Because this is so infuriatingly difficult to find on Shopify website!
//

pico: 6 × 16

icon: 32 × 32

thumb: 50 × 50

small: 100 × 100

compact: 160 × 160

medium: 240 × 240

large: 480 × 480

grande: 600 × 600

1024x1024: 1024 × 1024

2048x2048: 2048 × 2048

master: (original)

//
example usage:
<img src="{{ image.src | img_url: 'grande' }}" alt="{{ image.alt | escape }}">