Tool
USB-C charger calculator: what wattage and cable does your laptop need?
Two numbers decide it: the wattage your laptop's own charger puts out, and everything else you plug in at the same time. Enter them and this works out the charger size and the cable rating.
orW
Look for “Output” on the brick. 20V ⎓ 3.25A is 65W (volts × amps).
You need
100W charger
- 65W for the laptop + 20W for the rest = 85W at once. Ports share the total, so a charger sized for the laptop alone slows down when the phone joins.
- Check the single-port figure too: the port the laptop uses must deliver 65W on its own.
- Cable: 100W (5A, e-marked) USB-C cable. A thin phone cable silently caps the connection at 60W.
Chargers we have reviewed that fit
Cables that carry it
Power banks that can keep up
Questions this answers
Can I use a higher-wattage charger than my laptop came with?
Yes. USB-C chargers and laptops agree on power before any flows, so the laptop only draws what it asks for. A 100W charger on a 65W laptop runs it at 65W and leaves the rest for other ports.
What happens with a lower-wattage charger?
Most USB-C laptops still charge, just slowly, and under heavy load the battery can drain while plugged in. Some refuse chargers below a minimum (often around 30W) or warn that the charger is too weak.
Why does the cable matter?
A USB-C cable without an e-marker chip is limited to 3A, which is 60W at 20V. Above 60W you need a 5A (100W) cable, and above 100W a 240W cable rated for USB PD 3.1.
How do I find my laptop's wattage?
It is printed on the charger as an output such as 20V ⎓ 3.25A. Multiply volts by amps: 20 × 3.25 = 65W. The laptop's support page lists it too.
The product suggestions are reviews on this site filtered by the wattage in their Amazon listing title. We have not bench-tested them; each review says what it is based on. For the reasoning behind the numbers, see how many watts you need and why charging through a hub is slow.