The border radius is the distance from the middle of the button to the bounding surface of a button. The border radius is adjustable.
This procedure is applicable in both themes 2.0 and 3.0.
To alter the border radius of buttons, follow these simple steps:
STEP 1. Go to your Shopify Admin, under Sales Channels, select Online Store.
STEP 2. On the right portion of the page, click on Customize.
STEP 3. Located on the bottom part of the sidebar menu, tap Theme settings.
STEP 4. Tap Advanced Settings.
STEP 5. Move the slider to your desired border radius.