Most phones charge on 5 to 20 watts, depending on the model and charger

The wattage your phone needs is determined by its battery size and charging technology, not by what you plug it into. A standard iPhone charges at 5 watts with an older charger, but can accept up to 20 watts with a newer one. Android phones vary widely — some Samsung models accept 25 watts or more, while budget phones often stick to 5 or 10 watts. The phone itself decides how much power to draw; plugging a 5-watt phone into a 65-watt charger will not damage it or make it charge faster.

Your charger's wattage is printed on the brick itself or in the manual. If you have lost the manual, the wattage usually appears as "5V/1A" (5 watts), "5V/2A" (10 watts), or "9V/2A" (18 watts) — multiply the voltage by the amperage to get watts. If you cannot find it, a 5-watt charger is the safe baseline that works with nearly every phone made in the last decade.

Key Takeaways

  • Your phone will only draw the wattage it is designed for, so a higher-wattage charger will not overcharge or damage the battery.
  • Older iPhones charge at 5 watts, newer iPhones at up to 20 watts, and many Android phones at 18 to 25 watts or higher.
  • The wattage is printed on the charger brick as voltage and amperage (for example, 5V/2A means 10 watts).
  • Using a charger with lower wattage than your phone supports will charge it more slowly but will not harm the battery.

How to find your phone's charging wattage

Check your phone's original manual or the manufacturer's website for the rated charging wattage. Apple lists this in the technical specifications for each iPhone model. Samsung, Google, and other Android makers do the same on their support pages — search "[your phone model] charging watts" or "[your phone model] specifications".

If you cannot find the manual, look at the charger that came in the box. The wattage is usually printed in small text on the back or side of the brick. Write down the voltage (V) and amperage (A), then multiply them: a charger marked "5V/2A" is 10 watts, and one marked "9V/2.2A" is about 20 watts.

Why wattage matters for charging speed, not safety

Higher wattage means faster charging because more power flows to the battery each second. A phone that supports 20 watts will charge roughly twice as fast with a 20-watt charger as it would with a 5-watt charger. This is purely about convenience — a 5-watt charger will still charge the same phone, just more slowly, usually taking an extra hour or two.

The safety concern is reversed from what many people assume: using a charger with lower wattage than your phone supports is harmless. Using a charger with higher wattage is also harmless, because your phone's charging circuit limits how much power it accepts. A phone designed for 10 watts plugged into a 65-watt charger will draw only 10 watts. The extra capacity sits unused.

What happens if you use the wrong wattage charger

A charger with lower wattage than your phone supports will charge the phone more slowly but cause no damage. If your phone normally charges at 20 watts and you use a 5-watt charger, it will take longer — sometimes three to four hours instead of one — but the battery will not degrade faster or fail.

A charger with higher wattage than your phone supports will not harm the phone or battery. Your phone's internal charging circuit recognizes the charger and draws only the power it needs. This is why you can safely use a laptop charger (often 60+ watts) to charge a phone that normally uses 10 watts.

The real risk is using a charger from an unknown or very cheap manufacturer that does not properly regulate power output. These rare chargers can deliver unstable voltage, which may damage the phone's charging port or battery over time. Stick to chargers from the phone's manufacturer or from reputable third-party makers like Anker or Belkin.

Matching a replacement charger to your phone

If you need a new charger, match the wattage to what your phone supports or go slightly higher — going higher is safe and gives you flexibility if you upgrade phones later. A 20-watt charger works with phones that support 5, 10, or 20 watts. A 30-watt charger is a good middle ground for mixed households with older and newer phones.

Check the connector type as well. Older iPhones use Lightning, newer iPhones use USB-C, and Android phones use either USB-C or Micro-USB. Buying a charger with the wrong connector is the only way you will actually be unable to charge the phone. The wattage mismatch is never a problem.

Wireless charging and wattage

Wireless chargers are rated in watts the same way, but the wattage is usually lower — typically 5 to 15 watts. A phone that charges at 20 watts over a cable may charge at only 10 watts wirelessly, because the magnetic coupling between the charger and the phone is less efficient than a direct connection. Wireless charging is slower by design, not because of a safety issue.

If your phone supports wireless charging, the manual will state the maximum wireless charging wattage. Using a wireless charger with higher wattage than your phone supports is safe; the phone will draw only what it needs. Using one with lower wattage will straightforward charge the phone more slowly.

Frequently Asked Questions

Can I use a fast charger on an old phone?

Yes. A fast charger (20 watts or higher) will not damage an older phone. The phone will draw only the wattage it was designed for, and the rest of the charger's capacity will go unused. Charging speed will match what the old phone supports, not what the charger offers.

What wattage charger should I buy if I have multiple phones?

A 20 to 30-watt charger is a safe choice for most households. It will work with phones that support 5, 10, 15, or 20 watts. If you have a newer flagship phone that supports 30+ watts, match that wattage or go slightly higher. Every phone will charge safely at any wattage above what it supports.

Does charging at lower wattage make the battery last longer?

Slightly, but the difference is small. Slower charging generates less heat, and heat is the main thing that degrades phone batteries over time. Using a 5-watt charger instead of a 20-watt charger may extend battery life by a few months over several years, but the effect is minor compared to keeping the phone cool and avoiding deep discharges.

Is it bad to leave my phone plugged in overnight?

Modern phones have charging circuits that stop charging once the battery reaches 100 percent, so leaving it plugged in does not overcharge it. The battery will degrade slightly faster if left at 100 percent for long periods, but the effect is small. If you want to minimize battery wear, unplug it once it reaches full charge, but there is no safety risk in leaving it plugged in.