iPhone Charging Speed Test: Why It Gets Hot

Test your charging speed

Add Charging to your dashboard from Edit Dashboard (Pro), plug in a charger, open the card. It samples your battery level every 5 seconds; once it has at least two readings, Rate: becomes the percentage gained divided by the minutes elapsed, averaged over the last six samples - about 30 seconds of data.

Open Device Monitor, tap the slider icon on the Monitor tab and add Charging to your dashboard.
Plug your iPhone into the charger you want to test.
Open the Charging card and wait at least 30-60 seconds so it has enough samples.
Read Rate: (%/min) and the coloured speed label next to Est. Watts.
Check Time to Full for how long is left at the current rate.

Two real chargers compared, from the same battery-level-per-time formula the app uses
Charger	Battery change	Rate	Speed	Est. Watts	Time to full
Fast charger, battery at 37%	35% to 37% in 50 s	2.40 %/min	Fast Charging	~30W	~26 min
Slower charger, battery at 91%	90% to 91% in 110 s	0.55 %/min	Normal Charging	~3W	~16 min

Notice the second case still shows a short Time to Full: it only has 9 percentage points left to go, so even a slow 0.55%/min rate finishes quickly. A fast charger reads clearly above 1.5%/min and flips the label to "Fast Charging"; a basic 5 W charger usually stays under 0.5%/min ("Trickle Charging").

Check whether the heat is normal

The free Thermal State row (in Device Info, or live with Pro's Thermal Monitor) reports one of four iOS states - Normal, Elevated, Serious or Critical - never a number of degrees, because iOS simply does not hand apps a real temperature.

Normal: nothing to worry about, even if the phone feels warm to the touch.
Elevated: warmer than usual; charging and normal use still work, but the phone is managing heat.
Serious: it is actively cooling itself and may slow charging or performance to do it.
Critical: it will stop charging and may show its own warning; let it cool before using it.

Worked example: a charge that slows down because it got hot

Two snapshots of the same charging session, a few minutes apart
Moment	Battery change	Rate	Speed	Thermal State
Early (phone cool)	50% to 51% in 90 s	0.67 %/min	Normal Charging	Normal
After getting warm	72% to 73% in 300 s	0.20 %/min	Trickle Charging	Serious

This is the pattern behind most "why is my phone hot and barely charging" moments: once the thermal state rises, iOS deliberately slows the charge rate (sometimes performance too) to bring the temperature back down. The rate falling from 0.67 to 0.20%/min while the thermal state moves from "Normal" to "Serious" is the phone protecting itself. Not a fault.

Reading Est. Watts honestly

Why your result may look slow or run hot

iOS reports battery level in whole 1% steps, so right after plugging in the rate can look off until a couple of minutes of real data build up.
Charging slows on purpose above roughly 80% to protect the battery - a trickle rate near full is expected, not broken.
Using the phone while it charges (gaming, video calls, navigation) piles the processor and screen's own heat on top of the charging heat.
A thick case, direct sunlight, or a wireless pad (less efficient than a cable) all push the thermal state higher, faster.
A cable, adapter or port that doesn't support fast charging caps the rate no matter what the phone itself is capable of.

Free vs Pro

Thermal State is free, living in Device Info and the widget. The live Thermal Monitor graph and the whole Charging Analyzer card - Rate, speed label, Est. Watts, Time to Full, Charge History graph, Charging Stats after a few sessions - sit behind Pro. A quick read of whether things look normal right now? The free row usually covers it. Watching the trend while it charges is what the Pro cards are actually for.

Questions and answers

What is a normal iPhone charging speed app reading?

Above about 1.5%/min counts as Fast Charging, 0.5-1.5%/min as Normal Charging, under 0.5%/min as Trickle Charging. Expect the rate to drop once the battery passes 80% - that's normal, not a sign your charger is failing.

Why isn't my iPhone fast charging?

Check that the cable, the adapter and the port all support fast charging - a Fast Charging result needs every one of the three. A battery above roughly 80%, a hot phone, or heavy use while it charges will also slow the reported rate even with the right hardware plugged in.

Is it normal for an iPhone to get hot while charging?

Yes, in most cases. Charging current generates heat as a normal side effect, more so with fast chargers, and it climbs if you use the phone, leave a case on, or charge somewhere warm. Thermal State sitting at Normal or Elevated while the phone feels merely warm is typical, nothing to worry about.

Why does my iPhone get hot while charging wirelessly?

Wireless charging loses more energy to heat than a cable does for the same charge rate, since it's simply less efficient. It's common for the Thermal State to reach Elevated sooner on a wireless pad than it would on a cable.

How long does it take to fully charge an iPhone?

Depends on the charger and the starting level, which is exactly what Time to Full in the Charging Analyzer estimates from your current rate. As a rough guide, a fast charger from a low level often finishes well under an hour, then slows considerably through the last 20%.

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