I want to change my Apple Watch battery

You can check your Apple Watch's Battery Health in Settings > Battery > Battery Health. As a general rule of thumb, you should start to notice impacts when this number falls below 80%. If your Apple Watch battery isn't performing as expected, you can go to an Apple Store or Apple Authorized Service Provider for help with replacing your Watch's battery. This service costs $79 US, but prices vary by region. You can Contact Support to make an appointment at a store or send your Watch in for service.