Charging Wattage Calculator
Your device and your charger both have limits. The slower of the two sets the speed; this tool shows the result.
Estimates assume an average 78% end-to-end efficiency and the normal slowdown after 80%. Real results vary with temperature, cable quality and use while charging.
About the Charging Wattage Calculator
Fast charging is limited by whichever is weaker: the charger or the device. This calculator pairs your iPhone, iPad or Mac with any USB-C charger wattage and shows the speed you will actually get, plus whether a cable upgrade matters.
How to use it
- 1 Pick your device.
- 2 Enter your charger wattage (printed on the adapter).
- 3 See the effective charging speed and the bottleneck.
Frequently asked questions
Does a 96W Mac charger charge my iPhone faster?+
No faster than the iPhone limit. Recent iPhones peak around 25 to 30W wired; the device only draws what it can use, and the big charger is safe to use.
Why does charging slow down after 80 percent?+
By design: lithium batteries charge fast when empty and taper near full to protect lifespan. The last 20 percent can take as long as the first 50.
Do all USB-C cables charge at full speed?+
No. Standard cables cap at 60W; high-power Mac charging needs a 100W or 240W rated cable. For iPhones any decent USB-C cable is enough.
