Introduction
This Seconds Calculator helps you work with time in seconds. Type in a number, pick a unit, and get the answer right away. You can turn seconds into minutes, hours, days, weeks, months, or years — and go the other way too.
The tool has six tabs, each with a different job:
- Convert Seconds — change one time value into every other unit.
- Build Duration — add up years, days, hours, minutes, and seconds to get one total.
- Add / Subtract — put two time values together or find the gap between them, much like the Add Time Calculator and Subtract Time Calculator.
- Elapsed Time — count the seconds between a start date and time and an end date and time, similar to the Time Duration Calculator.
- HH:MM:SS Tool — switch between clock format and plain seconds.
- Batch Converter — convert a whole list of values at once and see the total.
Every answer comes with a step-by-step solution, so you can see the math and not just the number. Charts and tables show how the units compare. Use it for homework, workouts, cooking, video editing, work hours, or anything else that needs exact time math.
How to use our Seconds Calculator
Type in a time value, pick its unit, and this seconds calculator shows the answer in seconds, minutes, hours, days, weeks, months and years, plus a clock (HH:MM:SS) format and step-by-step math. Pick the tab that matches your job, then fill in the fields below.
Convert Seconds tab
Value to convert: Type the number you want to change, like 90061. Decimals such as 1.5 are fine.
Unit of the value entered: Pick what your number means right now — milliseconds, seconds, minutes, hours, days, weeks, months or years. For other kinds of unit swaps, the Unit Converter Calculator and Time Converter Calculator cover more ground.
Show the headline result in: Pick the unit for the big answer at the top. All other units still show below it.
Build Duration tab
Years, Months, Weeks, Days, Hours, Minutes, Seconds: Fill in any boxes you need and leave the rest at 0. The tool adds them all up into total seconds. If you only care about one unit, try the Minutes Calculator, Hours Calculator, Days Calculator or Weeks Calculator.
Show total in: Pick the unit for the total, such as seconds, hours or days.
Add / Subtract tab
First value (A): Type your first time, like 01:30:00 or 5400.
Format of A: Tell the tool how you typed value A — HH:MM:SS, milliseconds, seconds, minutes, hours or days.
Operation: Choose Add (A + B) or Subtract (A − B). To stack clock times in bigger chunks, see the Add Hours and Minutes Calculator, Add Hours Calculator or Add Minutes Calculator.
Second value (B): Type your second time value.
Format of B: Pick the unit or clock format you used for value B.
Elapsed Time tab
Use calendar dates: Turn this on when your start and end are on different days. Turn it off to work inside one day. For date-only spans, the Date Duration Calculator and Days Since Calculator are handy.
Start date: Pick the day your time began.
Start time: Enter the clock time you started, in HH:MM:SS.
End date: Pick the day your time ended.
End time: Enter the clock time you stopped, in HH:MM:SS. If you are logging shifts instead, the Time Card Calculator and Shift Calculator add up whole days of work.
HH:MM:SS Tool tab
Clock value (HH:MM:SS): Type a clock time like 01:30:45 to get total seconds. Hours over 24 are allowed. For payroll-style decimals, use the Time to Decimal Calculator or Minutes to Decimal Calculator.
Time value: Type a number, like 90, to turn it into clock format. Going from a decimal back to a clock reading is what the Decimal to Time Calculator does.
Unit: Pick the unit of that number — milliseconds, seconds, minutes, hours or days.
Batch Converter tab
Value (each row): Type one time value per row to convert many at once.
Unit for value (each row): Pick the unit for that row. Use Add Row for more values, then Convert All Rows to see the table and the combined total. To average a list of times instead of summing it, try the Average Time Calculator.
Seconds: The Base Unit of Time
A second is the standard unit of time. Every other time unit — minutes, hours, days, weeks, months, and years — is just a set number of seconds stacked together. That makes seconds the easiest way to compare two lengths of time, add them, or subtract them. Turn both values into seconds first, do the math, then turn the answer back into whatever unit you want.
How Many Seconds Are in Each Unit
| Unit | Seconds |
|---|---|
| 1 millisecond | 0.001 |
| 1 minute | 60 |
| 1 hour | 3,600 |
| 1 day | 86,400 |
| 1 week | 604,800 |
| 1 month (average) | 2,629,800 |
| 1 year (average) | 31,557,600 |
Why Months and Years Are Averages
Months are not all the same length. They run from 28 to 31 days. Years are not equal either, because a leap year adds one extra day every four years. So time math uses averages: a month is 30.4375 days and a year is 365.25 days. Those averages are great for rough planning. If you need an exact answer between two real calendar dates, count the actual days instead with the Date Calculator, the Month Calculator or the Weeks to Months Calculator.
Converting Time by Hand
To go from a bigger unit down to seconds, multiply. Two hours becomes 2 × 3,600 = 7,200 seconds. To go from seconds up to a bigger unit, divide. 7,200 seconds becomes 7,200 ÷ 3,600 = 2 hours. If a division leaves an awkward remainder, the Division Calculator and Modulo Calculator show the leftover clearly.
Reading HH:MM:SS Clock Format
Clock format shows hours, minutes, and seconds split by colons. To read it as one number, multiply the hours by 3,600, the minutes by 60, then add the seconds. So 01:30:45 is 3,600 + 1,800 + 45 = 5,445 seconds. For 24-hour clock readings, the Military Time Calculator handles the conversion.
Going the other way, you peel units off one at a time. Take 90,061 seconds. Divide by 86,400 to get 1 whole day, leaving 3,661 seconds. Divide that by 3,600 to get 1 hour, leaving 61 seconds. Divide by 60 to get 1 minute, leaving 1 second. The answer is 1 day, 1 hour, 1 minute, and 1 second.
Elapsed Time Between Two Moments
Elapsed time is how long something lasted. Change the start time and the end time into seconds past midnight, then subtract the start from the end. If the two moments fall on different dates, add 86,400 seconds for each full day in between. If the end time looks earlier than the start time on the same day, the clock crossed midnight, so add one day. When the two moments sit in different regions, check the Time Zone Calculator or the Time Difference Calculator first.
Where Seconds Get Used
Seconds show up in work timesheets, race and lap times, video and audio lengths, cooking timers, billing by the hour, and computer code. Runners lean on the Pace Calculator and Running Pace Calculator for split times, while file transfers are measured with the Download Time Calculator. Programs almost always store time as seconds or milliseconds, then format it for people to read.
Quick Facts Worth Remembering
- 1,000 milliseconds make 1 second.
- A million seconds is about 11.6 days.
- A billion seconds is close to 31.7 years — try it in the Age Calculator to see how that compares to a lifetime.
- An 8-hour work day is 28,800 seconds.
- Light travels about 299,792 kilometers in one second.