How the calculation works
Measure a rectangular room before installing insulation. Count the walls that move each room boundary inward; two opposing walls reduce the same dimension twice. Include insulation, framing, air gaps and finishes in the total thickness. The exact rectangle calculation avoids double-counting corners. It does not assess condensation, energy savings, legal room sizes or property value.
A₀ = L × W A₁ = (L − nL × tA / 100) × (W − nW × tA / 100) ΔA = A₀ − A₁ A₂ = (L − nL × tB / 100) × (W − nW × tB / 100)