Scale drawings are created to allow you to plan the space and for others to know and understand your plan.
Contractors that may be working under your instruction need plans to understand where and how you want items placed. Clients will need to visualise the space and be confident that it’s going to work for them before committing to the proposed design and You as the designer, also need to be sure that your proposal is going to work. How embarrassing would it be to order a £15000 bed only to find it doesn’t fit the space!
As mentioned elsewhere on this site there are online tools to help you with the planning, but you will still need to ensure that the measurements you use are correct.
What is scale drawing?