ElectronicsInfoline

Will It Work? · Checker

Will this charger and cable fast-charge my device?

By Bulan Sarkar, founder of ElectronicsInfoline (since 2000)

A charger, a cable and a phone or laptop each set their own limit, and you get the lowest of the three. Type what the charger's label says, pick the cable, and enter the figure the device maker gives. The checker works it out from the USB Power Delivery and USB-C cable rules and shows its working.

You get the highest charger profile that both the cable and the device accept, capped at the device's maximum. A 65 W charger whose label reads 5V⎓3A 9V⎓3A 15V⎓3A 20V⎓3.25A gives a 65 W laptop 60 W on a 60 W cable (20 V × 3 A) and 65 W on a 5 A cable (20 V × 3.25 A). The cable decides it.

1. The charger

Copy them as printed, e.g. 5V⎓3A 9V⎓3A 20V⎓3.25A and a PPS range like 3.3-21V⎓3A. Read: 5 V × 3 A, 9 V × 3 A, 15 V × 3 A, 20 V × 3.25 A.

W

For a multi-port charger, the figure for the port you use.

2. The cable

No rating printed? Treat it as 60 W (3 A): only cables rated above 3 A must carry the e-marker chip.

3. The device (from its maker)

W
V

Laptops often list 20 V.

With limits60 W (20 V × 3 A)

Falls back to 60 W of the device's 65 W: the cable carries at most 3 A.

Show the working
  1. Cable: up to 3 A at up to 20 V (USB-C cable rated 60 W (3 A)).
  2. 5 V × 3 A = 15 W
  3. 9 V × 3 A = 27 W
  4. 15 V × 3 A = 45 W
  5. 20 V × 3 A (cable limit; charger offers 3.25 A) = 60 W
  6. Charger total: 65 W.
  7. Device maximum (maker): 65 W.
  8. Best agreed: 20 V × 3 A → 60 W.
Charging power is the lowest of three limitsCharger 65 W, cable 60 W, device 65 W. The result is 60 W.Charger offers65 WCable carries60 WDevice accepts65 WYou get60 W
Your three ceilings. The lowest one caps the charge; the working above gives the exact profile.

The rule the checker follows

With USB Power Delivery (PD) the charger lists its profiles, the device picks one, and the charger switches to it. Until they agree, the port stays at 5 V.

How a USB PD charger and device agree on powerThe charger lists its profiles (5 V 3 A, 9 V 3 A, 15 V 3 A, 20 V 3.25 A); the device asks for one; the charger agrees and switches to it. Until then the port stays at 5 V.ChargerDevice1. Here is what I offer5 V × 3 A = 15 W9 V × 3 A = 27 W15 V × 3 A = 45 W20 V × 3.25 A = 65 W2. I want this one3. Agreed: switching now
Figure 1. USB Power Delivery in three messages: the charger lists what it offers, the device asks for one profile, the charger agrees and changes voltage. The profile list here is an example label.
  1. Each fixed profile gives volts × the lower of its amps and the cable's amps.
  2. Profiles above 20 V (28, 36, 48 V) arrived with PD 3.1 (USB-IF) and need a 240 W cable and a device that asks for them.
  3. A PPS device on a PPS charger can use the PPS range instead, set in 20 mV steps (USB-IF).
  4. The result never passes the device's maximum or the charger's stated total.
  5. With no PD on one side, USB-C falls back to 5 V at 1.5 A or 3.0 A (USB-IF), so 15 W at most.
USB PD fixed voltagesFixed voltages 5, 9, 15, 20 V, then 28, 36, 48 V added in PD 3.1 for 140, 180, 240 W.5 V9 V15 V20 V28 V140 W36 V180 W48 V240 Wup to 100 W■ before PD 3.1■ added in PD 3.1 (needs a 240 W cable)
Figure 2. USB-IF: PD 3.1 added 28, 36, 48 V to the earlier 5, 9, 15, 20 V, for up to 140, 180, 240 W. Before that, PD stopped at 100 W (20 V on a 5 A cable).

Worked example: a 65 W charger and a laptop

Example label: 5V⎓3A 9V⎓3A 15V⎓3A 20V⎓3.25A, total 65 W. The laptop maker lists 65 W at 20 V. On a 60 W cable the 20 V profile is cut to 3 A: 20 × 3 = 60 W. On a cable rated 5 A it gets the full 3.25 A: 20 × 3.25 = 65 W.

Charging power is the lowest of three limitsCharger 65 W, cable 60 W, device 65 W. The result is 60 W.Charger offers65 WCable carries60 WDevice accepts65 WYou get60 W
Figure 3. The 60 W cable is the lowest limit, so the laptop gets 60 W from a 65 W charger.

What the cable ratings mean

Standard USB-C cables are rated 3 A; e-marked cables may carry up to 5 A, and every cable rated above 3 A must be e-marked (USB-IF). Before PD 3.1, PD stopped at 100 W: 20 V on a 5 A cable (USB-IF). The 240 W cable is tested at 48 V, 5 A (USB-IF).

USB-C cable ratings: 60 W and 240 WA 60 W cable carries 20 V at 3 A. A 240 W cable carries 48 V at 5 A and has an e-marker chip in the plug, which every cable rated above 3 A must have.60 W cable20 V × 3 Ae-marker chip240 W cable48 V × 5 A, chip in the plugA 3 A cable may also have a chip; above 3 A it must.
Figure 4. USB-IF figures: a 60 W cable is tested at 20 V, 3 A; a 240 W cable at 48 V, 5 A. Any cable rated above 3 A carries an e-marker chip that tells the charger what it can take.

More on this in USB-C cable ratings, and on fixed against programmable profiles in USB PD and PPS.

Tips and tricks

  • Read the output lines, not the big number on the front. A 65 W label tells you the total; the lines tell you which voltages you get.
  • For a laptop, look for the voltage it needs (often 20 V) on the charger’s label. A charger with no 20 V line may not charge it at all.
  • On a multi-port charger, the total is shared between the ports. Look in the maker’s manual for what one port gives when two devices are plugged in.
  • If a cable has no rating printed, assume 60 W (3 A). Only cables above 3 A must carry the e-marker chip.
  • A phone that says it needs PPS for its top speed still charges on plain PD, just slower. Check the maker’s figure before buying a new charger.

What we would do

Start with the device maker's figure: the maximum charging power, and whether it needs PPS or a particular voltage. Pick a charger whose label shows that voltage at enough amps, and a cable rated for the current: 60 W (3 A) covers anything up to 60 W, a 5 A cable covers up to 100 W, and only devices above 100 W need a 240 W cable.

If the checker says a cable is the limit, change the cable first. It is the cheapest of the three to fix.

Questions people ask

Why does my 65 W charger not charge my laptop at 65 W? Check the cable first. A USB-C cable rated 60 W carries 3 A, so at 20 V it stops at 60 W, even on a 65 W charger. Only a cable rated above 3 A (with an e-marker chip) carries the full 3.25 A. The device’s own maximum and the charger’s profiles are the other two limits.

Can I use a higher-watt charger than my phone needs? With USB Power Delivery the phone asks for the profile it wants and the charger supplies only that, so a bigger PD charger does not push more power into a phone than the phone requests.

What is the difference between a 60 W and a 240 W USB-C cable? The USB-IF tests a 60 W cable at 20 V and 3 A, and a 240 W cable at 48 V and 5 A. Every cable rated above 3 A carries an e-marker chip that tells the charger what it can take. You need the 240 W cable only for chargers and devices above 100 W.

Do I need a PPS charger? Only if the phone maker says its top charging speed needs PPS. A PPS phone still charges on an ordinary PD charger, through the fixed profiles, but slower. How much slower is the maker’s figure to give; the checker says so when it is not stated.

What happens with a charger that has no USB PD? The phone falls back to 5 V. Over USB-C, a charger can advertise 1.5 A or 3.0 A at 5 V without PD, so the most is 15 W.

Sources

Each figure on this page is quoted from the source below or worked out from them. Sources checked , each quote read again against the source in a second pass.

  1. USB-IF, USB Charger (USB Power Delivery) | USB-IF: Announced in 2021, the USB PD Revision 3.1 specification is a major update to enable delivering up to 240W of power over full featured USB Type-C® cable and connector. Prior to this update, USB PD was limited to 100W using a solution based on 20V using USB Type-C cables rated at 5A. usb.org/usb-charger-pd
  2. USB-IF, USB Promoter Group Announces USB Power Delivery Specification Revision 3.1 (Developer Update, May 26, 2021): A choice of three new fixed voltages: 28V (above 100W), 36V (above 140W) and 48V (above 180W) joining previously defined 5V, 9V, 15V and 20V fixed voltages. usb.org/sites/default/files/2021-05/USB%20PG%20USB%20PD%203.…
  3. USB-IF, USB Charger (USB Power Delivery) | USB-IF: New 28V, 36V, and 48V fixed voltages enable up to 140W, 180W and 240W power levels, respectively. usb.org/usb-charger-pd
  4. USB-IF, USB Power Delivery (USB Developer Days 2019, Taipei, slide deck): What is Programmable Power Supply (PPS) ... The Source output voltage adjustable in 20 mV steps ... The Source output current limit adjustable in 50 mA steps usb.org/sites/default/files/D2T2-1%20-%20USB%20Power%20Deliv…
  5. USB-IF, USB-IF Introduces Fast Charging to Expand its Certified USB Charger Initiative (press release, January 8, 2018): Certified USB Fast Chargers support the Programmable Power Supply (PPS) feature of the USB Power Delivery 3.0 specification. usb.org/sites/default/files/2018-08/certified_usb_fast_charg…
  6. USB-IF, USB Type-C Cable and Connector Specification, Release 2.0 (August 2019): The USB Type-C receptacle is specified for current capability of 5 A whereas standard USB Type-C cable assemblies are rated for 3 A. [...] Also, USB Type-C cable assemblies designed for USB PD and appropriately identified via electronic marking are allowed to support up to 5 A. usb.org/sites/default/files/USB%20Type-C%20Spec%20R2.0%20-%2…
  7. USB-IF, USB Type-C Cable and Connector Specification, Release 2.0 (August 2019): All cables that are either full-featured and/or are rated at more than 3 A current are Electronically Marked Cables. usb.org/sites/default/files/USB%20Type-C%20Spec%20R2.0%20-%2…
  8. USB-IF, USB Active Cable Thermal Compliance Test Specification, Revision 0.92 (draft): Power delivery is set to maximum specification: 60W (20V, 3A) for SPR cable, or 240W (48V, 5A) for EPR cable. usb.org/sites/default/files/USB%20Active%20Cable%20Thermal%2…
  9. USB-IF, USB Type-C® Cable Logo Usage Guidelines (Jan 2026): In order to pass through the USB-IF Compliance Program, all USB-C® to USB-C cables must be labeled using the appropriate data rate and power wattage cable logo. For example, a USB 20Gbps cable that supports 20V at 3A must be marked with the Combined Performance and Power 20Gbps/60W logo. usb.org/sites/default/files/usb_type-c_cable_logo_usage_guid…
  10. USB-IF, USB Type-C Cable and Connector Specification, Release 2.0 (August 2019): The following order of precedence of power negotiation shall be followed: USB BC 1.2 supersedes the USB 2.0 and USB 3.2 specifications, USB Type-C Current at 1.5 A and 3.0 A supersedes USB BC 1.2, and USB Power Delivery supersedes USB Type-C Current. usb.org/sites/default/files/USB%20Type-C%20Spec%20R2.0%20-%2…

Author: Bulan Sarkar · Report an error

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