Question: How do engineers calculate the hypothetical max altitude of a helicopter if the mass, altitude and length/curvature of blades are known?

Answer: 
From the [Source](https://books.google.fr/books?id=FiEapaNgjLcC&pg=PA298&redir_esc=y#v=onepage&q&f=false):

![enter image description here](https://i.stack.imgur.com/1cLJZ.png)

![enter image description here](https://i.stack.imgur.com/d9mrR.png)

![enter image description here](https://i.stack.imgur.com/G4oQf.png)

![enter image description here](https://i.stack.imgur.com/LkPOl.png)
 It shows how to calculate theoretical maximum altitude a Helicopter can achieve
The helicopter reaches its ceiling if all installed power is used for propelling the helicopter forwards: there is no more extra power available to climb.

[![enter image description here](https://i.stack.imgur.com/0zIO7.jpg)](https://i.stack.imgur.com/0zIO7.jpg)

The figure from [this answer](https://aviation.stackexchange.com/a/45643/21091) shows the required power as a function of airspeed: it can be seen that there is an optimal true airspeed where required power has a minimum. It is at this airspeed that the helicopter reaches its OGE ceiling.

So it will be necessary to compute the four types of power at speed and height:

* Propulsive & induced power, depending on rotor blade length, tip speed, blade chord and twist, solidity ratio.
* Profile, depending on blade profile shape.
* Parasitic, depending on fuselage shape, rotor mast shape etc.
* Tail rotor, which is again propulsive & blade power of the tail rotor.