What battery calibration actually is
Battery management uses a System Management Controller (SMC) chip to track charge/discharge cycles. Over time, the SMC's estimate of 'full capacity' can drift from reality.
Calibration is the process of resetting that estimate by running a full charge → full discharge cycle. The battery itself isn't being repaired — just the software estimate.
Apple Silicon (M-series) — do you need to calibrate?
No — Apple Silicon Macs (M1, M2, M3, M4) have dynamic battery management that auto-recalibrates continuously. You don't need to do anything.
If your battery health % seems wrong, it's almost certainly a real degradation issue, not a calibration drift. Don't waste time on manual calibration — book a battery service or accept the reality.
Intel Macs (2009–2019) — calibration still relevant
Older Intel Macs benefit from calibration every 1–3 months. Procedure: charge to 100%, leave plugged in 2 hours, unplug and use until shutdown, leave off 5+ hours, charge fully.
Don't do this more than once a month — full discharges age the cells faster than necessary.
When manual calibration helps even on Apple Silicon
Battery shows wildly inaccurate percentage drops (e.g., 50% → 5% → 30% during use). This is rare but happens after macOS updates.
Reset procedure: hold the power button 10 seconds to force off → leave off 5 minutes → power on. This forces SMC re-read of battery status.
When calibration won't help — accept the reality
Battery health below 80%: the cells are physically degraded. Calibration doesn't recover capacity. Time for battery replacement.
'Service Battery' warning in System Settings: physical issue. Service it.
Sudden shutdowns at 30%+ remaining: battery cell or BMS hardware failure. Service or replace.
Best practice for battery longevity
Don't keep at 100% constantly when plugged in for weeks. Apple Silicon helps with Optimised Charging — turn it on (System Settings → Battery → Health → Optimised Charging).
Don't deplete to 0% regularly. Lithium cells age faster below 20% than at any other charge level.
Avoid extreme temperatures. Don't leave Mac in car in summer or store in unheated garage in winter.