Can I make my iPhone vibrate louder or stronger?

No, you can’t make your iPhone vibrate louder. But since your real issue is that you’re not noticing the vibration while it’s in your pocket, you could try creating a custom vibration that is more noticeable to you.

Creating a custom vibration

Follow these steps:

1. Open Settings
2. Tap on Sounds
3. Tap on the Ringtone option
4. Tap on Vibration
5. Tap on Create New Vibration
6. Now tap the centre of your screen to record a pattern you think will be more noticeable (I’m thinking two or three long presses will be more obvious when it’s in your pocket, but at least you can try different things until you find one that suits you)
7. When finished, tap on Save in the top right-hand corner
8. Give your new custom vibration a name
9. Make sure it’s now selected as your vibration type for your ringtone
10. Exit Settings

Note: - All vibrations you create appear in a list of custom vibrations and are available for all events, not just your ringtone (e.g. you can select it for reminders, texts, etc).

[EDIT - Select or create custom vibrations for individual Contacts]

Another option that may interest you is to select or create a custom vibration for people in your contacts. To do this:

1. Open Contacts
2. Select a contact
3. Tap on Edit in the top right corner
4. Tap on either Ringtone or Text Tone
5. Tap on Vibration
6. Select one of the standard or custom vibrations
7. Go back and tap on Done