So I've been digging an area out for a shed/ summer house base and trying to get a decent idea for the required material is a nightmare. Many sites gave my a rough idea but this figure varied between 3.5 - 5.8 bags of ballast. So I'm going to explain my situation and hopefully you can work out roughly whats required. This is what happened. Area: 7m x 3.3m x 100mm Volume: 2.34 meters3 I ordered: 3 x Bulk Bags of Ballast (800kg Bulk) 39x Bags of 25kg bag of cement. For a 13 cement per bulk bag of ballast (advice found on B&Q website) I filled half the area using 3 x bulk bags of ballast & 17 bags of cement. So... I actually needed: 6 x Bulk Bags of Ballast (800kg Bulk) 34x Bags of 25kg of cement. I would advise to slightly over order on cement just incase you use more in each shovel load. BUT, by way of ballast, 6 bulk bags is a definite for that area. So thats 4.8 Tonnes of ballast to fill an area of 2.34 m3. 850 kg of cement. 5650 kg (5.65 Tonne) of material total. I hope that all makes sense. Do the math yourself, but I will be going off 2.3 Tonnes of Ballast for every 1m3.