Charger and cable wattage checker
Pick your device, your charger and your cable. See if they charge at full speed, slower, or not well, and what holds them back.
This checker needs JavaScript. The quick rules further down give the same answers by hand.
This is a guide, not a guarantee. It follows the USB specs and maker pages listed below, but chargers, cables and devices don't always behave exactly as specified. A cheap or worn cable can be slower than its label.
Quick rules
| Part | Rule |
|---|---|
| Normal USB-C cable | Up to 60W (20V at 3A). Most cables without a marking fall here. |
| 5A e-marked USB-C cable | Up to 100W (20V at 5A). |
| 240W USB-C cable | Up to 240W (48V at 5A), with an EPR charger and device. Needed above 100W. |
| USB-A to USB-C cable | No USB PD. Usually 5V only, about 7.5W to 12W, or about 18W with Quick Charge 3.0. |
| Charger without USB PD | At most 15W (5V at 3A) to a USB-C device. |
| Charger without PPS | Samsung Super Fast Charging won't work. Expect about 15W instead. |
| Bigger charger than needed | Safe. The device only takes what it asks for. |
How the checker works
1. The weakest part sets the speed. We take the lowest of three limits: what the device can take, what the charger port gives, and what the cable carries.
2. Both ends must speak the same method. USB PD fast charging needs USB PD in the charger and the device, and USB-C at both ends. Samsung's Super Fast Charging also needs PPS, a part of USB PD. Without a shared method, the device falls back to slow 5V charging.
3. Cables have a current limit. Normal USB-C cables carry 3A, so 60W at 20V. Only cables with an e-marker chip carry 5A, for 100W. Above 100W, USB PD 3.1 uses higher voltages (28V, 36V or 48V), which need a 240W cable.
4. The verdict. "Full speed" means the combo can give what the device can take. "Charges, but slower" means at least half. Below half, or a laptop on 15W or less, is "Will not charge well".
Questions
Is a bigger charger safe for my phone?
Yes. A USB PD charger only gives what the device asks for, so a 65W or 100W charger is safe for a phone that takes 25W.
Why does my laptop say it is charging slowly?
The charger, the cable or both give less than the laptop wants. A 65W laptop on a 30W charger charges slowly and may drain while in use. A normal 60W cable also limits a 100W charger.
How do I know what my USB-C cable can carry?
Certified cables show a 60W or 240W logo on the plug or the box. A cable with no marking should be treated as 60W. Only cables with an e-marker chip carry 5A, for 100W or more.
Does a USB-A to USB-C cable fast charge?
Not with USB PD, which needs USB-C at both ends. USB-A usually gives 5V, about 7.5W to 12W, or up to about 18W with Quick Charge 3.0.
What is PPS and do I need it?
PPS (Programmable Power Supply) is part of USB PD. Samsung's Super Fast Charging needs it. Without PPS, those phones charge at about 15W instead of 25W or 45W.
Does it cover wireless, MagSafe or Lightning?
No. It covers wired USB-C and USB-A charging only. Wireless and magnetic charging have their own limits and lose more power as heat.
Charging away from a wall? Try the power bank calculator or read the power bank buying guide. More tools are on the tools page.
Sources
All sources were checked on October 30, 2026.
- USB PD power levels (100W limit with 5A cables, 240W with 28V, 36V and 48V): USB-IF: USB Charger (USB Power Delivery) and USB-IF: USB Power Delivery specification
- Cable ratings and the 60W and 240W logos: USB-IF: Cables and connectors, USB-IF: cable power rating logos (PDF) and USB-IF: USB Type-C cable and connector specification
- 3A and 5A voltage steps, and PPS: Texas Instruments: USB Type-C and USB PD, Extended Power Range (PDF)
- USB-A charging (7.5W): USB-IF: Battery Charging v1.2 specification
- Samsung charging types, PPS and 5A cables: Samsung: which charger does my Galaxy accept? and Samsung: fast charging on Galaxy phones
- Quick Charge and USB PD: Qualcomm: Quick Charge 4+
- 140W laptops and 240W cables: Apple: fast charge your MacBook Air or MacBook Pro