Which USB-C cable do you need for 100W laptop charging?
USB Power Delivery, 5-amp cables, e-markers and the 60W and 240W logos, explained from the USB Implementers Forum's own documents.
Short answer
For 100W you need a USB-C to USB-C cable rated for 5 amps. A standard USB-C cable is rated for 3 amps, which at 20 volts is 60W. A cable can only be used at 5 amps if it carries an electronic marker chip, or e-marker, that reports that rating to the charger. On certified cables, a USB-IF logo with “240W” means a 5-amp cable; a logo with “60W” means charging will be limited to 60W.
Why 100W needs a different cable
Power is volts multiplied by amps. For 100W at 20 volts, the cable has to carry 5 amps: 20 V × 5 A = 100 W. The USB Implementers Forum (USB-IF), the industry group that runs USB certification and logos, describes the limit this way: “Prior to this update, USB PD was limited to 100W using a solution based on 20V using USB Type-C cables rated at 5A.”
“This update” is USB Power Delivery Revision 3.1, announced in 2021. It added fixed voltages of 28, 36 and 48 volts, which the USB-IF says allow up to 140W, 180W and 240W. A 100W charge sits inside the older 20-volt range, so for a 100W laptop the cable's current rating, 3 amps or 5 amps, is what decides whether you get the full power.
3 amps or 5 amps: what the e-marker does
The USB Type-C cable specification sets the baseline. It says that standard USB-C cable assemblies “are rated for 3 A”, and that cables designed for USB Power Delivery and “appropriately identified via electronic marking are allowed to support up to 5 A”.
That electronic marking is a small chip in the plug, the e-marker. When the charger asks, the chip answers with information about the cable, including how much current it can carry. Without that answer, the charger has to treat the cable as a standard 3-amp cable, and 3 amps at 20 volts is 60W.
Two details catch people out:
- An e-marker on its own doesn't mean 5 amps. The chip reports the cable's rating, and that rating can be 3 amps. The specification requires an e-marker in every full-featured USB-C cable, the kind with extra wires for USB 3 and faster data, whatever its current rating.
- A USB 2.0 or charge-only USB-C cable may have no e-marker at all. The specification says USB 2.0 Type-C cables “may be electronically marked”. One without an e-marker is a 3-amp cable.
What the logos on the box mean
The USB-IF certifies cables and licenses logos for them. Its cable logo guidelines give USB-C to USB-C cables a power rating of 60W or 240W; the combined logos add a data speed, such as 80Gbps alongside 240W. A cable may use these logos only after it has passed USB-IF compliance testing and appears on the USB-IF's list of certified products. The USB-IF's logo requirements tie the 240W rating to testing against USB Power Delivery's Extended Power Range.
| What you see | What it means | With a 100W charger |
|---|---|---|
| USB-IF certified logo with “240W” | A 5-amp cable, tested for USB Power Delivery's Extended Power Range | Carries the full 100W |
| USB-IF certified logo with “60W” | A 3-amp cable | Limited to 60W |
| “100W” or “5A” in the product name, no USB-IF logo | The seller's own rating, not a certified one | Should carry 100W if the claim is accurate; look for “5A” and “e-marker” on the maker's specification page |
| No power rating anywhere | Assume a standard 3-amp cable | Expect 60W at most |
A 240W cable works with a 100W charger. The charger and laptop still settle on 20 volts and up to 5 amps; the cable's extra voltage rating simply goes unused.
The cable is one of three parts
Charging runs at the lowest rating among the charger, the cable and the laptop. A 5-amp cable won't make a 65W charger deliver 100W, and a laptop that accepts at most 65W over USB-C won't draw 100W from a 100W charger. Check the laptop maker's specification page for its USB-C charging wattage, and the charger's label for its USB-C output in watts.
How to check a cable you own or are about to buy
- Look for the USB-IF logo with a wattage on the packaging. The logo guidelines also allow it to be printed or engraved on the cable's plug molding.
- Search the brand and model in the USB-IF product search. The USB-IF says the search is limited to products that have passed its compliance program.
- No logo? Open the cable maker's own specification page and look for a current rating of 5A, or the words “e-marker” or “e-marked”. A wattage in a product title on its own is the weakest evidence.
- Still can't tell? Plan on 60W from that cable.
Sources
- USB-IF, USB Charger (USB Power Delivery): the 100W limit at 20V with 5A cables; 28V, 36V and 48V for 140W, 180W and 240W. Read October 1, 2026.
- USB 3.0 Promoter Group, USB Type-C Cable and Connector Specification, Release 2.0 (August 2019), section 2.4 (3 A and 5 A cable ratings) and section 4.9 (electronically marked cables). The USB-IF says a later release, 2.1, defines the 240W cable requirements. Read October 1, 2026.
- USB-IF, USB Type-C Cable Logo Usage Guidelines (file dated September 2024): 60W and 240W power-rating logos, combined power and speed logos, certification requirement. Read October 1, 2026.
- USB-IF, Licensed Mark(s) Requirements: test procedures behind the 60W and 240W cable logos. Read October 1, 2026.
- USB-IF, Product Search: the certified product list. Read October 1, 2026.
Changes: first published October 1, 2026.