You’re working on your laptop, and suddenly the battery warning pops up. All you have nearby is your phone charger. Naturally, you wonder, “Can I just use this to charge my laptop?” It’s a common question, especially when you’re traveling or caught off guard. Before you plug your phone charger into your laptop, it’s important to understand what happens behind the scenes.
This article explains whether a phone charger can supply enough power for a laptop, the key differences between phone and laptop chargers, potential safety issues, and which chargers and cables actually work together. By the end, you’ll be equipped to charge your devices safely and effectively.
Can a Phone Charger Provide Enough Power to Charge a Laptop?
The short answer is usually no, at least not efficiently.
Laptop batteries are much larger than phone batteries. While a typical smartphone battery ranges from about 3,000 to 5,000 mAh (milliamp hours), laptop batteries often exceed 40,000 mAh, depending on the model and size. This means laptops require significantly more power to charge properly.
Power Output Differences
Charger power is measured in watts (W), calculated by multiplying voltage (V) by current (A). Most phone chargers provide between 5 and 20 watts. Common chargers supply 5W or 10W, while fast chargers can reach 18W, 20W, or sometimes up to 30W.
Laptop chargers, on the other hand, typically range from 45 watts up to 100 watts or more, especially for gaming laptops and powerful ultrabooks.
Here’s a quick comparison:
| Device Type | Typical Charger Wattage |
|---|---|
| Smartphone | 5W – 30W |
| Ultrabook Laptop | 30W – 60W |
| Standard Laptop | 65W – 90W |
| Gaming Laptop | 90W – 240W+ |
If your laptop charger is 65W and your phone charger only outputs 20W, charging will be very slow, or the laptop might even use more power than the charger can supply, causing the battery level to drop despite being plugged in.
USB-C and Power Delivery (PD)
USB-C combined with the Power Delivery (PD) standard has transformed charging capabilities. Some newer phone chargers with PD can deliver up to 100 watts, matching many laptop chargers.
For example, Apple’s 96W USB-C charger can power a MacBook without issues. However, most phone chargers—especially standard 18W or 20W bricks—do not output enough power for typical laptops Source: USB Implementers Forum.
What Are the Differences Between Phone and Laptop Chargers?
Understanding these differences helps explain why phone chargers usually don’t work well with laptops.
Voltage and Current
- Voltage (V): The electrical “pressure” pushing current through the device.
- Current (A): The amount of electric charge flowing.
Phone chargers commonly supply 5V, sometimes increasing to 9V or 12V with fast-charging technologies. Laptop chargers generally provide 19V or higher. Modern USB-C PD chargers can adjust voltage dynamically (5V, 9V, 15V, 20V) based on the device’s requirements.
If a laptop expecting 19V receives only 5V, it may charge slowly or not at all Source: Intel USB Power Delivery Overview.
Connector Types
Older laptops use proprietary barrel connectors, making phone charger cables incompatible. Newer models often feature USB-C ports that support charging. Phones typically use USB-C or Apple’s Lightning connector.
Physical compatibility matters: even if the charger can supply enough power, the connector must fit your laptop’s charging port.
Communication Protocols
Chargers and devices “negotiate” power delivery through communication protocols. This handshake ensures the charger supplies the correct voltage and current. If the negotiation fails, the charger defaults to the lowest power output, which might not be enough to charge a laptop.
Is It Safe to Use a Phone Charger for a Laptop?
Safety is a valid concern when mixing chargers and devices.
Could It Damage Your Laptop or Charger?
Generally, using a lower-wattage phone charger with a laptop will not damage either device. Most laptops will simply charge very slowly or maintain battery level instead of charging.
However, problems can arise if you use incompatible chargers or cables. For example, forcing a charger with the wrong voltage or a non-certified cable could cause overheating or damage Source: Consumer Reports.
Battery and Performance Impact
Using an underpowered charger may cause your laptop to run at reduced performance because it’s drawing power from both the charger and its battery, leading to faster battery drain over time.
When Is It Safe?
- If your laptop supports USB-C charging and the phone charger supports USB Power Delivery with sufficient wattage (ideally 45W or more), it’s generally
Danny Inayat