Will It Work? · Guide
Laptop charging over USB-C: what the watts on the adapter mean
By Bulan Sarkar, founder of ElectronicsInfoline (since 2000)
A laptop spec sheet can carry three different wattages: the adapter in the box, a minimum the maker recommends, and the charger size for fast charging. They answer different questions. This guide sets them side by side from the makers' own pages, then shows what a USB-C cable adds to the picture.
The watts on a USB-C laptop adapter are the most it can give. The laptop takes what it asks for, up to that figure. Makers print up to three numbers: the adapter in the box, a minimum recommended wattage, and a fast-charge figure (for one 14-inch laptop, 60 W and 96 W). A bigger USB PD adapter is fine. A smaller one still charges a Mac, Apple says, just not at its best. Above 60 W the cable must be a 5 A one.
The three numbers on a laptop spec sheet
Here is what four laptop pages say, copied from the makers. On the first row, the adapter in the box is below the fast-charge figure on the same page.
| Laptop (maker page) | In the box | Minimum recommended | Fast charge |
|---|---|---|---|
| MacBook Air 13-inch (M5) | US: 40 W adapter, 60 W max (Apple) India: 30 W or 35 W dual-port (Apple) | not stated | 70 W or higher USB PD |
| MacBook Pro 14-inch (M6) | see the maker's page for your country | 60 W (Apple) | 96 W or higher USB PD (Apple) |
| MacBook Pro 16-inch (M5) | see the maker's page for your country | differs by chip; see the page | 140 W or higher USB PD (Apple) |
| ThinkPad X1 Carbon Gen 12 | 45 W or 65 W USB-C, PD 3.0 (Lenovo) | not stated | Rapid Charge to 80% in 1 hour with the 65 W adapter (Lenovo) |
The fast-charge figure is the smallest charger that unlocks the fast mode. It is not what the laptop draws, and none of these pages gives that number. Lenovo adds a condition to its own figure: Rapid Charge is only guaranteed with the laptop off, in standby or hibernating; while it runs, charge time depends on what the system is using and on the adapter (Lenovo).
A bigger or smaller adapter: what happens
A USB Power Delivery charger does not push its full rating into the laptop. It offers a set of voltages, and the laptop picks one. A higher-rated charger also offers the lower levels, so it looks like a smaller one to a device that wants less (USB-IF). That is why a 96 W adapter is safe to use on a laptop whose fast-charge figure is 70 W.
Apple puts it plainly for its USB-C laptops: any USB PD adapter or display can charge them (Apple), even one with higher or lower wattage than the adapter it recommends (Apple). The India support page says the same (Apple). The next line adds a condition: for the best charging experience, use at least the minimum wattage it recommends (Apple). Below that, you are in the red band of Figure 1.
The box differs by country; the figures do not
The same 13-inch laptop ships with a 40 W adapter (60 W max) on the US page (Apple) and with a 30 W or 35 W dual-port adapter, depending on the chip, on the India page (Apple). Both pages give the same fast-charge figure, 70 W or higher. Lenovo's sheet says its adapter offerings depend on the country (Lenovo).
So read the spec page for the country you bought in. Someone online who says their laptop “came with” a given adapter may be right for their country and wrong for yours.
The cable decides the ceiling
Below 100 W, USB PD tops out at 20 V. A standard USB-C cable is rated for 3 A, so at 20 V it carries 60 W; an electronically marked cable is rated for 5 A (USB-IF), which gives 100 W at 20 V. Any cable rated above 3 A must carry that marking (USB-IF).
Above 100 W, the charger has to switch to one of the extended-range voltages, starting at 28 V (USB-IF), and the cable must be a 240 W one (48 V, 5 A) (USB-IF). On the figures in the table: a 60 W minimum fits any USB-C cable; 65, 70 and 96 W need a 5 A cable; 140 W needs the 240 W cable.
Check what you are getting
The adapter's own label lists its wattage. On a Mac you can also read what the connected adapter gives: hold Option, open the Apple menu, choose System Information, select Power, and look under AC Charger Information (Apple). If that number is lower than the adapter's label, suspect the cable first.
To read an adapter label line by line, see how to read a charger label. To check one adapter, cable and laptop together, use the charger and cable checker; its maker presets include these laptops.
Tips and tricks
- Read the spec page for your own country. The adapter in the box can differ even when the model name is the same.
- If you buy one adapter for the laptop, buy it at or above the fast-charge figure (70 W for the 13-inch laptop above). A smaller one charges, but not in the fast mode.
- Above 60 W, check the cable says 100 W, 5 A or 240 W. Count a cable with no rating on it as a 3 A one.
- A higher-watt adapter can be shared with a phone. It offers the lower voltages too, and the phone asks for the one it wants.
- Lenovo only guarantees its Rapid Charge figure with the laptop off, in standby or hibernating. Charging while you work takes longer.
- After plugging in a new adapter on a Mac, open System Information → Power and read AC Charger Information. That is the number to compare.
What we would do
Find your laptop's spec page for your country and write down two numbers: the minimum recommended wattage (if the maker gives one) and the fast-charge figure. Buy a USB PD adapter at or above the fast-charge figure, and a cable rated for its current: 5 A for anything over 60 W, 240 W for anything over 100 W.
A smaller USB-C adapter you already own still charges a USB-C Mac, by Apple's own support page. Keep the full-size one for days when you need the battery back quickly. Then put the adapter label, cable and laptop into the charger and cable checker to see the watts you will get.
Questions people ask
Can I charge my laptop with a higher-watt USB-C charger? Yes. A USB Power Delivery charger offers a list of voltages and the laptop asks for the one it wants, so a 96 W charger on a laptop that needs less simply gives less. Apple's support page says a Mac charges from any USB PD adapter, even one with higher or lower wattage than the one it recommends.
Can I charge a laptop with a lower-watt USB-C charger, like a phone charger? Apple's support page says yes for its USB-C laptops, even below the recommended wattage, and adds that for the best charging experience the adapter should give at least the minimum it recommends. For the 14-inch model on this page that minimum is 60 W.
What does "fast-charge capable with 70W or higher USB PD power source" mean? It is the smallest charger the maker names for the laptop's fast-charge mode. Below 70 W that laptop still charges, just not in that mode. The page gives no figure for what the laptop draws while it charges.
Why does my laptop charge at only 60 W from a 100 W charger? Check the cable first. At 20 V a standard USB-C cable is rated for 3 A, which is 20 × 3 = 60 W. Anything above that needs an electronically marked 5 A cable (100 W at 20 V), and above 100 W the charger and cable must support the 28 V extended range.
How do I see how many watts my charger is giving my Mac? Hold the Option key, open the Apple menu, choose System Information, then select Power. Apple says the wattage is listed under AC Charger Information.
Why did my laptop come with a smaller charger than the same model elsewhere? What ships in the box can change by country. One maker's US page lists a 40 W adapter (60 W max) for its 13-inch laptop, while its India page lists 30 W or 35 W depending on the chip. Another maker's spec sheet says its adapter offerings depend on the country.
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.
- Apple, MacBook Air (M5), Technical Specifications:
40W Dynamic Power Adapter with 60W Max USB-C to MagSafe 3 Cable (2 m) Fast-charge capable with 70W or higher USB PD power source
apple.com/macbook-air/specs/ - Apple, MacBook Air (M5), Technical Specifications (India):
30W USB-C Power Adapter (included with M5 with 8-core GPU) 35W Dual USB-C Port Power Adapter (included with M5 with 10-core GPU; configurable with M5 with 8-core GPU) USB-C to MagSafe 3 Cable (2 m) Fast-charge capable with 70W or higher USB PD power source
apple.com/in/macbook-air/specs/ - Apple, MacBook Pro, Technical Specifications:
Supports charging via a USB‑C power adapter or other USB PD power source Minimum wattage recommended to charge the device: 60W Fast-charge capable with 96W or higher USB PD power source
apple.com/macbook-pro/specs/ - Apple, MacBook Pro, Technical Specifications (India):
Supports charging via a USB‑C power adapter or other USB PD power source Minimum wattage recommended to charge the device: 60W Fast-charge capable with 96W or higher USB PD power source
apple.com/in/macbook-pro/specs/ - Apple, MacBook Pro 16-inch, Technical Specifications:
Fast-charge capable with 140W or higher USB PD power source
apple.com/macbook-pro/specs/ - Apple, Use a power adapter with your Mac (Apple Support):
If your Mac uses USB-C to charge, you can charge your Mac laptop with any USB-C power adapter or display that supports USB Power Delivery (USB PD).
support.apple.com/en-us/109509 - Apple, Use a power adapter with your Mac (Apple Support):
you can charge your Mac with any USB-C power adapter or display, even if it provides higher or lower wattage than the adapter recommended for your Mac.
support.apple.com/en-us/109509 - Apple, Use a power adapter with your Mac (Apple Support), India:
you can charge your Mac with any USB-C power adapter or display, even if it provides higher or lower wattage than the adapter recommended for your Mac.
support.apple.com/en-in/109509 - Apple, Use a power adapter with your Mac (Apple Support):
For the best charging experience, use a power adapter or display that provides at least the minimum wattage of the power adapter recommended for your Mac.
support.apple.com/en-us/109509 - Apple, Use a power adapter with your Mac (Apple Support):
Select Power in the sidebar, then scroll down on the right to find the wattage listed under AC Charger Information
support.apple.com/en-us/109509 - Lenovo, ThinkPad X1 Carbon Gen 12, PSREF specifications:
45W USB-C® (2-pin) AC adapter, supports PD 3.0, 100-240V, 50-60Hz • 45W USB-C® (3-pin) AC adapter, supports PD 3.0, 100-240V, 50-60Hz • 65W USB-C® (2-pin) AC adapter, supports PD 3.0
psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad_X1_Carbon… - Lenovo, ThinkPad X1 Carbon Gen 12, PSREF specifications:
AC adapter offerings depend on the country.
psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad_X1_Carbon… - Lenovo, ThinkPad X1 Carbon Gen 12, PSREF specifications:
57Wh Rechargeable Li-ion Battery, supports Rapid Charge (charge up to 80% in 1hr) with 65W AC adapter
psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad_X1_Carbon… - Lenovo, ThinkPad X1 Carbon Gen 12, PSREF specifications:
Rapid charge is only guaranteed when the computer is turned off or in standby mode or in hibernation mode. When the computer is powered on, the Charge Time will vary depending on system power consumption and AC adapter power.
psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad_X1_Carbon… - 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.… - USB-IF, USB Developer Days 2019: USB Power Delivery:
Capability is incremental; higher rated Sources also look like lower rated Sources
usb.org/sites/default/files/D2T2-1%20-%20USB%20Power%20Deliv… - 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… - 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… - 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…