Model unit
The laptop model is usually located on the underside of the device. Read it and enter it into the shop's search engine.
e.g. Asus K53SV / HP Pavilion G6 / MacBook Pro 13 A1278

Value of INPUT / OUTPUT
On the power supply nameplate, the voltage and current values are marked OUTPUT, and on the bottom of the laptop, the same parameters as INPUT are marked. Read some of them and enter them into the shop's search engine by adding the brand of the device. Make sure that the plug of the power supply found is correct.
e.g. Asus 19V 4.74A / Dell 19.5V 4.62A / Lenovo 20V 3.25A.

With such small differences it is acceptable. However, we must remember to use power supplies with higher power, not less, because at lower power the laptop may not work.

It will be suitable for our laptop if the plug diameter meets the outer diameter specification, e.g. 5.5 mm, and the output parameters are compatible. What are output parameters? It is the value of voltage[V] and current[A] that is given by the power supply for a laptop, e.g. 19V 4.74A.