@dme2 Hi dme2, I’m building three connected domes in Longreach, Qld and I did calculation. I actually wanted to know how many blocks I’d need to make and could work out the amount of concrete. I’ll use one of my domes ok. Bedroom radius is 2250mm The surface area of a sphere: 4xpi x radius squared. So surface area is 4 x (22/7) x (2250 x2250) or 63,643,857. I need half a sphere (31,821,429) PLUS the part of a hemisphere enclosed by the height of the centre pole I’m using (900mm), ie 900/2250 of a hemisphere: 12,728,572. The total surface area I have to cover is: 43,550,001sq mm. My blocks measure 220x330mm. Total area 72,600sqmm. So number of blocks is 44,550,001 /72,600 Thats 600 blocks. I can make 70 blocks per pour using 6.2 bags. That’s 9 pours And 55 bags of cement. The numbers just look scary. Good luck