Time Calculator

What Is a Time Calculator?

A time calculator adds and subtracts time values — days, hours, minutes and seconds — which do not behave like ordinary decimal numbers because 60 seconds make a minute, 60 minutes make an hour and 24 hours make a day. Use it to total timesheet entries, add up the length of several videos, work out when a recipe will be ready, or find the date and time that falls a certain span after a given moment.

Three Ways to Use It

• Add or subtract two time values: for example, 2 h 45 m + 1 h 30 m = 4 h 15 m.
• Add or subtract from a date and time: start at a specific moment and move forward or backward by a number of days, hours, minutes and seconds to find the new date and time.
• Expressions: chain several amounts with + and −, such as 1d 2h 3m 4s + 4h 5s − 2030s, where d, h, m and s stand for days, hours, minutes and seconds.

Worked Example

Adding 2h 30m to 1h 15m gives 3h 45m total.

Time Units Cheat Sheet

• 1 minute = 60 seconds
• 1 hour = 60 minutes = 3,600 seconds
• 1 day = 24 hours = 1,440 minutes = 86,400 seconds
• 1 week = 7 days = 168 hours

Why Time Math Trips People Up

Because time uses a base-60 system for minutes and seconds, you cannot just add decimals. 1 h 45 m + 1 h 30 m is not 2.75 hours; it is 3 h 15 m, since 75 minutes carries over into another hour. The same carry-over happens between hours and days, and a calculator spares you the mental gymnastics. To work with decimal hours — handy for pay — divide minutes by 60: 45 minutes is 0.75 of an hour.

Common Uses

• Totaling hours worked across a week for payroll.
• Planning travel itineraries and layovers.
• Calculating cooking times, training durations and study blocks.

When you have a start and an end and want to know the length between them, use the Time Duration Calculator; for whole-day spans use the Date Calculator, and for converting hourly pay to annual income use the Salary Calculator.