About this tool
The Rug Size Calculator is a free, in-browser tool that recommends the right area-rug dimensions for a room. Interior designers size a rug around three things: the room's footprint, how it will be used, and where the furniture sits on it. Enter your room length and width, pick the room type and furniture layout, and the tool returns an exact recommended rug size, the nearest standard retail size, and how much bare floor should show around the edges. Everything runs locally in your browser, so nothing you enter is uploaded.
The rules follow common design practice. For an 'all legs on' layout every piece of furniture sits fully on the rug, so the rug is sized to the room minus about a foot of border on each side (room length − 2 ft, room width − 2 ft). For a 'front legs on' living-room layout, and for a 'floating' layout, the rug leaves a wider ~18-inch border (room dimension − 3 ft). Dining rooms are special: the rug must extend at least 24 inches past every edge of the table so chairs stay on the rug when pulled out, so cloth = table length + 48 in by table width + 48 in. The exact result is then snapped down to the nearest standard size (3×5, 4×6, 5×8, 6×9, 8×10, 9×12, 10×14, or 12×15 ft) that still fits the room.
As a worked example, a 15 ft × 12 ft living room with an 'all legs on' layout gives an exact target of 13 × 10 ft, which snaps to a standard 12 × 9 ft rug and leaves roughly 18 in of floor along each side. The general guideline is to keep 8–18 inches of exposed floor between the rug edge and the walls so the room feels framed rather than wall-to-wall carpeted.