Rug Size Calculator

The 10/21/6-inch border logic tied to furniture arrangement only applies to the living-room branch of the calculation. Dining rooms use a flat clearance so chairs can be pulled out without sliding off, and bedrooms are scaled to about two-thirds of the room's footprint regardless of how furniture sits — so the furniture arrangement selector is only meaningful when Room Type is set to Living Room.

When only the front legs rest on the rug, the rug's edge needs to sit well behind the front legs so the layout doesn't look like the rug is randomly clipping the furniture — that calls for a generous 21-inch margin. When every leg sits on the rug, the rug's edge can run much closer to the wall since nothing needs clearance past it, hence the tighter 10-inch margin.

After computing an ideal length and width, the calculator picks whichever entry in its table of stock rug sizes (3x5 up to 12x18) minimizes the combined difference in both dimensions, then recalculates the border from that final snapped size rather than your original target. That means the reported floor border can end up noticeably tighter or looser than the arrangement-based border you'd expect, especially if your room's proportions fall between two standard sizes.

The recommended length and width are each floored at a minimum (4 ft and 3 ft respectively) before snapping, so in a very small room the suggested standard size could come out close to or larger than the room itself. In that case treat the floor-border output as a warning sign and consider a smaller room type setting or a custom-cut rug instead of a stock size.