Mac battery health checker

Updated 23 August 2026 · the command below was run in both zsh and bash on macOS 26.5.2 before this page went up. Who measures this.

Your Mac stores two different capacity numbers and shows you one of them, rounded. This prints both, in milliamp hours, next to the design capacity they are measured against. It needs no download, no password, and nothing leaves the machine.

The command

ioreg -c AppleSmartBattery -r -d1 -w0 | awk -F'" = ' '/^ +"[A-Za-z]+" = /{k=$1; gsub(/[ "]/,"",k); v[k]=$2} END{d=v["DesignCapacity"]+0; r=v["AppleRawMaxCapacity"]+0; n=v["NominalChargeCapacity"]+0; if(d==0||r==0){print "No internal battery found (desktop Mac?)"; exit} printf "Design capacity   %6d mAh\nRaw today         %6d mAh   %5.1f %%\nReported today    %6d mAh   %5.1f %%\nCycle count       %6d\nMaxCapacity key   %6d          <- a flag, not health\n", d, r, r/d*100, n, n/d*100, v["CycleCount"]+0, v["MaxCapacity"]+0}'

On the Mac this page was written on, that prints:

Design capacity	6249 mAh
Raw today	5301 mAh	84.8 %
Reported today	5453 mAh	87.3 %
Cycle count	548
MaxCapacity key	100	a flag, not health

System Settings on the same machine, in the same minute, says 87%. It is rounding the second number. The first one is not shown anywhere in macOS.

The key that fools almost everyone

MaxCapacity = 100 is not your battery's capacity. On Apple silicon it is a flag meaning the system considers the pack serviceable, and it reads 100 on a battery worn down to 84.8%, as it does above. Guides that tell you to divide MaxCapacity by DesignCapacity were written for Intel Macs, where that key really did hold milliamp hours. They were correct when they were written and are wrong on every Mac sold since 2020.

Why the popular command returns garbage

Search for this and you will be told to run ioreg -l | grep -i "MaxCapacity\DesignCapacity". It technically works and is unusable: inside the battery's BatteryData blob the same key names appear again without spaces around the equals sign, so grep drags out a two-kilobyte line of raw gauge data and the two useful lines drown in it.

The fix is one character of punctuation: search for " = " with the spaces, and the blob no longer matches. That is the whole reason the command "doesn't work" for people who try it.

What your number means, and what it doesn't

The two figures are not two attempts at one measurement. They are different quantities: the raw one is what the gauge currently estimates the pack holds, the reported one is what macOS is willing to show after its own smoothing. On this machine they sat 152 mAh apart today and on 15 August, and 308 mAh apart on 18 August, so the gap is not a constant you can subtract. Why your Mac reports two different health numbers takes that apart properly.

Read the whole number, not the decimals. Over a single session on this machine the raw capacity moved from 5270 to 5301 mAh, half a percentage point, as the charge and the temperature changed. The integer stayed at 84 through all of it.

Is your number normal for its mileage?

We collected 1539 pairs of "cycle count and health percentage" that people posted about their own Macs. Of the 441 machines with fewer than 50 cycles, the median was 99% and 225 of them were already below 100. The lowest was 77%. Nothing above 100 exists, so the only direction available from new is down, and it starts immediately.

Compare using the number System Settings shows you, not the raw one. The corpus was built from people reading System Settings, and mixing scales would put a healthy Mac below the average by arithmetic alone.

Questions people ask

Should I reset the SMC to fix a wrong battery percentage?

No. Apple silicon Macs have no separate SMC to reset, the key combinations from Intel-era guides do nothing at all, and the number is a measurement rather than a setting, so there is nothing in it to repair.

Does calibrating the battery help?

No. Deep discharge calibration applied to batteries Apple stopped shipping years ago. Draining to zero on a modern pack costs you a cycle and changes no reading.

Why does coconutBattery show a lower number than System Settings?

Any tool showing roughly two points less than macOS is reading the raw capacity instead of the reported one. Both numbers are real and both come from your battery. The forum answer that "one of them is buggy" is wrong in both directions.

The command printed "No internal battery found"

That is the guard, not a failure: an iMac, Mac mini or Mac Studio has no AppleSmartBattery to read. On a laptop, the same message would mean the pack is not being detected at all, which is worth a service appointment.