charger
Whats a safe size charger to buy for iphone 11
iPhone 11
Question marked as
Any size. You can use the 5 watt power adapter and cable from an older iPhone if you have them. If you want to fast charge you will need an 18 watt or larger. See: Fast charge your iPhone - Apple Support
As noted in that support article you can use larger power adapters such as the 140 watt. The iPhone won't draw more power than it is designed to.
One very commonly used power adapter is: Buy 20W USB-C Power Adapter - Apple