If you are waiting for your laptop's battery to charge fully before heading out for the day, both OS X and Windows 10 will show you the time remaining.
Your battery will charge faster, of course, if you leave the lid closed and the screen off. If you are attempting to eek out the last few minutes of charging before running out the door, however, OS X and Windows 10 offer a quick glance at the time remaining before you reach 100 percent battery power. Both platforms also show the time remaining in System Preferences and Settings, respectively. Here's where to find that info.
On a MacBook, you can click on the battery icon in the menu bar to see how much time remains before your battery is full. And because you click instead of just hover over the icon, the window remains until you click your touchpad again or hit a key, which lets you keep an eye on the minutes that remain.
Alternatively, you can go to System Preferences > Energy Saver. On the Battery tab, the current battery charge percentage and the Estimated time until full is displayed.
On a Windows 10 laptop, when you mouse over the battery icon in the system tray, you can see how many minutes remain to a full charge. The time remaining stays on screen for only a few seconds, so if you want to keep an eye on the time remaining without continually tapping on the battery icon, head to Settings > Battery saver where you can watch the countdown to a full charge.
On battery power
The opposite holds true for the above advice when you are on battery power. Clicking the battery icon in the OS X menu bar or in the Windows 10 system tray shows you how much time remains before your laptop's battery runs out. You can also see the battery life remaining in System Preferences in OS X and Settings in Windows 10.