How to check your iPhone battery health

Battery health is the one condition question people most often get wrong, and not because they are guessing badly: the phone feels fine, so the number must be fine. It is worth thirty seconds to look, because 80 per cent is the line that matters to the price and the phone does not tell you which side of it you are on until you ask.

Open Settings, then Battery, then Battery Health and Charging. On older versions of iOS the last screen is called just Battery Health. The line you want is Maximum Capacity, shown as a percentage. That is the number the calculator asks for. 80 per cent or above is fine; under 80 is where the price changes.

What happens under 80: the phone moves from our Working grade to the middle grade, the one we call screen fine because the picture is fine, and it earns that price instead. The calculator shows you the difference for your model before you order, so there is no surprise later.

If the screen says Service, or there is a message about the battery being significantly degraded, that is Apple saying the same thing: the number is under 80. If it shows Unknown Part or no percentage at all, the battery has been replaced with one that is not an Apple part, or the phone cannot read it. Answer under 80 in that case and tell us in the notes. We measure every battery on the bench with our own equipment, so the number you give us is a starting point, not a promise you are held to.

One thing that catches people out: the percentage on the Battery screen is charge, how full the battery is right now. That is not battery health. A phone at 100 per cent charge can have a battery at 78 per cent health. Only the Maximum Capacity line on the Battery Health screen is the number we mean.

If the phone will not turn on, there is no way to read it, and that is fine. Pick the answer you believe and we will read the real figure when it arrives. We price the phone we actually receive, and an honest guess costs you nothing.