20 square yards to square feet

Twenty square yards is 180 square feet

Why the multiplier is 9

A square yard is a square with sides of 3 feet, so 3 x 3 = 9 square feet sit inside it. Twenty of those squares hold 20 x 9 = 180 square feet. The shape of the patio does not enter the arithmetic, only the count of 3 foot squares.

The same area in the other units is 180 x 144 = 25,920 square inches, and 180 x 0.09290304 = 16.7225472 square meters. NIST Special Publication 811, Appendix B lists one square yard as exactly 9 square feet and exactly 0.836 127 36 square meters, so 20 x 0.83612736 = 16.7225472 with nothing rounded off. The BIPM SI Brochure, 9th edition, gives the other end of the chain: the yard is exactly 0.9144 m, and 0.9144 x 0.9144 = 0.83612736.

Reverse the conversion with one division. 180 / 9 = 20, and 16.7225472 / 0.83612736 = 20. That matters because three different documents describe this one patio: the paver quote in square feet, the sod invoice in square yards, and the imported tile spec in square meters.

One trap lives in the same table. Twenty square feet is 20 / 9 = 2.222 square yards, a small bathroom floor, not a patio. A plan that says 20 feet by 20 feet is 400 square feet, which is 44.44 square yards.

A 180 square foot patio and six other outlines

Area has no fixed outline, and a paver crew prices the outline as much as the area. All of the shapes below hold 180 square feet, so all of them are 20 square yards.

Measure the widest length and the widest width of each rectangle, then multiply. An L shaped patio splits into two rectangles that get measured and added. A curve or a bay gets squared off at its widest point, because the material is cut from straight lengths and the offcut still costs money.

Shape decides the cut list. A 6 by 30 foot walk takes 30 foot runs from 12 foot boards, so every run leaves a 6 foot offcut. The same 180 square feet in a 12 by 15 foot patio nests closer to a whole number of boards. Two jobs with identical area can differ by a bundle of pavers for that reason alone.

If the drawing is dimensioned in feet, keep feet. A plan read as yards instead of feet multiplies the order by 9, which is the single most expensive misreading in this family of pages.

Concrete for a 180 square foot slab at four depths

Concrete is sold by volume, so area becomes a depth first. At 4 inches, 180 x 4 / 12 = 60 cubic feet, and 60 / 27 = 2.222 cubic yards. Those two figures are what a ready mix dispatcher wants, and they describe the same pour.

Bagged mix is quoted by yield. An 80 pound bag of sand mix pours about 0.6 cubic feet, so 60 / 0.6 = 100 bags. A 60 pound bag yields about 0.45 cubic feet and takes 134 bags, since 60 / 0.45 = 133.3 and half a bag is not for sale. Both routes haul roughly 8,000 pounds of material, so a pour this size usually comes off a truck with a chute.

Depth is the free variable once the outline is set. Four inches carries a patio, a shed pad and a spa base. Six inches is where a driveway apron starts. Each extra inch adds 180 / 12 = 15 cubic feet, or 0.556 cubic yards, which is 25 more bags at 0.6 cubic feet.

A plant rounds 2.222 cubic yards up to the next quarter yard and charges a short load fee below a minimum, often 3 yards. Ask for the fee before choosing between 2.25 yards and a pallet of bags, because the difference can land on either side of the truck minimum.

Sod, topsoil and mulch over 180 square feet

Sod is priced by the roll and by the pallet. A common roll covers 10 square feet, so 180 / 10 = 18 rolls, and with 10 percent for edges and trimming the order is 198 / 10 = 19.8, which is 20 rolls. A pallet of 450 square feet covers this lawn 0.4 times, so one pallet leaves more than half in the shade.

Topsoil is ordered by the cubic yard and spread by the inch. One inch over 180 square feet is 180 / 12 = 15 cubic feet, which is 0.556 cubic yards. Two inches doubles it to 30 cubic feet, or 1.111 cubic yards, and that is the depth a thin lawn usually needs before seed will take.

Mulch in 2 cubic foot bags follows the same pattern. At 2 inches deep the bed needs 30 cubic feet, so 30 / 2 = 15 bags. At 3 inches it needs 45 cubic feet, or 23 bags, because 45 / 2 = 22.5 rounds up.

The EPA WaterSense outdoor page puts residential outdoor use at nearly 8 billion gallons a day nationwide, mostly for landscape irrigation, so an area figure off by 10 percent puts the sprinkler schedule off by 10 percent.

Slope is the hidden multiplier in a lawn order. A yard that falls 6 inches across 15 feet has more surface than its plan view, and the extra shows up as a bare strip at the top of the rise. Add 5 percent for a gentle grade and 10 percent for a mound.

Carpet, pad and the 12 foot roll

Carpet is quoted per square yard and woven 12 feet wide, and 20 square yards is the same as 180 square feet from any direction. At $18.50 per square yard the goods cost 20 x 18.50 = $370, or 370 / 180 = $2.06 per square foot.

The roll width decides the seam count, not the area. A 12 by 15 foot room takes one 15 foot drop off a 12 foot roll: 180 / 12 = 15 running feet, which is 5 running yards. Turn the same room the other way and it needs two 12 foot drops cut to 12 feet, so 24 running feet leave a 3 foot wide strip that may never be used again.

Pad, tack strip and labor run on separate lines. Pad at $0.60 per square foot adds $108, the perimeter of a 12 by 15 foot room is 2 x (12 + 15) = 54 feet of tack strip, and installation at $6 per square yard adds $120. The floor total lands near $598 before tax and haul away.

A running yard is not a square yard. On 12 foot goods a running yard covers 12 square feet, so 20 running yards is 240 square feet, a third more carpet than this room needs. The roll width is the factor that a per yard quote leaves out.

Sealer, stain and paint over 180 square feet

Coatings are sold by the gallon and priced by the coat. Take a driveway sealer labelled at 250 square feet per 5 gallon pail, a label figure rather than a standard: one coat over 180 square feet needs 180 / 250 = 0.72 of a pail, so one pail. Two coats need 360 square feet of film, and 360 / 250 = 1.44, which rounds up to two pails.

Paint behaves the same way at a smaller scale. At 350 square feet per gallon, two coats over 180 square feet need 360 / 350 = 1.03 gallons, so one gallon plus one quart if the store sells quarts. A single coat needs 0.51 gallons, which is a half gallon and a wasteful way to buy it.

Fence stain often covers less per gallon than wall paint because rough wood drinks the first coat. At 200 square feet per gallon, 180 square feet takes 0.9 gallons for one coat and 1.8 for two, so two gallons on a rough cedar fence and one on a smooth one.

Bare concrete pulls resin into its pores and can cut coverage by a fifth, which turns a one pail job into a two pail job on the first coat. A moisture test before sealing costs less than a second order and a week of curing in between.

Pavers, tile and bags sold by coverage

A 4 by 8 inch paver covers 32 square inches, so 180 square feet needs 180 x 144 / 32 = 810 pavers. Add 10 percent for cuts and breakage and the order is 891 pavers. Two pallets of 500 cover that with 109 to spare, which is the cheap way to buy the breakage.

Tile ships by the carton. A carton labelled at 24.5 square feet with 10 percent waste takes 198 / 24.5 = 8.08, so nine cartons. Mosaic on 15.5 square foot sheets takes 198 / 15.5 = 12.77, so thirteen sheets, and the difference between those two numbers is why the carton label belongs in the estimate.

Bagged goods are the simplest of the group because the bag already states its volume. Mulch at 2 cubic feet and 2 inches deep takes 15 bags, as the lawn section shows. Play sand at 0.5 cubic feet per bag under a 1 inch sand bed takes 15 / 0.5 = 30 bags, since one inch over 180 square feet is 15 cubic feet.

Round up once, at the end. 810 pavers plus 10 percent is 891, and a supplier who rounds 8.08 cartons down to eight leaves the last course of a patio unfloored. Keep one unopened carton or bundle in the garage for a repair that needs the same dye lot.

Price per square yard, acres and the metric check

Wholesale lists in square yards and invoices in square feet create the classic double markup. At $6.75 per square yard, 20 square yards costs 20 x 6.75 = $135.00, and 6.75 / 9 = $0.75 per square foot. Both lines describe the same material, so a quote that shows only one of them is asking to be compared badly.

Acres appear the moment a site plan does. There are 43,560 square feet in an acre, so 180 / 43,560 = 0.0041 acres, about 1/242 of an acre. A quarter acre lot is 10,890 square feet, which is 1,210 square yards, so this patio is a small fraction of a normal suburban lot.

The metric check is worth doing once. Twenty square meters is 20 x 1.19599 = 23.92 square yards, so a supplier quoting 20 square meters is quoting 19 percent more material than 20 square yards. Getting that direction wrong on imported stone is a four figure mistake.

Sales tax, delivery and old surface removal sit beyond the area rate and do not scale with it. A $150 minimum charge turns a $135 order into a $150 invoice, which is worth knowing before the measure rather than after the truck leaves.