GoKawiilTo start, it's important to look at the type of laptop you have. The general range for modern laptops will lie somewhere between four and 12 hours from a single charge, but that's a pretty wide net. Premium-thin and Ultrabook laptops will last near the upper end of that tier (at eight to 12 hours, with some even reaching 15 under optimal conditions), whereas more standard laptops will last about six to 10 hours — or four to seven hours if it's a budget-friendly machine. Gaming laptops will drain significantly faster, and you should only expect about two to four hours from them.
A laptop's niche is only part of the equation, though, as the type of charger you're using can also subtly affect battery life. Aftermarket chargers in particular may not deliver the precise voltage you need and could end up stressing your battery. Though an aftermarket charger isn't a complete recipe for disaster, it's ill-advised if you want your battery to reach its full potential.
To reach that full potential for each of these bounds, you'll need to optimize things. There are some key settings to change for extended laptop battery life, such as turning down display brightness, closing background apps and tabs, and lowering your display's refresh rate. You could also switch to a power-saving mode in your laptop's power management settings, though you may need to switch out of this mode to carry out a demanding task.