Slate Gravel to cover front lawn

[gandan]

Hi, newbie to the forum but does anyone know roughly how many of the large builder bags(1 ton) I will need to cover a front garden 6 x 4 x whatever depth I need. I am going to dig up my mother in laws lawn and she wants low maintainence with slate/gravel and a circular slab arrangement. I am unsure what is the recoimmended depth to go down before putting the membrane down and covering it. Its well compacted, been left there for donkeys. Thanks for any advice

 

[JHook]

General rule of thumb ton bags cover roughly 11 sq m @ 2" that should be deep enough, so you would have surplus even @ 3" depth. Ask if the supplier does smaller or self fill bags

 

[Nick98]

Just to note to say that if you are calculating it then a dumpy bag from a builders merchant is normally only 850kgs and not a ton. I was caught out a couple of times a while ago as I couldn't work out why I didnt have enough - until the merchants pointed it out!!