When to use it
Use this converter to switch between milliseconds, seconds, minutes, hours, days, weeks, months, years, decades and centuries. It is handy for timesheets and billing in decimal hours, programming timeouts in milliseconds, project plans in weeks, and school questions about large spans of time.
How to use it
- Enter the amount in Value.
- Choose the unit you have, such as Hours (h).
- Choose the unit you want, such as Minutes (min).
- Read the result, or click Copy result.
- Use the swap button to reverse the conversion.
The All conversions table shows the same length of time in every unit at once.
Worked example
A timesheet says you worked 2.5 hours. Enter 2.5, choose hours and minutes, and the result is 150 minutes. The table also shows 9,000 seconds and 9,000,000 milliseconds.
For a programmer, a timeout of 90 seconds is 90,000 ms. Choose seconds and milliseconds to check.
For a big number, one billion seconds sounds short but is about 31.7 years. Enter 1000000000 with seconds and years selected to see it.
Turning a decimal back into hours and minutes
If the result is 3.4 hours, keep the 3 as hours and multiply the 0.4 by 60 to get 24 minutes, so 3 hours 24 minutes. The same trick works for days: 2.25 days is 2 days plus 0.25 × 24 = 6 hours.
Milliseconds in code
Many programming languages measure time in milliseconds. JavaScript timers, for example, take 1000 for one second and 60000 for one minute. Converting here avoids an extra zero slipping in.
Decimal hours quick reference
| Minutes | Decimal hours |
|---|---|
| 6 | 0.1 |
| 15 | 0.25 |
| 30 | 0.5 |
| 45 | 0.75 |
Tips
- Use decimal hours for pay. Multiply decimal hours by your hourly rate. 2.75 hours at $20 is $55.
- Use the table for planning. Seeing a project’s length in days and weeks side by side helps with deadlines.
- Use exact dates for contracts. For notice periods or due dates, count calendar days with the Date Difference Calculator.
Common mistakes
- Reading decimals as minutes. 1.2 hours is 1 hour 12 minutes, not 1 hour 20 minutes.
- Assuming every month is 30 days. The converter uses an average month, so short spans in months are approximate.
- Forgetting leap years. Over long periods, the extra quarter day each year adds up to about a week every 28 years.