Rug Size Calculator — Free Online Tool
The #1 rug mistake is buying too small — a postage-stamp rug makes the whole room look off. This rug size calculator applies the designer's 18-inch border rule to your room dimensions.
What is the Rug Size Calculator?
The standard guidance: leave about 18 inches of bare floor between the rug edge and the wall on all sides. That means subtracting 3 feet total (1.5 per side) from each room dimension. A 12×15 room wants roughly a 9×12 rug — which is why 8×10 and 9×12 are the best-selling sizes in America.
In living rooms, at minimum the front legs of sofas and chairs should sit on the rug; in dining rooms, the rug must extend 24 inches past the table so chairs stay on it when pulled out. This rug size calculator gives the border-rule size — round to the nearest standard rug size when shopping (5×8, 8×10, 9×12).
How to use this calculator
- Measure the room's length and width in feet.
- Enter both and click Calculate Rug Size.
- Round to the nearest standard size (5×8, 8×10, 9×12).
- Check that furniture legs land correctly on the rug.
Formula
Frequently asked questions
Why leave 18 inches of floor around a rug?
It's the designer standard — the border frames the rug and keeps the room feeling grounded. This rug size calculator applies it automatically.
What size rug for a dining room?
The rug should extend at least 24 inches beyond the table on all sides so chairs stay on it when pulled out.
How should a rug sit under a bed?
The rug should extend 18–24 inches beyond each side and the foot of the bed — it doesn't need to go under the headboard.
My rug is too small — any fix?
Layer it over a larger natural-fiber rug (like jute) for an intentional, designer look.