Area formulas
Rectangle: S = a × b
Triangle: S = √(p(p − a)(p − b)(p − c)), p = (a + b + c) / 2
Circle: S = π × d² / 4
Trapezoid: S = (a + b) / 2 × h
Room area for renovation
For the floor and ceiling, the area is length × width. For walls, take the room’s perimeter multiplied by the height and subtract windows and doors. The calculator uses a standard window of 1.5 × 1.2 m and a door of 0.9 × 2 m.
Example. A 5 × 4 m room, 2.7 m ceiling, one window and one door. Floor: 20 m². Walls: 2 × (5 + 4) × 2.7 − 1.8 − 1.8 = 45 m². Buy materials with a 10–15% margin for trimming.
Sotkas and hectares
In Russia, land plots are usually measured in sotkas (“hundredths” of a hectare). 1 sotka = 100 m² (a 10 × 10 m plot). 1 hectare = 100 sotkas = 10,000 m². A 40 × 25 m plot is 1,000 m², i.e. 10 sotkas.
For rooms of complex shape, split the plan into rectangles, calculate each one separately and add them up.