Find out how long your computer has been on since the last restart
You can check how long your computer has been running without restarting by opening a single command or looking at your system settings. The time shown tells you how many days, hours, and minutes have passed since your last startup or restart — not since you first bought the machine. On Windows, the quickest method takes about 30 seconds. On Mac, you have two straightforward options that take even less time.
Knowing your uptime matters for a few real reasons. If your computer has been running for weeks without a restart, it may slow down or use more power. Some software updates require a restart to take effect, and security patches work better on a freshly booted system. If your machine crashes or freezes, checking the uptime can help you figure out whether the problem started after a specific event or has been building over time.
Key Takeaways
- On Windows, open the Command Prompt and type systeminfo to see "System Boot Time" — the exact date and time your computer last started.
- On Windows 10 and 11, you can also check Settings > System > About and scroll down to "System uptime" for a simpler display.
- On Mac, open System Settings > General > About and look for "System Uptime" to see days, hours, and minutes in plain language.
- If you see your computer has been on for more than two weeks, restarting it can improve speed and ensure security updates are fully installed.
- The uptime shown is time since your last restart, not time since you last used the computer — it keeps running even when you sleep it.
Check uptime on Windows using Command Prompt
The Command Prompt method works on all versions of Windows and gives you the exact date and time your computer last booted. Open the Command Prompt by pressing the Windows key, typing cmd, and pressing Enter. A black window will open with a blinking cursor.
Type systeminfo and press Enter. The system will display a list of information about your computer. Scroll down or search for the line that says "System Boot Time." This line shows the exact date and time your computer last started. If your computer started on January 15 at 9:47 AM and it is now January 22 at 2:15 PM, you can calculate that your computer has been on for about 7 days and 4.5 hours.
If you find the Command Prompt confusing, close it by typing exit and pressing Enter, then try the Settings method instead.
Check uptime on Windows 10 and 11 through Settings
Windows 10 and 11 include an uptime display in the Settings app that shows the time in a more readable format. Press the Windows key and type settings, then press Enter. The Settings window will open.
Click on System in the left sidebar, then scroll down and click About. Look for the line labeled "System uptime." Windows will display how many days, hours, and minutes your computer has been running since the last restart. This method is faster than Command Prompt and does not require you to do any math.
If you do not see "System uptime" in the About section, your version of Windows may be older. Use the Command Prompt method instead, or restart your computer and try again — sometimes the setting takes a moment to appear after a fresh boot.
Check uptime on Mac using System Settings
Mac computers display uptime directly in System Settings. Click the Apple menu in the top-left corner of your screen and select System Settings (or System Preferences on older Macs). The Settings window will open.
Click General in the sidebar on the left. Then click the About button. Look for the line that says "System Uptime." Mac will show you the number of days, hours, and minutes your computer has been on since the last restart in plain language — for example, "5 days, 3 hours, 22 minutes."
Check uptime on Mac using Terminal
If you prefer using the Terminal app, you can see your uptime in seconds. Open Terminal by pressing Command + Space, typing terminal, and pressing Enter. A text window will open.
Type uptime and press Enter. Terminal will display a line showing your current time, how long the system has been running, how many users are logged in, and the system load. The uptime appears after "up" — for example, "up 5 days, 3:22" means your computer has been running for 5 days, 3 hours, and 22 minutes. Close Terminal by typing exit and pressing Enter.
What to do if your computer has been on too long
If your uptime shows more than two weeks, consider restarting your computer. A restart clears temporary files from memory, closes programs that may have developed small errors, and installs any pending security updates that require a reboot to take effect.
Before you restart, save any open work and close programs you are using. Then click the Start menu (Windows) or Apple menu (Mac) and select Restart. Your computer will shut down and start back up, which usually takes two to five minutes. After the restart, your uptime will reset to zero days, zero hours, and zero minutes.
If your computer is part of a work network, check with your IT department before restarting — some systems have scheduled maintenance windows or updates that should happen at specific times.
Understanding what uptime does and does not tell you
Uptime measures only the time since your last restart. It does not measure how long you have actually been using the computer. If you restart your computer at 8 AM and then put it to sleep at 9 AM, the uptime will still count the sleeping time. When you wake the computer at 5 PM, the uptime will show 9 hours even though you only actively used it for 1 hour.
Uptime also does not account for time your computer spent in hibernation or powered off. If you shut down your computer completely and turn it back on the next day, the uptime counter starts over at zero. Only restarts — which shut down the system and immediately boot it back up — reset the uptime counter.
A high uptime number does not necessarily mean your computer is broken or in trouble. Many servers and work computers run for months without restarting. However, for personal computers used at home or in an office, restarting every two to four weeks helps keep the system running smoothly.
Frequently Asked Questions
Does sleep mode reset the uptime counter?
No. When you put your computer to sleep, the uptime counter keeps running. Only a full restart — which shuts down the system and boots it back up — resets the uptime to zero. Shutting down completely and turning the computer back on later also resets the counter.
Why does my uptime show a time from several days ago even though I turned my computer off last night?
You likely put your computer to sleep instead of shutting it down. Sleep mode keeps the system running in the background, so the uptime counter continues. To fully shut down, click the power button or use the shutdown option in your system menu, not the sleep option.
Can I check uptime on my work computer without administrator permission?
Yes. Both the Command Prompt method and the Settings method work without special permissions. However, if your work computer is locked down by IT, some system information may be hidden. Try the Settings method first — it usually works on restricted computers.
Does restarting my computer delete my files?
No. A restart shuts down your operating system and starts it back up, but it does not delete files on your hard drive. Save any open work before you restart, because unsaved documents in open programs will be lost when the system shuts down.
What if the uptime keeps resetting every few hours?
Your computer may be restarting automatically due to a Windows update, a power issue, or a hardware problem. Check Windows Update to see if updates are scheduled to install. If restarts keep happening without your input, contact your IT support or a technician — this can indicate a failing hard drive or power supply.