I copied this to my notes when I was lookin for lights, hope it’s helpful
Here’s a quick reference guide to use as a starting point:
Grow LightClosest~ SunlightFurthest
150W 8″ (20cm) 10″ (25cm) 12″ (30cm)
250W 10″ (25cm) 12″ (30cm) 14″ (35cm)
400W 12″ (30cm) 14″ (35cm) 19″ (48cm)
600W. 14″ (35cm) 16″ (41cm) 25″ (64cm)
1000W 16″ (41cm) 22″ (55cm) 31″ (79cm)
150W – covers 2′ x 2′ (0.6m x 0.6m) area
250W – covers 2′ x 2′ (0.6m x 0.6m) area up to 2.5′ x 2.5′ (0.8m x 0.8m)
400W – covers 3′ x 3′ (0.9m x 0.9m) area up to 3.5′ x 3.5′ (1m x 1m)
600W – covers 3.5′ x 3.5′ (1m x 1m) area up to 4′ x 4′ (1.2m x 1.2m)
1000W – covers 4′ x 4′ (1.2m x 1.2m) area up to 5′ x 5′ (1.5m x 1.5m)