Time Calculator
Last updated: March 2026
Quickly calculate time durations, add or subtract hours and minutes, or find the exact difference between two dates.
1️⃣ Add / Subtract Two Time Values
2️⃣ Add / Subtract Time From a Date
3️⃣ Time Expression Evaluator
About This Time Calculator
Calculating time can be confusing because it uses a base 60 system for minutes and seconds, not the standard base 10 decimal system we use for regular math. Standard calculators fail here. If you add 1.50 and 1.50 on a regular calculator, you get 3.00. But 1 hour 50 minutes plus 1 hour 50 minutes is actually 3 hours and 40 minutes.
Why this tool exists
We built this tool to handle the carries and borrows of time math automatically. It saves you from doing mental gymnastics when you need to add up work hours, figure out how much time is left on a project, or find the exact duration between two specific dates.
When should you use this tool?
- Payroll and Timesheets: Add up daily hours and minutes to get total weekly work hours.
- Flight Logs: Sum up flight durations for aviation compliance.
- Project Planning: Subtract elapsed time from a total time budget to see how many hours remain.
- Production Schedules: Calculate when a batch process will finish by adding a duration to a start time.
How the tool works
This calculator has three main sections. The first section lets you add or subtract two basic time values, like adding 2 hours to 45 minutes. The second section takes a specific calendar date and time, then adds or subtracts a duration to give you a future or past date. The third section is an expression evaluator where you can type out a string of math, like "2h 30m + 45m", and it will solve it all at once.
Limitations and Accuracy
This tool assumes standard 24 hour days and 60 minute hours. When calculating dates, it uses your device's local calendar and time zone settings. If your calculation crosses into different time zones or involves historical calendar changes, you will need to adjust the results manually. It does account for leap years automatically based on your local system calendar.
Frequently Asked Questions
Does this calculator handle leap years?
Yes. The date calculation mode uses your browser's built in calendar, which automatically accounts for leap years. Adding one year to February 29th, 2024, will correctly land on February 28th, 2025.
Can I calculate time for negative durations?
Yes. If you subtract a larger time value from a smaller one, the result will show a negative sign. This is very helpful for finding out how far behind schedule you are.
How do I convert decimal hours to minutes?
You multiply the decimal part by 60. For example, if you have 0.75 hours, multiply 0.75 by 60 to get 45 minutes.
Why do 100 minutes equal 1 hour 40 minutes?
There are 60 minutes in one hour. If you take 60 minutes out of 100 to make one full hour, you are left with 40 minutes.