What does charger wattage actually mean?
Watts measure how much power a charger can supply, not how much your device will take. Here's how to read the number on the box.
The wattage on a charger is the most power it can supply. Your device decides how much it actually draws. That is why a 100W charger is safe for a phone: the phone simply asks for less.
Watts, volts and amps
Power (watts) is voltage multiplied by current: W = V × A. USB-C chargers raise the voltage to deliver more power without needing a huge current. A charger that offers 20V at 3.25A can supply 65W; the same charger might give a phone 9V at 2.22A, or 20W.
| Output level | Power |
|---|---|
| 5V × 3A | 15W |
| 9V × 3A | 27W |
| 15V × 3A | 45W |
| 20V × 3.25A | 65W |
| 20V × 5A | 100W |
Before power flows, the charger and device agree on one of these levels. You’ll find the list printed on the charger or in its manual, and we show it on each product page as “output levels.”
The number on the box isn’t always per port
On a multi-port charger, the headline wattage is usually the total, shared between ports. A “100W” three-port charger might give 100W to one laptop on its own, but only 80W once a phone and earbuds join. What one port can deliver alone, and what it gets while sharing, are separate questions. We list both. See why multi-port chargers split power.
How many watts do you need?
Check the charger that came with your device, or its spec sheet. As a rough guide:
- Phones: many charge at around 20–30W; some Android phones support 45W or more.
- Tablets: often 20–45W.
- Laptops: light models around 30W, most 13–15” laptops 45–65W, larger or high-performance laptops 90–140W.
- Watches and earbuds: a few watts.
A charger below your device’s rating will usually still charge it, just more slowly. Some laptops may only charge when switched off or idle, or show a “slow charger” warning.
Wattson’s take: More watts than you need won’t hurt, but it won’t make your phone charge any faster either. Buy for the most demanding device you’ll plug in.