Go to the Windows System Tray on lower-left corner of your Windows desktop; usually there it a tiny Battery icon there. You can hover over it it or on some models you can right-click or left-click to open it for detail. Hovering will show the charge percentage; some laptops also give you the time to recharge or the time unplugged; it simply depends on the model laptop you have.
Also, these little applet programs are not always reliable on that calculated time anyway; the best way to test is to unplug your laptop AC charger from the laptop and leave the laptop running 1 or more programs; watching a DVD movie from disc or connecting to a streaming website such as Netflix are ideal for draining your battery and testing your battery charge time. Your laptop will eventually go dark and screen, lights, fans, hard drive will all shut off once the battery drains to zero.
If your battery fails to hold a charge for over 1 hour, it has failed and needs to be replaced. Also, if the battery is over 2 years old, it has almost certainly failed and should be replaced anyway. This is a much more accurate test than any utility in Windows will ever show you.