difference Calculator handles gaps measured in days.

Common Time Duration Mistakes to Avoid

Mishandling the crossing of midnight. Subtracting an early morning end time from an evening start time naively gives a negative or wrong result. A period spanning midnight needs the overnight span accounted for, which the calculator does but manual subtraction often gets wrong.

Confusing morning and afternoon times. On the twelve hour clock, treating an afternoon time as a morning one, or vice versa, shifts the duration by twelve hours. Always confirm the correct designation for each time, or use the twenty four hour clock to avoid the ambiguity.

Doing base ten arithmetic on time. Time uses sixty minutes to an hour, not a hundred, so ordinary base ten subtraction gives wrong results. The borrowing must happen across sixty, which is why manual time arithmetic is error prone and a calculator is safer.

Forgetting to carry minutes when totalling. When adding several durations, minutes over sixty must be carried into hours. Forgetting this leaves a total with more than sixty minutes shown, which is incorrect. The carry across sixty is where manual totals commonly fail.

For durations measured in days rather than hours, our Date Difference Calculator finds the gap between dates. To count down to a time, the Countdown Timer helps, and the Age Calculator works out durations in years.

Duration result including a period across midnight

Frequently Asked Questions

How do I calculate the duration between two times?

Enter the start time and the end time, and the calculator shows the exact duration between them in hours and minutes. It handles the awkward parts automatically, including the base sixty arithmetic of minutes and periods that cross midnight. This gives you an accurate elapsed time without the manual calculation that so often goes wrong, making it ideal for shift lengths, timesheets and any gap between two clock times.

How do I calculate hours across midnight?

Simply enter the start time, such as an evening time, and the end time, such as an early morning time, and the calculator recognises that the period spans midnight and gives the correct duration. This is where manual calculation commonly fails, because naively subtracting an early morning end time from an evening start time gives a negative or nonsensical result. The calculator accounts for the overnight span automatically.

Why is calculating time duration so error prone by hand?

Because time is not measured in base ten. There are sixty minutes in an hour, so subtracting times requires borrowing across sixty rather than the usual ten, which trips people up. The twelve hour clock adds morning and afternoon confusion, and periods crossing midnight cause negative results from naive subtraction. These factors together make manual time arithmetic surprisingly error prone, which is why a calculator is more reliable.

Can it calculate work hours for a timesheet?

Yes, this is a common use. Enter the start and end times of a shift and the calculator gives the exact duration, including for shifts that cross midnight, which are the easiest to miscalculate. Accurate durations matter for timesheets because errors affect pay. For a total across several shifts, calculate each duration and add them, carrying minutes over sixty into hours, which is another step where manual totals often go wrong.

What about the twelve hour versus twenty four hour clock?

The twelve hour clock uses morning and afternoon designations, and confusing them shifts a duration by twelve hours, a frequent error. The twenty four hour clock avoids this ambiguity by numbering hours from zero to twenty three, so there is no morning or afternoon confusion. If you can work in the twenty four hour format, it reduces mistakes; otherwise, always confirm the correct designation for each time you enter.

How do I add up several durations?

Calculate each individual duration between its start and end times, then add them together, remembering to carry any minutes over sixty into the hours, since sixty minutes make one hour. This carry across sixty is where manual totals commonly go wrong, producing a result with more than sixty minutes shown. Adding durations carefully with the correct carrying gives an accurate total across multiple periods, such as several shifts in a week.

Can it calculate durations longer than a day?

This calculator works with clock times within and across a single midnight, giving hours and minutes. For durations spanning multiple days, you also need the dates involved, not just the times, since the number of days matters. For gaps measured in days, weeks or months between two dates, a date difference calculator is the right tool, as it accounts for the full calendar span rather than just clock times.

Is the time duration calculator free?

Yes, it is completely free with no account and no usage limit. You can calculate the duration between as many pairs of times as you like, as often as you like, at no cost. It runs entirely in your browser on any device, so there is nothing to download or install, and the exact duration in hours and minutes appears instantly whenever you enter a start and end time.