Example based on 10mm joint width, 24mm deep.

Paving Size/mm 20KG Bucket 12KG Bucket
600 x 600 12.5m² 7.5m²
600 x 450 10.5m² 6.3m²
450 x 450 9m² 5.4m²
300 x 450 7.5m² 4.5m²
300 x 300 5.5m² 3.5m²

All quoted coverages are approximates.