Watts are the total power a cable can carry, amps are the amount of current that flows through it. Together with the voltage, they determine how fast your device charges. A cable rated for 100 watts and 5 amps can even power a laptop; a regular phone cable often tops out around 60 watts. Note: charging is never faster than the weakest link, whether that's the charger, the cable or the device.
Watts, volts and amps: how does it all fit together?
The three numbers are linked. Power in watts is voltage in volts multiplied by current in amps. So a charger with 20 volts and 5 amps delivers 100 watts. A cable has its own limit: it can safely carry a certain number of amps. If your device, charger and cable aren't matched, charging happens at the lowest common denominator.
| Term | Unit | What it means |
|---|---|---|
| Voltage | volts | the pressure with which current is delivered |
| Current | amps | how much current flows per second |
| Power | watts | volts times amps, the total charging power |
How many watts do you need?
Roughly speaking: a phone is happy with 20 to 30 watts, a tablet with 30 to 45 watts, and a light laptop needs 60 watts or more. A cable rated up to 100 watts covers all these cases at once, so you don't need a different cable for every device.
Which cable should you choose?
For a laptop and fast charging, go for a sturdy, high-power cable, such as the braided Ugreen USB-C cable. If you're mainly charging a phone or tablet, an original Apple USB-C cable will do just fine, and if you want a braided version that holds up better to daily use, there's the woven Apple USB-C cable.
How to spot a slow cable
- Your device charges noticeably slower than with another cable.
- The cable or plug gets warm during charging.
- Your phone doesn't show a fast-charging notification even though the charger supports it.
- A thin, unreinforced cable kinks easily and breaks on the inside.
Why does my device sometimes still charge slowly?
Even with a good cable, charging can disappoint, and that's almost never down to the cable alone. An old charger that only delivers 5 watts drags down the whole system, no matter how much the cable can handle. A phone that's almost full deliberately charges more slowly to protect the battery, and the same happens if the device gets too hot. A dirty or slightly damaged USB-C port also adds resistance. So if charging is slow, work through the whole chain: first the charger and its power, then the cable, then the port, and only then the device itself. That way you know for sure which link is holding things back before you replace anything.
Does a more expensive cable always charge faster?
No. Beyond what your device and charger can handle, extra power adds nothing; the ceiling is set by the weakest link.
Is 100 watts dangerous for a phone?
No, your phone never draws more than it can handle. A 100-watt cable simply delivers less when the device asks for less.
Does a USB-C cable work in both directions?
Yes, USB-C is reversible and works at both ends no matter which way you plug it in.
