How Much Carpet Do I Need?

Carpet doesn't price like tile

Tile costs what your floor area costs. Carpet doesn't.

It comes off a roll of fixed width — usually 12 feet — and you buy a length of it. Everything counterintuitive follows from that.

One extra foot of room nearly doubles what you buy. And a 24-foot room wastes nothing again, because it finally fills the second strip you were already paying for.

The arithmetic

A 16 × 13 room, 12 ft roll, 10% waste allowance:

Strips: 13 ÷ 12 = 1.08 → 2

Linear feet: 2 × 16 × 1.1 = 35.2 ft

Carpet bought: 35.2 × 12 (the roll width, not the room's) = 422.4, shown as 422 sq ft

For a 208 sq ft room. That's 103% total waste.

Turn the room and check again

This is free money and most people never look.

Strips can run either direction, and the two rarely cost the same:

• Across the width: 2 strips × 16 ft = 35.2 linear feet
• Across the length: 2 strips × 13 ft = 28.6 linear feet

6.6 linear feet saved by a decision alone. The calculator shows both — the headline figure and the — or turned 90 degrees row underneath it — for exactly this reason.

But the seam usually outranks the saving

Before you choose on price: seams are permanent, and you'll see them every day.

They're far less visible running along the main light source rather than across it, and along the traffic route rather than perpendicular to it. In a hallway the carpet should run the length, not be seamed across at intervals.

Where the cheap orientation and the good one disagree, the seam generally wins.

Ask the roll width before you measure anything

Twelve feet is most common by a distance — but 15 ft and 13 ft 2 in rolls exist.

That 13-foot room wasting 85% on a 12-foot roll wastes almost nothing on a 15-foot one. If your room is awkward for 12 ft, it's worth asking whether a wider roll is available in the carpet you want. It can genuinely halve the bill.

Pattern repeat is the cost nobody quotes

A patterned carpet needs strips aligned so the pattern matches across the seam — which means cutting each strip to a multiple of the repeat, not to the room.

The calculator doesn't model it, because the repeat length varies by product. Ask the supplier what it costs you in linear feet before ordering. On a large repeat it isn't a small number.

What's not included

Underlay and gripper are separate purchases bought by different measures — underlay by the square yard from its own roll, gripper by the linear foot around the perimeter. Neither follows carpet's roll-width arithmetic, so work them out from the room rather than from the carpet figure.

Also worth thinking about before delivery day: a roll of carpet is long, heavy, and does not bend. Check it can actually get to the room.

Square yards

Carpet is frequently priced per square yard rather than per square foot. Nine square feet to the yard — 422 sq ft is 46.9 sq yd.

Print the measuring sheet — it has a column for both orientations, because comparing them is the single cheapest saving available here.