How to calculate the quantity of materials for mortar and Ytong stones?

Hello,
Assuming you want to build a small garden shed measuring 6m x 4m (and 2.40m height - without roof yet) on an existing base plate with Ytong (Ytong plan blocks 499x365x249mm) and later install a roller door (2632x2405) and a window (50x100cm).

Question:
- How do I calculate, for example, how much mortar and Ytong blocks I need? I would then have to factor in how thick the mortar joints are.
- How large should the door and window openings actually be after masonry to properly install the door and window? Would you simply calculate 2-3 cm more opening for sealing work?

Look at the manufacturer’s specifications. The yield is indicated for every mortar (or adhesive). And there are installation instructions for the window and door as well. The number of bricks is then determined by the openings. But some materials are still missing? Concrete+steel for the ring beam, roof and drainage, moisture barrier.... And really 36.5 Ytong?! Isn’t that a bit much?

Thanks first for the reply. I had considered between Ytong and sand-lime brick. Sand-lime brick seems more difficult to work with. Ytong is comparatively easier. Since the garage will be built directly on the neighbor's boundary (corner area of two neighbors) and might also be worked on there with sawing, drilling, etc., I wanted to choose a somewhat higher bulk density material (for sound insulation). Therefore, I would currently tend towards the 36.5 cm version. Then, I think, it is also easier to subsequently drill wall shelves or similar.

I wanted to assign the roof separately to a roofer. I only dare to do the masonry if I really deal with it and research thoroughly.

You lose almost about 80cm in width and length just because you use ytong, better to take calcium silicate brick in 17cm, you have better sound insulation and the shelves hold.

Thank you for the hints. KS is more difficult to process and also harder to cut, isn't it? Basically, I didn't want to buy expensive 300 EUR saws that I might never need again later ^^ if you say KS is definitely preferable to Ytong and the 300 EUR (then overall hardly matter) should be spent for the number of stones, then I will of course reconsider it gladly.

17.5 should then be enough. 24 might be overkill for the requirements, right? I'm asking because I want to build the thing only once in my life and I don't want to have to add an outer wall later due to lack of stability.

KS has exactly the properties you need...

Static and acoustically better.
Space-saving.

Those few extra minutes of effort should surely be worth the later gain of 3.5 m2 of space?!
And you save expensive adhesive anchors with KS...