Battery Drain Test
Find out how fast your battery is actually draining — in percent per hour — with an optional bright-screen workload to speed up the measurement.
Leave this page open in the foreground. The rate updates as the battery level changes — the longer it runs, the more accurate.
How it works
The page reads your battery level through the browser's Battery Status API once per minute and fits a discharge rate over the elapsed time. If you plug in mid-test, tracking pauses and resumes when unplugged. The screen test adds a bright, animated fullscreen workload — the most power-hungry part of a phone — so you get a meaningful drain number in minutes instead of hours.
Everything happens on your device. Nothing is uploaded, and closing the page stops the test completely.
Frequently asked questions
How does this estimate battery drain rate?
The tool reads your device's battery level through the browser's Battery Status API every minute, tracks how fast the percentage drops while the page is open, and reports percent lost per hour. The screen test adds a controlled brightness workload so drain is measurable even on a resting device.
Is this accurate?
It's a real measurement, but browsers round battery level to whole percent steps, so on large batteries one percent can take many minutes. The estimate gets more accurate the longer you leave the page open. For precise capacity measurements, a native app like AccuBattery is better.
Why doesn't it work on my phone?
The Battery Status API is supported in Chrome, Edge, Samsung Internet, and most Android browsers. Firefox and Safari (including iPhone) removed battery access for privacy reasons, so this tool can't run there.
Does the screen test harm my battery or display?
No more than watching a video. The test shows a bright animated pattern for a fixed time, then stops. Modern OLED and LCD screens handle this fine — avoid leaving any bright static image for many hours, same as with any screen.
Can this tell me my battery's true health or capacity?
Not directly — browsers don't expose cycle count or design capacity. The drain rate is a practical proxy: if your phone drains much faster than it used to under similar conditions, the battery has likely degraded.