Does a colouring app drain the battery or heat the phone?
Where the power actually goes in a colouring app, why the screen is almost the whole answer, and how to check your own numbers rather than trusting anyone else’s.
The short answer is that a colouring app is one of the cheaper things you can have on screen, and that almost all of what it does cost is the screen itself rather than the app. But that is worth unpacking, because it explains why two people get very different numbers from the same app.
Nothing here is a promise about your phone. It is a description of where the power goes, so you can work out your own case.
What the app actually asks the phone to do
Filling a region is a small amount of work: figure out which region you touched, change its colour, redraw that part of the picture. Between taps, nothing happens at all — no animation loop, no physics, no video decode. The processor spends most of a session idle.
Compare that with a game running a 60-frames-per-second render loop, or a video that has to decode every frame whether you are looking at it or not. Those keep the chip busy continuously. A numbered picture only wakes it when your finger lands.
The screen is nearly the whole bill
If the processor is mostly idle, what is left is the display, and the display is the single largest consumer on a phone during any activity where you are looking at a static image for a long time.
That is why brightness matters far more than which colouring app you use. Going from full brightness to about half typically changes power draw more than any difference between apps. On an OLED screen the picture itself matters too, because black pixels are genuinely off — a dark picture costs less than a bright one, and a mostly-white canvas is the most expensive thing you can look at.
When heat is worth noticing
Warmth during a long session usually is not the app. The common causes are charging while using the phone, a case that traps heat, direct sun, or something else running in the background — a download, a sync, a call.
The one case where a colouring app can generate real heat is loading: preparing a large, dense picture is a burst of work. That burst is short. If the phone gets hot and stays hot while you are just tapping regions, the cause is almost certainly elsewhere.
How to check your own numbers
Do not take anyone’s figure for this, including a general claim on a page like this one. Your screen, your brightness, your battery age and your picture all move the result.
- Note the battery percentage, then colour for a measured stretch — twenty minutes is enough to see a trend.
- Note it again. That difference is your real number, on your device, at your brightness.
- Repeat once at a much lower brightness. The gap between the two runs tells you how much of the cost was the screen rather than the app.
- Check the battery section in Settings afterwards, which attributes usage per app over the day.
Two runs is enough to answer the question for yourself, and the answer will be more useful than any general figure.
Where Numbrush fits
Numbrush does no continuous rendering between taps and makes no network calls while you colour, so a session’s cost is essentially the screen’s cost. Pictures are prepared once and stored on the device, which is where the brief bit of loading work happens.
Frequently asked questions
Does colouring use more battery than reading?
They are close, because both are mostly a static screen. Reading apps often use a dark background by default, which on OLED can make them cheaper. At the same brightness with a similar amount of light on screen, the difference is small.
Should I worry about screen burn-in from a static picture?
Sessions of tens of minutes are nowhere near the exposure that causes retention, and the picture changes as you fill it. Leaving any static image on screen for hours at maximum brightness is the case to avoid, and that is not specific to colouring.
Does colouring while charging damage the battery?
Using a phone while charging makes it warmer than either activity alone, and heat is what ages a battery. If it is getting noticeably hot, taking the case off or pausing the charge is the useful move.
Try it on a real canvas
Numbrush is colour by number for adults: mandalas, rose windows and geometric pattern work, twelve colours a picture, a magnifier for the tight spots, and a wrong tap that costs you nothing. Free, offline, no ads and no account.