Regular pentagon calculator
Tell the tool what you know — the side length, the diagonal, the circumradius, the inradius (apothem) or the area — and it derives every other property of a regular pentagon: area, perimeter, diagonal, circumradius and inradius.
The diagonal of a regular pentagon is side × φ (the golden ratio, ≈ 1.618) and the area is ≈ 1.7205 × side². All calculations stay in your browser.