How much time does it take for an iPhone 11 to be fully charged?

Depends on the charging cable used.

Fast charge your iPhone and iPad

Use fast charge with certain iPhone or iPad models. You can recharge your iPhone up to 50 percent battery in around 30 minutes.

You can fast charge these iPhone and iPad models:

• iPhone 8, iPhone 8 Plus, and later
• iPad Pro 12.9-inch (1st generation and later)
• iPad Pro 11-inch (1st generation and later)
• iPad Pro 10.5-inch
• iPad Air (3rd generation)
• iPad mini (5th generation)

With iPhone, you can fast charge up to 50 percent battery in around 30 minutes.*

Fast charging works when you use an Apple USB-C to Lightning cable and one of these adapters:

• Apple 18W, 29W, 30W, 61W, 87W, or 96W USB-C Power Adapter
• A comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD)

If you're not sure which Apple Power Adapter you have, check the wattage on the bottom of the adapter:

Protect & Prolong life of your iPhone's Battery:

1. About the battery usage on your iPhone, iPad, and iPod touch ...
2. Batteries - Maximising Performance - Apple (IN)
3. iPhone Battery and Performance