Time Calculator - Add, Subtract & Calculate Duration Between Times
⏱️ Productivity Tool

Time Calculator & Clock Math

The easiest way to calculate time intervals. Find the duration between two clock times or determine a future time by adding hours and minutes.

Time Engine

Select calculation mode below.

🎛️ I want to...
▶️ Start Time
⏹️ End Time
TOTAL DURATION
8h 30m
Within same day
🔢
Decimal Hours 8.50 hrs
⏱️
Total Minutes 510 min

How to Calculate Time Differences

Calculating time isn't as simple as normal math because time is based on 60 (base-60 system), not 100. Here is how our tool handles it.

1

Duration Mode

Enter a Start Time (e.g., 9:00 AM) and an End Time (e.g., 5:00 PM). The tool calculates the elapsed hours and minutes.

2

Overnight Handling

If your End Time is earlier than your Start Time (e.g., Start 10 PM, End 2 AM), the calculator automatically assumes the next day.

3

Add/Subtract

Need to know when a 4-hour 30-minute movie finishes if you start at 8:15 PM? Use the "Add Time" mode to find the exact finish time.

Understanding Decimal Hours

❓
The Problem

"8 hours and 30 minutes" is NOT 8.30 hours. This is a common payroll mistake.

💡
The Math

Divide minutes by 60. 30 ÷ 60 = 0.5. So 8h 30m = 8.5 hours.

📄
Payroll Use

Timesheets often require decimal format. This tool converts it for you automatically.

Related Planning Tools

📅 Date Calculator → 💼 Work Hours Calc → 🎂 Age Calculator → 💵 Hourly Rate Calc →

Frequently Asked Questions

How many minutes are in a decimal hour?
A decimal hour is based on 100 units, while a clock hour is 60 minutes. To convert 0.1 hours to minutes: 0.1 × 60 = 6 minutes.
Does this calculate across different days?
Yes. In "Duration" mode, if you enter a start time of 11:00 PM and an end time of 1:00 AM, the calculator assumes the end time is the next day (2 hours duration).
Can I calculate timesheets with this?
Absolutely. Use the Duration mode to find the hours worked between your clock-in and clock-out times. The decimal hours result is perfect for payroll input.
What is 100 minutes in hours?
1 hour is 60 minutes. So 100 - 60 = 40. The result is 1 hour and 40 minutes (or 1.67 decimal hours).
Does this support seconds?
The "Add/Subtract" mode supports inputting specific seconds. The "Duration" mode focuses on Hours:Minutes for standard time clock usage.
How do I subtract 30 minutes from 2:00 PM?
Use "Add/Subtract" mode. Set Start Time to 14:00 (2:00 PM), select "Subtract", and enter 30 minutes. The result will be 1:30 PM.
Is military time (24h) supported?
Yes. The input fields use your device's native time picker, which usually supports both 12h and 24h formats depending on your system settings. The calculations work correctly regardless.
Why do airlines use 24-hour time?
To avoid confusion between AM and PM, which can lead to missed flights. 05:00 is always morning, 17:00 is always evening.
What time is 18:00?
18:00 minus 12 equals 6. So it is 6:00 PM.
Can I calculate a countdown?
For a live countdown, use a dedicated stopwatch tool. This calculator finds the fixed duration between two static timestamps.