My Designer Friends Swear By the "Two-Thirds Rule" for Living Room Sofas and More

"This easy styling guideline shows up everywhere in well-designed rooms, from perfectly proportioned sofas to thoughtfully organized open shelves. Once you know it, you'll start spotting it in every photo that makes you ask, "Why does that look so good?" What Exactly Is the Two-Thirds Rule? Think of it as the design world's answer to the golden ratio. The idea is that objects or spaces look more balanced when one element takes up about two-thirds of another. It's not about math but about creating visual harmony."

""It grounds my practice through the visual balance it creates for the eye: There is always ease of movement to walk through the room or enjoy the room with company," she says. "When creating a living room, for example, I scale the furniture and arrange it according to the Two-Thirds Rule so that the sofa, coffee table, chairs, and any side tables are proportional on the rug and to the dimensions of the room.""

The Two-Thirds Rule is a simple proportion guideline that creates visual harmony by making one element roughly two-thirds the size of another. Applying the rule to furniture ensures proper scale: sofas should span about two-thirds of a rug, and coffee tables, chairs, and side tables should relate proportionally to both rug and room dimensions. The rule helps anchor seating areas, prevent rugs or furniture from feeling undersized or overpowering, and defines conversation zones. The principle also applies to shelving and groupings, encouraging items of differing sizes that maintain balance and ease of movement for occupants.

Read at Apartment Therapy