The safest way to think about this is to start with the circuit, not the room. A room can have a lot of devices in it, but what matters is how much the specific breaker and wiring feeding that room can handle. In many homes, bedroom receptacles are on a 15-amp or 20-amp branch circuit. That does not mean you should plan to use the full breaker rating continuously. As a practical rule, if you expect regular loads like a computer, TV, chargers, and especially a space heater, the circuit can fill up faster than people realize.
Before adding an outlet, figure out what else is already on that circuit. Turn off the breaker and see what loses power, or use a circuit tracer if you have one. Then check the breaker size and wire gauge if you can safely access it. A 15-amp circuit usually uses 14-gauge wire, and a 20-amp circuit usually uses 12-gauge wire. The new outlet itself does not increase the load by being there; it just gives you another place to plug things in. The real issue is whether you are adding more demand than the circuit was designed to carry.
If the room already runs a space heater, that is the big warning sign. Space heaters commonly draw around 1,500 watts, which is roughly 12.5 amps on a 120-volt circuit by itself. That leaves very little room for anything else on a 15-amp circuit and not much on a 20-amp circuit either. If a heater is part of the normal use, I would strongly consider having a dedicated circuit installed instead of just tapping into the existing one. That is especially true if the room also has a computer setup, printer, gaming console, or other electronics that may run for hours.
If you are only adding an outlet for light loads, the job may be straightforward if there is an accessible existing outlet nearby and the circuit has room. Use proper electrical boxes, match the wire size to the circuit, and make sure all connections are secure and enclosed. Never use backstabbing on receptacles if you can avoid it; side screws or properly rated clamp terminals are better. Also, if you are extending from an existing box, check box fill so the box is not overcrowded with conductors and devices.
One thing people often miss is that the breaker protects the wire, not your devices. If the circuit trips often, that is not something to ignore or solve with a bigger breaker. The wiring has to match the breaker size, and the load has to stay within safe limits. If you are not comfortable identifying the circuit or calculating the load, it is worth having a licensed electrician look at it. A quick inspection can save you from nuisance trips, overheated wiring, or an outlet that seems fine until winter hits and the heater turns on.
