How can I make sure I'm buying the right laptop charger online?

You need to consider certain things before buying the adapter/charger for your laptop.
First check the voltage and amperage. It does not matter if the amperage on the charger is higher than the amperage on the laptop. Make sure you have the right polarity by looking for a symbol on your laptop and your charger that looks like these :

 if there both the same and the voltage and amperage is good than you can charge your laptop.

Choosing a Replacement Adapter:

Find your laptop’s model number.
You may find this number located on a sticker on the bottom or side of your laptop computer. If you can’t find it there, check your user manual or search your laptop’s built-in help program for the model number. You can also find it under your laptop’s system properties.

Find your wattage requirements.
In addition to your laptop model number, you will need to find out the voltage requirements for the laptop adapter. Laptop adapters have varying voltage (V) outputs, and using the wrong laptop adapter can damage your computer. Check your user’s manual for voltage requirements information for your laptop. The output voltage will usually be listed as DC voltage. You may also want to check for product or part numbers that are compatible with your laptop model.

Find a compatible laptop adapter.
Look for the compatibility lists in descriptions of laptop adapters you are looking at. Sometimes the compatible laptop models are listed in the product description or in a separate list. Laptop model numbers can often look similar, so make sure the model numbers match exactly. Laptop adapter and power cord product descriptions typically list the manufacturer, part number and a partial description as well. If you find an adapter with the correct output voltage, but the wrong port connector, you may be able to find port attachments that will adapt the connector to the power port on your laptop.

---

Ac Adapter : ASUS Ac Adapter Acer Ac Adapter Apple Ac Adapter Clevo Ac Adapter Compaq Ac Adapter Dell Ac Adapter Fujitsu Ac Adapter Gateway Ac Adapter Google Ac Adapter Hp Ac Adapter LG Ac Adapter Lenovo Ac Adapter Microsoft Ac Adapter Msi Ac Adapter Nec Ac Adapter Panasonic Ac Adapter Philips Ac Adapter ResMed Ac Adapter Resmen Ac Adapter Samsung Ac Adapter Sony Ac Adapter Toshiba Ac Adapter