Understanding your result
The headline is the number of strip pieces to buy, at the strip length you chose, and the line under it is the rows and the linear feet that come from. The tiles give the rows, the total length of strip and the fasteners.
Rows are the number that matters: the dimension across the strips divided by the spacing, plus one for the first row at the wall. With 16 in spacing across a 12 ft ceiling that is 10 rows. Pieces follow from the linear feet with waste, and the table shows how many pieces each row needs so you can see where the butt joints fall; they should be staggered from row to row and land on a joist.
Fasteners depend on what you fasten to. Over joists or studs it is two per crossing plus two at each butt joint; over masonry it is one concrete screw every 16 to 24 in along each strip, as you set it. The board that goes on the strips comes from the ceiling calculator or, for a concrete wall, the basement calculator. For a ceiling where the aim is sound, the channel is a different product: the resilient channel calculator counts it the same way.
How we calculate this
The strip spacing options are the board’s own framing limits, 16 in and 24 in (400 and 600 mm), from the fastener spacing table, which also lists the screw spacing for the drywall that goes on the strips. Strip lengths are stock lengths of furring lumber: 8, 10 and 12 ft, or 2.4 and 3.6 m. Waste covers the offcut at the end of each row and strips too crooked to use.
The calculator assumes rectangular areas. A ceiling with a bump-out or a wall with a window is best run as two rectangles; openings in a masonry wall still need strips around them to carry the board edges, so they are not subtracted.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Strip spacing | 16 in on centre (24 in for 5/8 in board) | Gypsum Association GA-216 framing spacing for gypsum board |
| Strip stock | 1 × 3 (3/4 × 2-1/2 in actual), 8 ft | Common lumber-yard furring; see the standard sizes table |
| Fasteners into framing | Two per crossing, two per butt joint | Standard practice |
| Fasteners into masonry | One concrete screw every 16 in (adjustable) | Concrete screw makers’ guidance for furring; 16 to 24 in is common |
| Waste | 10% | Our figure for row ends and crooked strips |
Assumptions last reviewed October 8, 2026.
The calculator does not size furring for structural use, does not count shims (a bundle per room is the usual buy), and does not design the insulation and moisture control a below-grade wall needs before the strips go on. Furring is not a sound-isolation product; a ceiling that must stop sound uses resilient channel or clips, as the guide to soundproofing ceilings explains. Order of work on a furred ceiling is in the ceilings-first guide.
Two worked examples
A 24 × 13 ft ceiling, strips 24 in apart across 16 in joists, 12 ft strips
- Rows: 156 in ÷ 24 in + 1 = 7
- Linear length: 7 × 24 ft = 168 ft; pieces 168 ÷ 12 × 1.1 = 15.4, rounded up to 16 pieces of 12 ft
- Crossings per row: 288 in ÷ 16 in + 1 = 19; one butt joint per row
- Fasteners: 7 × (19 × 2 + 1 × 2) = 280 screws
At 24 in spacing the ceiling board should be 5/8 in or sag-resistant 1/2 in, and the note says so. Each 24 ft row is two 12 ft strips with the joint on a joist.
A 30 × 8 ft concrete basement wall, concrete screws every 24 in
- Rows: 96 in ÷ 16 in + 1 = 7 horizontal strips
- Linear length: 7 × 30 ft = 210 ft; pieces 210 ÷ 8 × 1.1 = 28.9, rounded up to 29 pieces of 8 ft
- Fasteners: 360 in ÷ 24 in + 1 = 16 per row; 7 × 16 = 112 concrete screws
Horizontal strips on a basement wall carry the board hung vertically, with each sheet’s edges on a strip; some finishers run the strips vertically at 16 in instead so the board can be hung horizontally. Either way the count is the same arithmetic.
Where to find your inputs
Run length. The length of each strip run: the dimension of the ceiling that runs across the joists, or the wall length for horizontal strips on a wall.
Dimension across the strips. The other dimension: the ceiling width along the joists, or the wall height.
Joist or stud spacing. Measure centre to centre; it sets the crossings, and so the fasteners, over framing.
Fastener spacing on masonry. Sixteen inches is a good default; 24 in is common with glue under the strips.
Common mistakes
- Running strips parallel to the joists. They then sit on one joist each and cannot be shimmed flat. Across the joists.
- Spacing the strips from the wrong end. Lay out from the wall where the first sheet starts so every sheet edge lands on a strip.
- Wet or crooked strips. They twist as they dry and the ceiling follows them. Buy straight, dry stock and sort it.
- Skipping the shims. A furred ceiling over sagging joists is only flat if the strips are shimmed to a string line.
- Drywall straight onto bare concrete. Furring creates the space; the moisture plan behind it is what keeps the board dry.
- Treating furring as soundproofing. Strips screwed to joists transmit sound as well as the joists do.
Questions people ask
- How many furring strips do I need for a ceiling?
- Divide the dimension across the strips by the spacing and add one for the rows, then multiply by the length of each run. A 14 × 12 ft ceiling with strips 16 in apart has 10 rows of 14 ft, 140 linear ft, which is 18 pieces of 8 ft before waste and 20 with 10%.
- What spacing for furring strips?
- Sixteen inches on centre for 1/2 in drywall and 24 in on centre for 5/8 in ceiling board, the same spacing the board needs on framing. The spacing must let every sheet's edges and ends land on a strip, so 16 or 24 in on centre, measured from one end.
- What size furring strips for drywall?
- 1 × 3 lumber (3/4 × 2-1/2 in actual) is the common choice for ceilings because it gives room for screws at sheet joints; 1 × 2 is used on walls over masonry where space is tight. Strips must be straight and dry; crooked strips telegraph through the board.
- How do I fasten furring strips to concrete?
- With 3/16 in concrete screws long enough for about 1 in of embedment, or powder-actuated pins, every 16 to 24 in along each strip. Glue under the strip helps. Below grade, the wall needs a moisture plan first; rigid foam board behind the strips is the usual one.
- How many screws for furring strips on joists?
- Two at every crossing where a strip passes under a joist, plus two at every butt joint so both strip ends are held. A 14 ft run across 16 in joists crosses 11 joists, 22 screws per row; 10 rows is about 240 with the joints.
- Should furring strips run across the joists?
- Yes. Strips run perpendicular to the joists so each one is fastened at every crossing and can be shimmed to a flat plane. The drywall then runs perpendicular to the strips, which means parallel to the joists, and every sheet edge lands on a strip.