On this page
01Match the charger to your phone's ceiling
For most iPhones, the 20W vs 30W charger question has a simple answer: by cable, 20W gets you to about 50% in 30 minutes, and 30W is only meaningfully faster on the iPhone 17 and 18 Pro generations. Where 30W earns its keep is behind a magnetic wireless charger.
| Phone | 20W | 30W | 45W or more |
|---|---|---|---|
| iPhone 12 to 16 | Full wired speed | Same by cable; needed for 25W MagSafe on 16 | No gain |
| iPhone Air | Full wired speed | Needed for 20W MagSafe | No gain |
| iPhone 17, 17 Pro | Fast, slower first half | Faster | 40W+ reaches Apple's 50% in about 20 min |
| iPhone 18 Pro, Pro Max | Works, slower start | Faster | 60W-capable gets 50% in about 15 min |
| Galaxy S26, S25 | Just under max | Full 25W (with PPS) | No gain |
| Galaxy S26+, S25 Ultra | Slow for these | 25W mode | 45W mode (PPS + 5A cable) |
| Galaxy S26 Ultra | Slow for this | 25W mode | 45W at 45W; 60W at 60W+ |
| Pixel 10 Pro | Below max | Full speed (with PPS) | No real gain |
Not sure which phone you have? Here's how to tell which iPhone you have in about ten seconds. Model-specific advice lives in our guides for the iPhone 18 Pro and Galaxy S26.
02Why doubling the watts doesn't halve the time
Phones only draw their peak power for the first chunk of the charge, roughly up to the halfway mark. After that the phone cuts the current to protect the battery, and by 80% it's trickling. A bigger charger shortens that first stretch and does nothing for the rest.
So the real-world gain from 20W to 30W on an iPhone 16 is close to zero by cable, and on an iPhone 17 Pro it's a few minutes off the first half. From 0 to 100%, the gap shrinks again because every charger spends the last 20% waiting on the phone. Try it below with your phone's battery size.
Before you buy a bigger brick, check the cable. A worn USB-C cable or a USB-A to USB-C cable can cap you well below 20W. Any good USB-C to USB-C cable carries 60W; Samsung's 45W mode needs a 5A cable rated 100W or more.
03The real reason to buy 30W: magnetic charging
Wireless chargers need extra headroom because some power is lost between the coils. Apple says its MagSafe Charger needs a 30W or higher adapter to deliver 25W on supported iPhone 16 and 17 models. On a 20W adapter, the same charger runs at a lower speed. Third-party Qi2 25W chargers usually ask for similar power.
If you only charge by cable, 20W is fine. If a magnetic stand or puck is part of your routine, 30W is the minimum we'd buy. Our blog post on how fast MagSafe charging is has the speeds by model.
04When 45W and up actually pays off
- Galaxy S Plus and Ultra models. They support Super Fast Charging 2.0 at 45W, and the S26 Ultra goes to 60W. You need PPS and a 5A cable to see it. Details in 25W vs 45W Samsung charger.
- iPads and small laptops. A tablet or MacBook Air can run on 30W, but charges faster with more. One 45W to 65W brick covers phone and laptop.
- Two devices at once. A multi-port charger splits its total. A 45W two-port brick might give the phone 20W and earbuds the rest, while a 20W single-port brick can't share at all.
- Future phones. Wired speeds keep creeping up on flagships. A 45W+ GaN charger is cheap insurance.
Is a bigger charger safe on a phone that wants less? Yes. The phone asks for the power it can handle, and a certified USB-C PD charger only supplies that. We cover the details in can I use a higher watt charger.
05Three sizes, three kinds of buyer
20W
- Smallest and cheapest
- Full wired speed on iPhone 12 to 16 and Air
- Too weak for 25W magnetic chargers
30W to 40W
- Runs magnetic chargers at full speed
- A little faster on iPhone 17 and 18 Pro
- Covers 25W Galaxy and Pixel with PPS
45W to 65W GaN
- Samsung 45W mode with PPS
- Charges a laptop too
- Overkill for a single iPhone
Check each listing for PD, and for PPS if you charge a Galaxy or Pixel.
Already have a drawer of old bricks? Read the output line on each. Anything that says 5V ⎓ 1A is a 5W cube: keep it for a bedside lamp or earbuds, not your phone. A USB-A brick with 2.4A is about 12W, which charges overnight but won't fast-charge a current iPhone or Galaxy. If a charger has a USB-C port and lists 9V on its output, it's almost certainly a PD charger and worth testing before you buy a new one. Our watts vs amps guide shows how to read those labels.
Questions people ask
Is a 30W charger better than 20W for iPhone?
By cable, only slightly, and mostly on iPhone 17 and 18 Pro models. The bigger benefit is wireless: Apple's MagSafe Charger needs 30W or more to reach 25W. If you only use a cable, 20W is enough for most iPhones.
Can I use a 45W charger on an iPhone?
Yes. iPhones negotiate the power they want through USB Power Delivery, so a 45W charger is completely safe. It'll charge newer Pro models a bit faster and leave headroom for a second device.
Is 20W fast charging for iPhone?
Yes. Apple's figure for a 20W adapter is about 50% in 30 minutes on supported iPhones. It's the minimum for fast charging, not the maximum. Newer iPhones can go faster with 40W or more.
Does a higher watt charger damage the battery?
No. The phone controls the charge rate. What wears batteries is heat and sitting at 100% for long periods, not the size of the brick. A charger that runs cool is gentler than a cheap one that gets hot.
What wattage charger do I need for an iPhone and iPad?
A 35W to 45W dual-port charger handles both at decent speed. If you charge them together often, go higher, since multi-port chargers split their power across ports.