Decimal-Acre Reference / Sheet 0.4

0.4 Acres = 17,424 sq ft

A large suburban lot, roughly twice the median new US home and closing on a half acre. The math is exact: 0.4 multiplied by 43,560 (the international acre constant since the 1959 IYPA) equals 17,424 square feet, or 1,618.74 square metres. Laid out square it is a clean 132 ft on each side, exactly two chains by two chains.

Acres

Square Feet

1,618.7 m²|0.1619 ha|Generous suburban plot

International foot (post-2022 standard)

Pre-loaded at 0.4 acres. Edit either field to recompute. Use survey foot toggle for pre-2022 federal land descriptions only.

Square Feet

17,424

international ft²

Square Metres

1,618.74

m²

Hectares

0.1619

Derivation: 0.4 acres × 43,560 sq ft per acre = 17,424 sq ft, exactly. The constant 43,560 comes from one surveyor's chain (66 ft) multiplied by one furlong (660 ft), formalised internationally by the 1959 International Yard and Pound Agreement. Four tenths of that area is four square chains: laid out square it is two chains by two chains, 132 ft × 132 ft = 17,424 sq ft.

Sheet 02 · Scale References

What 17,424 square feet looks like

A 0.4-acre parcel laid out as a perfect square measures exactly 132 feet on each side, one of the cleanest whole-foot squares in the decimal-acre ladder. Most real 0.4-acre lots are rectangular rather than square: common suburban shapes are 100 ft wide by 174 ft deep, 120 ft by 145 ft, or 90 ft by 194 ft, sized to fit the street grid. The total area is what matters, and 17,424 sq ft sits at the large end of the American single-family suburban range, well above the quarter acre and four fifths of the way to a half-acre plot.

An NBA basketball court

4,700 sq ft

0.4 ac is 3.7× the size

A US doubles tennis court (playing area)

2,808 sq ft

0.4 ac is 6.2× the size

A quarter-acre lot (0.25 acres)

10,890 sq ft

0.4 ac is 1.6× the size

A half-acre lot (0.5 acres)

21,780 sq ft

0.4 ac is 80% of it

A US football field incl. end zones

57,600 sq ft

0.4 ac is 30% of it

The most useful comparison is the half acre: a 0.4-acre lot is exactly 80 percent of a 0.5-acre lot, so it feels like a half-acre plot with a fifth trimmed off. Against a quarter acre, 0.4 acres is exactly 1.6 times as large. Walking the perimeter of a square 0.4-acre lot covers 528 feet, which is exactly eight chains, a little over a minute and a half at a normal walking pace.

Sheet 03 · What Gets Built on 0.4 Acres

The large single-family parcel

Four tenths of an acre is roughly twice the typical American new-home lot. The US Census Bureau Survey of Construction has reported the median lot size for a newly built single-family detached home at about 8,200 to 8,300 sq ft in recent years, which is roughly 0.19 acres. A 0.4-acre lot is more than double that, which places it firmly at the large end of the suburban range: a full detached house with a real yard on every side and room left over for the things a quarter-acre lot cannot fit.

On 17,424 sq ft, a detached house with a footprint of around 2,500 to 3,500 sq ft leaves generous room for a driveway, a front yard, side setbacks, and a large back yard. A two-storey home can deliver 4,000 to 5,000 finished sq ft on that footprint while keeping lot coverage inside the 30 to 40 percent range that most residential zoning districts allow. The extra land over a quarter-acre lot is what makes room for a pool and pool deck, a detached garage or workshop, a sport court, or an accessory dwelling unit where local code permits.

Four tenths of an acre is also close to the threshold where on-site septic becomes practical. Many counties set a minimum lot size for a conventional septic system and drainfield somewhere between a third and a half acre, so 0.4-acre lots are common in the first ring outside sewered subdivisions, where developers platted parcels just large enough to carry their own wastewater treatment. The exact buildable envelope still depends on three local rules that always sit above the raw acreage: the minimum lot size for the zoning district, the maximum lot coverage, and the required front, side, and rear setbacks. A 0.4-acre lot with 35 percent maximum coverage and standard setbacks can support a ground-floor footprint of roughly 6,000 sq ft.

Because 17,424 sq ft is large enough for a big detached home, a real yard, and outbuildings yet small enough to keep maintenance manageable, the 0.4-acre lot is common in lower-density postwar subdivisions, in semi-rural developments, and in higher-end modern communities where lot sizes were set at two or three to the acre rather than five or six.

Sheet 04 · Why 0.4 Acres Shows Up in Records

Where the number comes from

If you searched ".4 acres to square feet" you almost certainly read it on a listing, a tax assessor record, a plat, or a survey. The reason four-tenths of an acre appears so often is that many lower-density subdivisions were platted with lot dimensions that round to roughly 17,400 sq ft, and county assessors report acreage to two decimal places:

132 ft by 132 ft (17,424 sq ft, exactly 0.4 acres): the clean chain-based square, two chains on each side, a dimension that traces straight back to the surveyor's chain used to lay out most of the United States.
100 ft by 174 ft (17,400 sq ft, about 0.4 acres): a wide street frontage with a deeper lot, common where developers wanted a generous house front on a moderate-width road.
120 ft by 145 ft (17,400 sq ft, about 0.4 acres): a near-square wide-frontage lot that rounds to 0.4 acres on a tax record, typical of estate-style subdivisions.

All of these round to 0.4 acres on a public-record search because most US assessor offices report acreage to two decimal places. A 17,200 sq ft lot, a 17,424 sq ft lot, and a 17,600 sq ft lot all display as "0.4 acres" on a county parcel lookup. If precision matters, for example when calculating property tax per square foot or checking a lot-coverage ratio against the zoning maximum, pull the recorded plat and use the survey-grade square footage rather than the rounded acreage.

Watch the two boundaries around 0.4 acres. A true third of an acre is 0.3333 acres, or 14,520 sq ft, about 2,904 sq ft less than a 0.4-acre lot, while a half acre is 21,780 sq ft, about 4,356 sq ft more. On a rounded record a 0.36-acre parcel shows as 0.4 and a 0.44-acre parcel also shows as 0.4, so two lots reported at the same acreage can differ by nearly 3,500 sq ft. When a listing rounds to four tenths, check the recorded square footage before assuming it is closer to a third or a half.

Adjacent Decimal-Acre Pages

Nearby acreages

0.25 ac

10,890 sq ft

0.30 ac

13,068 sq ft

0.50 ac

21,780 sq ft

1.00 ac

43,560 sq ft

Sheet 05 · Common Questions

Frequently asked, 0.4-acre edition

Exactly how many square feet is 0.4 acres?

0.4 acres equals exactly 17,424 square feet, using the international acre standard of 43,560 sq ft per acre defined by the 1959 International Yard and Pound Agreement. The arithmetic is 0.4 multiplied by 43,560. In square metres the equivalent is 1,618.74 sq m, and in hectares it is 0.161874.

What are the dimensions of a 0.4-acre lot?

Area, not shape, defines a 0.4-acre parcel, and 17,424 sq ft can take many rectangular forms. Laid out as a perfect square it measures exactly 132 ft on each side, which is unusually clean because 132 by 132 equals 17,424 to the foot. In surveyor's units that square is exactly two chains by two chains, since a chain is 66 ft. An equivalent clean chain rectangle is one chain by four chains (66 ft by 264 ft). Common platted shapes include roughly 100 ft by 174 ft, 120 ft by 145 ft, or 90 ft by 194 ft, all of which round to 0.4 acres on a county record.

Is 0.4 acres bigger than a third of an acre?

Yes. A true third of an acre is 0.3333 acres, which is 14,520 sq ft, while 0.4 acres is 17,424 sq ft, about 2,904 sq ft larger, roughly 20 percent more land. On a county parcel record acreage is reported to two decimal places, so a 0.34-acre or 0.36-acre lot may display as 0.4 while a 0.33-acre lot rounds to a third. If precision matters, use the recorded square footage rather than the rounded acreage.

Is 0.4 acres a good size to build a house on?

0.4 acres (17,424 sq ft) is a large single-family lot, roughly twice the US median for a newly built detached home, which the US Census Bureau Survey of Construction has reported at about 8,200 to 8,300 sq ft (roughly 0.19 acres) in recent years. It comfortably holds a large house of 3,000 to 4,500 sq ft with a driveway, generous yards on every side, and space for a pool, a detached garage, a workshop, or an accessory dwelling unit where local code permits. At four tenths of an acre a lot is also large enough that on-site septic becomes practical in many jurisdictions, which is one reason 0.4-acre lots are common just outside sewered subdivisions.

How big is 0.4 acres compared to a quarter acre and a half acre?

A quarter acre (0.25 acres) is 10,890 sq ft, so 0.4 acres (17,424 sq ft) is exactly 1.6 times a quarter-acre lot, 60 percent larger. A half acre (0.5 acres) is 21,780 sq ft, so 0.4 acres is exactly 80 percent of a half-acre lot. A 0.4-acre parcel sits four fifths of the way from the quarter-acre suburban standard to the half-acre country plot, closer to the half acre.

How does 0.4 acres compare to a basketball court or a football field?

An NBA regulation basketball court is 4,700 sq ft, so 0.4 acres (17,424 sq ft) is about 3.7 times the size of an NBA court. A US doubles tennis court playing area is 2,808 sq ft, so 0.4 acres is roughly 6.2 tennis courts. A full American football field including both end zones is 57,600 sq ft, so 0.4 acres is about 30 percent of the field, a little under a third.

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