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Area Converter — Square Feet, Square Yards and Acres

One acre is 43,560 square feet, one square yard is 9 square feet and a roofing square is 100 square feet. Enter an area, pick the two units and you get the answer plus the same area in every other unit — useful the moment a site plan, a takeoff and a supplier quote disagree about what they are counting in.

Type a decimal or a fraction — 2.5 and 2 1/2 both work.

Results are estimates for planning purposes. Verify with your supplier, engineer, or a qualified professional before ordering material or performing work.

The numbers worth knowing by heart

UnitIn square feetIn metricWhere it shows up
Square yard90.83612736 m²Carpet, sod, topsoil, concrete flatwork quoted by the yard.
Roofing square1009.290304 m²Shingles and underlayment. Three bundles to a square is the usual pack.
4 × 8 sheet322.9729 m²Plywood, OSB, drywall. Divide the wall area by 32 and round up.
Acre43,5604,046.8564224 m²Land, zoning minimums, site disturbance thresholds.
Hectare107,639.110,000 m²Any drawing produced in metric. A square 100 m on a side.
Section27,878,4002.589988 km²One square mile, 640 acres. The grid square of the Public Land Survey System.

The one that catches people is the square yard: a yard is three feet, so a square yard is nine square feet, not three. Quoting a 1,200 ft² slab as 1,200 yd² overstates it by a factor of nine.

The acre quietly changed size in 2023 — and it did not

An acre is 43,560 square feet. That has not changed and will not. What changed on January 1, 2023 is which foot those square feet are.

The United States carried two nearly identical feet for sixty years. The international foot, exactly 0.3048 m, was adopted in 1959 for everything. The U.S. survey foot, exactly 1200/3937 m, was kept alive as a single exception for geodetic surveying — and never went away. The two differ by two parts per million, which is nothing on a tape measure and several feet on a state plane coordinate in the millions.

NIST and the National Geodetic Survey deprecated the survey foot effective January 1, 2023. Since then the acre, the acre-foot, the rod, the chain and the link are all defined through the international foot. In practice:

  • An acre is 4,046.8564224 m². Older tables — including the 2008 printing of NIST SP 811 itself — give 4,046.873 m², which is the survey-foot acre.
  • The gap is about 4 parts per million — about a fifth of a square foot per acre. It will never matter on a takeoff or a material order.
  • It matters on coordinates. Applying the wrong foot to a state plane northing of two million feet moves you about four feet. That is a survey problem, not an area problem, and it is the reason the deprecation happened.

If you are reading an older legal description or a pre-2023 state plane coordinate, it may still be in survey feet. If you are estimating a job, use the plain foot and stop thinking about it.

Turning an area into an order

An area converter is nearly always the middle step of a material takeoff. The pattern is the same every time: get the plan area into whatever unit the product is sold in, add waste, then round up — you cannot buy 23.4 bundles.

  • Anything with depth is a volume, not an area. Concrete, gravel, topsoil and asphalt are sold by the cubic yard or the ton, and the depth has to enter the arithmetic. Use the concrete slab calculator, the gravel calculator or the asphalt tonnage calculator instead of converting an area.
  • Sloped roofs are bigger than their footprint. A roofing square is 100 ft² of roof surface, not 100 ft² of building. Multiply the footprint by the slope factor before converting.
  • Waste is not optional. Ten percent is the usual starting allowance for cut material, more for a complicated shape or a diagonal layout.

How it's calculated

How the conversion is done
result = area × (m² per from-unit) ÷ (m² per to-unit)
Everything goes to square meters and back, so no chain of rounded factors can accumulate.
The exact factors
1 ft² = 0.09290304 m² · 1 yd² = 9 ft² · 1 roofing square = 100 ft² · 1 acre = 43,560 ft² · 1 mi² = 640 acres · 1 hectare = 10,000 m²
All exact. The foot is defined as exactly 0.3048 m, so the square foot is exactly 0.09290304 m², and every US area unit above is a whole multiple of it.
The acre in metric
1 acre = 43,560 × 0.09290304 = 4,046.8564224 m² = 0.40468564224 hectares
Derived from the international foot, which is the definition in force since the U.S. survey foot was deprecated on January 1, 2023. Older tables print 4,046.873 m² for the acre — that is the survey-foot value, larger by about 4 parts per million.
Coverage, the reason most people are here
area ÷ coverage per unit = units to order
A bundle, a roll, a sheet or a yard of material covers a stated area. Convert the take-off into the unit printed on the product, then round up.

Frequently asked questions

43,560 square feet, exactly. It is not a rounded figure: an acre is defined as 160 square rods, a rod is 16.5 feet, and 160 × 16.5² comes to exactly 43,560 ft². A square acre would measure about 208.71 ft on a side, though acres are rarely square.

Nine. A yard is three feet, so a square yard is three by three. That factor of nine is the single most common area mistake on a jobsite, because carpet, sod, topsoil and concrete flatwork are often quoted per square yard while the drawing is dimensioned in feet.

100 square feet of finished roof area. Roofers price, order and estimate in squares, and asphalt shingles are usually packed three bundles to a square. It is trade usage rather than a published standard, but it is universal in the US roofing trade. A 2,400 ft² roof surface is 24 squares before waste and starter courses.

2.4710538 acres. Going the other way, an acre is 0.40468564 hectares. A hectare is a clean 10,000 m², or a square 100 m on a side, which is why it is the unit of choice on any drawing produced in metric.

One square mile — 640 acres, or 27,878,400 square feet. Sections are the grid squares of the Public Land Survey System that covers most of the United States west of the original colonies, and they are why so many rural parcels come in halves, quarters and sixteenths of 640: a quarter section is 160 acres, a quarter-quarter is 40.

The acre is still exactly 43,560 square feet, and that has not moved. What changed is which foot that means. Until the end of 2022 the acre was defined through the U.S. survey foot; since January 1, 2023 NIST and the National Geodetic Survey have superseded that with the international foot, so the acre in metric is now 4,046.8564224 m² instead of the 4,046.873 m² you will still find in older tables. The difference is about 4 parts per million — a fifth of a square foot per acre, and irrelevant on a takeoff. On a state plane coordinate in the millions of feet, the two-parts-per-million difference between the feet themselves shifts the position by several feet, and that is exactly why the deprecation happened.

Get the plan area into the unit the product is sold in, then round up. Sheet goods come per sheet, so divide by 32 ft² for a 4 × 8 sheet. Shingles come per square of 100 ft². Sod and carpet come per square yard, which is 9 ft². Bulk material comes per cubic yard, which means the depth has to enter the calculation too — that is a volume problem, not an area one.

Because they serve different readers. Building departments, takeoffs and rent are all in square feet; land, zoning minimums and agricultural use are in acres. Divide square feet by 43,560 to move from one to the other. A 10,000 ft² lot is 0.2296 acres, and the common quarter-acre residential lot is 10,890 ft².

Sources & references

Content checked against these sources — last reviewed August 30, 2026.

By — Editorial team of SteelToeTools.com (published by LSEA SAS) Updated v1