How to test a USB-C to USB-A charging cable
Compare a USB-C to USB-A cable with another cable, spot slow charging, and learn what a browser test can and cannot tell you.
Your phone or other device charges slowly, and you are not sure whether the cable is the cause. A USB-C to USB-A cable can charge a device, but the result also depends on the charger, the device, and what it is doing while plugged in.
Compare the cable under the same conditions with the Charger & Cable Test. It measures the change in battery percentage per minute, which helps you compare charging combinations. It does not measure electrical power in watts or certify the cable.
Test the cable
- Open the Charger & Cable Test on the device you want to charge. The test appears only on devices whose browser reports battery information. If it is missing, the browser cannot provide the data needed for this test.
- Use a compatible USB-A wall charger and connect it to the device with the USB-C to USB-A cable. Check that the device itself shows that it is charging.
- Keep the device in a similar state for each comparison. Let it cool if it is warm, close demanding apps, and avoid using it while it charges. Start with a similar battery percentage each time, preferably somewhere in the middle rather than near full.
- Read the charging speed in percent per minute. Repeat the check with a known-good USB-C to USB-A cable, keeping the same charger, device, outlet, and conditions. Change only the cable so the comparison is useful.
Battery percentages update in steps, so a brief reading can jump around or show no change. Give each comparison several minutes and repeat it if the readings differ. A browser test may not be available on every phone, even if the phone itself can show its battery level.
What the result means
The test shows a steady charging rate
The device is receiving charge, and you have a useful baseline for this specific charger and cable combination. Compare the number with another cable under similar conditions. A higher result does not prove that the cable meets a particular USB speed or power rating.
The rate is lower with this cable
If the same device and charger charge faster with a known-good cable, the cable may be damaged, poorly made, or unable to support the charging method the device and charger can use. Try another USB-A port or charger before deciding the cable is at fault.
The rate is low with both cables
The charger, outlet, device, heat, or background activity may be limiting charging. Some devices also slow charging as the battery gets full or warm. Compare at a similar battery percentage and temperature before drawing a conclusion.
The device does not show that it is charging
The test cannot establish that the cable is delivering power if the device does not detect charging. Reseat both connectors, try a different USB-A port or charger, and inspect the cable for damage. Stop using it if a connector is loose, unusually hot, bent, or scorched.
How to troubleshoot a slow result
- Check the charging indicator. Confirm that the device recognizes the connection, rather than assuming the cable is charging because it is plugged in. On Windows 11, check Settings › System › Power & battery. On macOS, open System Settings › Battery. On iPhone, open Settings › Battery. On Android, open Settings › Battery, though the exact menu can vary by manufacturer.
- Reseat the connectors. Unplug the cable at both ends and reconnect it firmly. Check the USB-C port for lint or debris, but do not insert metal objects or force the connector.
- Try another USB-A port or charger. If the result improves, the original port or charger may be the limiting part. Use a charger that is compatible with your device, and stop if the charger or cable becomes unusually hot.
- Reduce the device's workload. A bright screen, video, games, or other demanding apps can use some of the incoming power. Let the device sit idle and cool, then compare again.
- Compare with a known-good cable. Keep the device, charger, outlet, and approximate battery percentage the same. If only one cable repeatedly charges more slowly, replace it rather than relying on a single short reading.
When the cable may be faulty
A cable is a stronger suspect if charging repeatedly stops when it is gently moved, the connector fits loosely, or the same charger charges faster with another cable. Do not bend or wiggle a damaged cable to keep it working. Replace it, especially if you see exposed wires, a split jacket, corrosion, or heat damage. If multiple known-good cables fail with the same charger, test a different compatible charger or have the device's charging port checked.
What this test cannot tell you
Percent per minute is a comparison, not a wattage measurement. Battery percentage is rounded, and charging speed changes with battery level, temperature, and the device's charging controls. A USB-C to USB-A cable also does not provide USB-C Power Delivery from a USB-C charger, because its charger end is USB-A. Some USB-A chargers and cables support other fast-charging methods, but the device, charger, and cable must all support the same method to use it.
Use the test to find a repeatable difference between cable and charger combinations, not to prove a cable's advertised rating or electrical safety.
