Why does my phone charge slowly through a PC?

Your phone is plugged into your computer, but the battery percentage barely moves. That can happen even when the cable fits and the phone says it is charging. A computer USB port often supplies less power than a wall charger, and the phone may reduce charging if it gets warm or its battery is nearly full.

Compare the charge rate from the PC and a wall charger under similar conditions. The Charger & Cable Test shows the phone's charging speed as a percentage per minute, if your phone's browser makes battery information available.

Compare charging from the PC and a wall charger

1. Open the Charger & Cable Test on the phone you want to check. Keep the test page open on the phone, not on the computer.
2. Connect the phone directly to a USB port on the PC. Avoid a hub, monitor port, or keyboard port for this first measurement.
3. Leave the phone idle for about 10 minutes, with the same screen brightness and apps open throughout. Start at a moderate battery level, such as 20% to 60%, rather than near empty or nearly full.
4. Note the charge rate shown by the test. Then connect the phone to a wall charger and repeat under similar conditions. Use the same cable if it fits both chargers.

The test compares the battery's reported percentage change over time. It does not measure the electrical power in watts or certify a charger. If the browser does not report battery information, the test may not be available on that phone.

What the result means

The phone charges much faster from the wall charger

The phone and battery can charge faster, but the PC port, cable, or USB connection is limiting the rate. Some computer ports supply only modest power, while certain ports are designed to provide more. A USB-C connector by itself does not guarantee fast charging. The phone, cable, and port all need to support a compatible charging method.

The charge rates are close

The PC port may be supplying about as much power as the wall charger, or the phone may be limiting both to a similar rate. A small difference is not always meaningful. Battery percentage changes in steps, and charging speed varies as the battery fills and warms up.

Neither connection charges quickly

The phone may be warm, near its charge limit, or using a cable that cannot support faster charging. A battery protection feature can pause or slow charging at a chosen level. Check the phone's charging settings before deciding that the port or battery is faulty.

The test does not show battery information

Some mobile browsers do not provide battery data to websites. That does not mean the phone is not charging. Check the phone's charging symbol and battery percentage instead, or repeat the comparison on a browser that reports battery information.

How to improve charging from a PC

1. Try another USB port. Connect directly to a port on the computer rather than through a hub or monitor. If the PC has a port marked for charging, try that one. Port capabilities vary, so the fastest-looking connector is not always the one that supplies the most power.
2. Use a cable that supports charging. Try a known-good cable that fits the phone and computer. A damaged cable, a loose connector, or a cable intended mainly for data can limit charging. Do not force a plug that does not fit securely.
3. Keep a laptop awake during the comparison. Some computers reduce or stop power to USB ports while asleep. In Windows 11, check Settings › System › Power & battery › Screen and sleep and keep the computer awake during the test. On a Mac laptop, check System Settings › Battery › Options for Prevent automatic sleeping on power adapter when the display is off, if available. Port behavior still depends on the computer.
4. Check the phone's charge limit. On iPhone, look under Settings › Battery › Charging for a charge limit or optimized charging option. On Android, look under Settings › Battery for charging optimization or a battery protection limit. The exact names vary by model. A limit or charging schedule can slow or pause charging even when the cable and port work.
5. Let a warm phone cool down. Heavy use, direct sunlight, or a thick insulating case can raise the phone's temperature. Stop demanding apps, move it out of the sun, and wait for it to cool before comparing charge rates again.
6. Use a wall charger when you need a faster charge. A PC port may not be designed to charge a phone quickly. Use a compatible charger and cable when you need a faster top-up, and follow the phone maker's charging guidance.

When the cable or port may be faulty

Repeat the comparison with a second cable and, if possible, another USB port. If the phone charges normally from a wall adapter but remains slow through one PC port with more than one known-good cable, that port may have limited output or a fault. If the phone charges slowly from several suitable chargers and cables, inspect its connector for visible debris or damage. Do not insert metal tools into the port. A loose connector, repeated interruptions, or unusual heat is a reason to stop using that connection and ask the device maker or a repair shop for help.

Why the same phone can charge at different speeds

Charging is not a fixed rate from start to finish. Phones commonly slow charging as the battery gets fuller or hotter. A PC may also share power among several connected devices, and its USB ports may behave differently when the computer is asleep or running on battery power.

For a fair comparison, test at roughly the same battery level, use the same cable where possible, and keep the phone idle in similar conditions. A percentage-per-minute result is useful for comparing setups, but it is not a precise measurement of the charger's wattage.