Calculators
Tile, slate, shake and flat roof calculators
Pieces per square for tile and slate, bundles of shakes, membrane rolls, rolled roofing and the battens under them.
Tile, slate and shakes are counted in pieces and weighed in hundreds of pounds, not sold in three bundles to the square. The coverage of each piece depends on its size and on the exposure the pitch allows: a slate with a 3-inch headlap covers less than the same slate with a 2-inch headlap, and a cedar shake at a 10-inch exposure covers twice what a shingle at 5 inches does. Flat roofs go the other way, in rolls of membrane 10 feet wide and 50 or 100 feet long, with seams that eat into the width.
Weight matters on every page in this group. Concrete tile at 900 to 1,100 pounds a square is four times the weight of asphalt shingles, and a structure framed for shingles is not automatically able to carry it. The calculators report the weight; whether the roof can hold it is a question for an engineer, and the pages say so.
7 calculators
Concrete & Clay Tile Calculator
Field tiles, pallets, ridge and rake tiles and the dead load for concrete, clay, S-tile and barrel roofs.
Slate Roof Calculator
Slates per square from slate size and headlap, total slates, copper nails and the weight of the roof.
Cedar Shake & Shingle Calculator
Bundles of cedar shakes or shingles at your exposure from the Cedar Shake and Shingle Bureau coverage rules, plus hip and ridge.
Flat Roof Membrane Calculator
Rolls of EPDM, TPO or PVC for a flat roof with turn-ups and seam laps, plus seam tape, adhesive and edge metal.
Rolled Roofing Calculator
Rolls of mineral-surfaced roll roofing for exposed-nail, concealed-nail or double-coverage application, with nails and cement.
Synthetic Slate & Composite Shingle Calculator
Pieces and bundles of synthetic slate or composite shake from piece width and exposure or the data sheet, with starter, ridge and weight.
Roof Battens Calculator
Batten rows, linear feet, pieces and fasteners for a tile or slate roof from the slope length and gauge, with optional counter-battens.
Guides for this topic
Cedar shakes and shingles: exposure, bundles and lifespan
A bundle of cedar does not cover a fixed area: it covers more at a longer exposure. The Bureau's rule makes the count simple once that is clear.
Flat roof membranes: EPDM, TPO and PVC quantities
A flat roof is a membrane, a slope to the drains and as few seams as possible. Here is how to count each one.
How long roofs last, by material
Every roofing material has a typical life, and every roof has a climate, an attic and an installer that move it. Here are the ranges and what to do with them.
Tile and slate: pieces per square, weight and what the structure must carry
Tile and slate last a lifetime and weigh three to five times as much as asphalt. Here is the count, the load and when the framing needs a second look.
Questions people ask
- How many tiles per square?
- Most concrete flat and S-profile tiles cover a square with about 86 to 95 pieces at the manufacturer's standard headlap, so a 25-square roof is around 2,300 tiles before waste. Two-piece clay barrel tile runs 150 to 180 pieces per square because pans and covers are counted separately. The tile calculator uses your product's pieces per square from its data sheet.
- What exposure does slate use?
- Slate exposure is (slate length − headlap) ÷ 2. A standard 18-inch slate with the 3-inch headlap used on pitches of 8/12 and steeper is exposed 7.5 inches; on pitches between 4/12 and 8/12 the headlap grows to 4 inches and the exposure drops to 7 inches. A 10-inch-wide slate at 7.5 inches of exposure covers 0.52 square feet, so a square takes 192 slates.
- How many bundles of cedar shakes per square?
- The Cedar Shake and Shingle Bureau tables give 5 bundles per square for 24-inch shakes at a 10-inch exposure and for 18-inch shakes at 7.5 inches, and 4 bundles per square for 16-inch shingles at 5 inches, 18-inch at 5.5 inches or 24-inch at 7.5 inches. Hips, ridges and starter courses are extra.
- What size is a roll of EPDM?
- EPDM sheet is commonly supplied 10 feet wide in 50- or 100-foot lengths, and also 20 by 100 feet for large roofs, in 45- or 60-mil thickness. A 10 by 100 roll is 1,000 square feet before the 3-inch seam laps and the turn-up at parapets. TPO and PVC come in similar 10-foot rolls with 2- to 3-inch welded laps.
- How many feet of battens for a tile roof?
- Battens run horizontally at the tile's gauge, the spacing between courses. At a 13-inch gauge every square of roof needs 100 ÷ (13 ÷ 12) ≈ 92 linear feet of batten, plus the first course and a few percent for cuts. A 25-square roof is about 2,400 feet, or 300 pieces of 8-foot 1×2.
More calculators on our other sites
Drywalls Calculator
Sheets, screws, joint compound, tape, corner bead, studs, soundproofing and what hanging and finishing drywall costs.
Floorings Calculator
How much tile, wood, vinyl, carpet, underlayment and trim a floor needs, and what it costs.
Paints Calculator
How much paint, primer, stain and wallpaper a job needs, and what it costs.