Time Duration Calculator

Welcome to our official time duration calculator. Whether you need to figure out how many hours you worked on a shift, or you simply need to calculate time between two times for a personal project, handling the math manually can lead to frustrating errors. Our tool instantly determines the exact elapsed duration, saving you from complex mental math.

Infographic showing a timeline calculating the elapsed time duration between 9 AM and 5 PM

Visual representation of measuring elapsed time between a start and end point.

How to calculate time duration between two times

If you don't have our calculator handy, performing the math yourself requires converting standard AM/PM clock readings into a 24-hour military time format. This prevents negative numbers when subtracting the afternoon from the morning. If you need help with this conversion, use our Military Time Converter.

Step-by-step elapsed time formula

Convert to 24-hour format: For example, 2:00 PM becomes 14:00.
Subtract Start from End: Subtract the starting minutes from the ending minutes, and the starting hours from the ending hours.
Adjust for minute borrowing: If your minute result is negative, borrow 60 minutes from the hour column.

**Example: Calculating shift duration from 9:15 AM to 5:00 PM**
Step	Action Performed	Result
1. Format	Convert 5:00 PM to 24-hour time	17:00
2. Subtract	17:00 minus 09:15 (Requires borrowing an hour)	16:60 - 09:15
3. Final Math	16 - 9 hours, and 60 - 15 minutes	7 Hours 45 Mins

How to handle overnight time duration calculations

The most common pain point when trying to calculate elapsed time is dealing with graveyard or overnight shifts. When your End Time occurs the next day, standard subtraction breaks down because the end number is technically smaller than the start number.

Graphic illustrating how to calculate an overnight shift duration crossing midnight from 10 PM to 2 AM

To calculate overnight shifts, you must mathematically add 24 hours to the end time.

To solve this manually, if your end time is "smaller" than your start time, simply add 24 hours to the end time before doing the math. For example, a shift from 10:00 PM (22:00) to 2:00 AM (02:00) becomes: (02:00 + 24:00) - 22:00 = 4 hours of duration.

Understanding the decimal hours format

Notice that our calculator outputs two results: standard hours/minutes, and "decimal hours." Why is this important? Because payroll systems cannot multiply standard minutes (base-60) by a monetary hourly wage (base-10).

Before calculating your gross pay, your elapsed time must be converted. You can learn more on our dedicated Decimal Time Calculator page, or use the quick reference chart below:

Standard Minutes	Mathematical Formula	Decimal Equivalent
15 Minutes	15 ÷ 60	.25 Hours
30 Minutes	30 ÷ 60	.50 Hours
45 Minutes	45 ÷ 60	.75 Hours

Frequently Asked Questions

How do I calculate the time duration between two times?

To calculate duration manually, convert both times to a 24-hour format. Then, subtract the Start Time from the End Time. If the End Time is numerically smaller (indicating an overnight span), add 24 hours to it before subtracting.

Does this time duration calculator handle overnight shifts?

Yes. If your Start Time is 10:00 PM and End Time is 2:00 AM, our tool automatically recognizes this crosses midnight and correctly outputs an overnight duration of 4 hours.

Why do I need to calculate elapsed time in decimals?

Payroll systems cannot multiply standard minutes by an hourly wage. Elapsed time must be converted into decimals (e.g., 30 minutes equals 0.5 hours) so employers can accurately calculate your gross pay.

Is military time required for this calculator?

No. Our calculator features smart input detection. You can enter standard 12-hour AM/PM formats, shorthand (like '9a' or '5p'), or standard 24-hour military time, and it will process the duration seamlessly.