postcrete

Hi all does anyone know how much postcrete I would need for a 20litre bucket? Thank you!

Ok I've replaced several 9ft high posts, 4" × 4" into concrete. My gawd it nearly killed me removing the old posts. I've attached a photo of the posts set in postcrete. Now they are in the same position as the ones I removed. 2ft of the posts are buried in 12" diameter holes. I've measured 2.8m...