Acreage Calculator

An acreage calculator converts the measurements of a piece of land into acres, the unit used on nearly every U.S. deed, listing and farm record. The rule underneath is one division, square feet ÷ 43,560. The real work is getting the square footage right when the lot is not a neat rectangle, which is why this calculator also handles triangles, trapezoids, circles and irregular four-sided lots and shows every intermediate number.

Three related tools cover the neighboring questions. The Square Footage Calculator is built for rooms, floors and small spaces where an acre is far too large a unit; the Area Calculator handles pure geometry in any unit; and the Land Loan Calculator turns a land price into a monthly payment. Use this page when the question is how many acres a parcel holds or what it costs per acre.

How acreage is calculated for each lot shape

Every method below produces square feet first; the acreage is then that figure divided by 43,560. If you measured in another unit, convert each length to feet before multiplying: 1 yard = 3 ft, 1 meter = 3.28084 ft, 1 rod = 16.5 ft and 1 chain = 66 ft.

Two details trip people up. A triangle's height is the perpendicular distance from the base to the opposite corner, not the length of a side, and that is why Heron's formula is so useful for land: deeds and plats list side lengths, almost never heights. And a four-sided lot cannot be solved from its four sides alone. Sides of 300, 200, 300 and 200 feet can describe a 60,000 sq ft rectangle or a leaning parallelogram with far less area, so the calculator asks for one diagonal, which locks the shape in place.

Worked example: a 5-acre parcel and its price per acre

A rural listing describes a rectangular tract 660 feet deep with 330 feet of road frontage, offered at $87,500. The area is 660 × 330 = 217,800 sq ft, and 217,800 ÷ 43,560 = 5 acres exactly. Dividing the price by the acreage gives $87,500 ÷ 5 = $17,500 per acre, and dividing it by the square footage gives $0.4017 per square foot. Those are the numbers the calculator shows when it first loads.

The same tract shows how the old survey units still mesh with the acre. Sixty-six feet is one chain and 660 feet is ten chains, so the parcel measures 10 chains by 5 chains, or 50 square chains. One acre is 10 square chains, so the answer is again 5 acres, and entering 10 and 5 with the unit set to chains returns the same 217,800 sq ft. The boundary is 2 × (660 + 330) = 1,980 linear feet, and the parcel is 0.781% of a 640-acre section.

Worked example: an irregular four-sided lot

Most real lots are not rectangles. Suppose a plat lists the sides of a wooded lot as AB = 412 ft along the road, BC = 286 ft, CD = 398 ft and DA = 301 ft, plus a diagonal AC = 505 ft from corner A to corner C. The diagonal splits the lot into two triangles, and Heron's formula solves each one from its three sides:

• Triangle ABC: s = (412 + 286 + 505) ÷ 2 = 601.5, so A = √(601.5 × 189.5 × 315.5 × 96.5) = 58,909.56 sq ft
• Triangle ACD: s = (398 + 301 + 505) ÷ 2 = 602, so A = √(602 × 204 × 301 × 97) = 59,880.09 sq ft
• Lot: 58,909.56 + 59,880.09 = 118,789.65 sq ft, and 118,789.65 ÷ 43,560 = 2.727 acres

At an asking price of $129,000 the lot costs $47,304.12 per acre, or $1.09 per square foot. The perimeter, 412 + 286 + 398 + 301 = 1,397 ft, is the length of fence needed to enclose it.

Common lot sizes in acres

The table converts lot dimensions that come up again and again in subdivisions and listings. The last column shows how many lots of that size fit into one acre before any land is set aside for streets; at 8.71 per acre, a 50 × 100 ft lot is a little smaller than an eighth of an acre.

Frontage and depth trade off freely as long as their product stays at 43,560, so 150 × 290.4 ft is the same acre as a square 208.71 ft on a side. Doubling both dimensions quadruples the land: 100 × 200 ft holds four 50 × 100 lots, or 0.4591 acres.

How big is an acre? Side lengths and fence lengths

An acre has a fixed area but no fixed shape. Its traditional form is a strip one furlong (660 ft) long and one chain (66 ft) wide, and 660 × 66 is still exactly 43,560 sq ft. As a square it measures 208.71 ft on each side. The table gives the side of a square for common acreages and its perimeter, which is the shortest four-sided fence that can enclose that much land.

Doubling the acreage multiplies the side by about 1.414, not 2, so a half-acre square is 147.58 ft across while a quarter-acre square is 104.36 ft. The round numbers at the bottom are no coincidence: 40 and 160 acres are the quarter-quarter sections and quarter sections of the federal survey grid, a quarter mile and half a mile on a side.

Rods, chains, sections and townships

Older deeds, metes-and-bounds descriptions and the Public Land Survey System use units that look odd today but convert exactly. NIST defines the rod as 16.5 ft and the chain as 66 ft (4 rods, or 100 links of 7.92 inches), so a square rod is 272.25 sq ft and a square chain is 4,356 sq ft. The acre is 160 square rods or 10 square chains, and a square mile is 640 acres.

The Bureau of Land Management describes most townships as 36 square miles, 6 miles on a side, divided into 36 sections that usually hold 640 acres each. A quarter section is 160 acres and a quarter of a quarter section is 40 acres, which is where a legal description such as "the NE 1/4 of the SW 1/4" comes from. On the ground the grid is only approximately square: north-south lines converge toward the pole, so the BLM notes that sections along the north and west edges of a township are often irregular and split into numbered lots that may hold more or less than 40 acres. The calculator's section share is a size comparison, not a legal description.

Price per acre and what land costs in 2026

Price per acre is the standard yardstick for land because it removes the size difference between parcels. Dividing it by 43,560 gives a price per square foot, which is how land compares with building lots and homes.

For farmland there is an official benchmark. The USDA National Agricultural Statistics Service reported in its Land Values 2026 Summary (July 2026) that U.S. farm real estate, land and buildings together, averaged $4,500 per acre, up 3.4% from 2025. Cropland averaged $6,020 per acre and pasture $2,000 per acre. The spread is wide: regional averages run from $1,710 per acre in the Mountain region to $8,540 in the Corn Belt, and state averages from $735 in New Mexico to $23,600 in Rhode Island. The national figures exclude Alaska and Hawaii.

The per-square-foot column shows the gap between farmland and building lots: the national cropland average is under 14 cents per square foot, while a $100,000 quarter-acre building lot is $400,000 per acre, or $9.18 per square foot. Zoning, road access, utilities and soil decide where a parcel lands in that range, so compare prices per acre only between similar kinds of land.

Three more scenarios

• A triangular corner lot. Two streets meeting at a right angle and a straight back line give sides of 180, 240 and 300 ft. Heron's formula gives s = 360 and A = √(360 × 180 × 120 × 60) = 21,600 sq ft, or 0.4959 acres. Because 180-240-300 is a right triangle, ½ × 180 × 240 gives the same result, a handy check.
• A center-pivot circle. An irrigation pivot with a quarter-mile radius of 1,320 ft waters π × 1,320² = 5,473,911 sq ft, or 125.66 acres, inside a 160-acre quarter section. That is π ÷ 4 = 78.54% of the square, and the four corners stay dry. Priced at the 2026 national cropland average of $6,020 per acre, those 125.66 acres come to $756,495.51.
• A trapezoid-shaped lot. A lot with 200 ft of frontage, a parallel 260 ft rear line and 410 ft of depth covers ½ × (200 + 260) × 410 = 94,300 sq ft, or 2.1648 acres. Measure the depth at a right angle to the frontage, not along a slanted side line.

The acre after the U.S. survey foot was retired

Until the end of 2022 the United States used two feet: the international foot of exactly 0.3048 m and the U.S. survey foot of 1200/3937 m, about two parts per million longer. NIST and NOAA's National Geodetic Survey retired the survey foot, and since January 1, 2023 the international foot is the only foot for new work. NIST now states the acre in international feet: 1 acre = 43,560 sq ft = 4,046.8564224 square meters exactly, against 4,046.872609874 square meters for the old survey-foot acre.

For acreage the change is far too small to notice. The Federal Register notice that announced the decision puts the difference for one acre at 0.000004 acre, about 0.17 sq ft or 25 square inches, and the difference in length at roughly 0.01 ft per mile. A 100-acre farm changes by 0.0004 acre, below the precision of a typical deed. The two feet matter for large coordinates instead: a state plane coordinate of 2,000,000 ft shifts by about 4 ft between the definitions, which is why surveyors label legacy data carefully.

How to use this acreage calculator, and who it is for

1. Pick the shape, or Known area if you already have square feet, square meters, hectares, acres or square miles and only need the conversion.
2. Choose the unit of your measurements: feet, yards, meters, rods or chains.
3. Enter the dimensions. For a four-sided lot, label the corners A to D in order around the boundary and add the diagonal from A to C. For a triangle, choose three sides or base and height.
4. Add a price if you have one: the total price to get the price per acre, or a price per acre to get the total.
5. Read the results: acres in the headline, the conversions below it, the boundary length and section share in the context card, and the full working underneath. The Try buttons load the examples on this page.

Land buyers use it to compare listings quoted in acres, square feet or frontage and depth. Homeowners check a lot against a minimum lot size in a local zoning or septic rule before planning an addition or a barn. Farmers and ranchers turn field dimensions and pivot circles into acres for seed, fertilizer, lease and insurance figures. Agents and appraisers check a stated acreage against the plat and a price per acre against comparable sales, and students use the step-by-step output to check Heron's formula.

Key terms

• Acre: 43,560 square feet, 4,840 square yards, 10 square chains or 160 square rods; 4,046.86 square meters.
• Hectare: 10,000 square meters (100 m × 100 m), equal to 2.4711 acres.
• Gross and net acreage: gross acreage is everything inside the boundary; net acreage subtracts land you cannot use, such as a road right-of-way, an easement or wetland.
• Metes and bounds: a boundary description given as distances (metes) and directions or landmarks (bounds).
• Plat: a recorded subdivision map showing each lot's dimensions.
• Section, quarter section, forty: Public Land Survey System units of 640, 160 and 40 acres.
• Heron's formula: the area of a triangle from its three side lengths alone.

What changes the result, measuring tips and limitations

• Units: a lot measured in meters but entered as feet comes out 10.76 times too small.
• Corner angles: two lots with identical side lengths can differ greatly in area, so measure a diagonal or rely on the area stated on the plat.
• Road frontage: some deeds run to the centerline of the road, so the deeded acreage includes land under the pavement.
• Curves: break a curved line into short straight chords and treat each slice as a triangle; the shorter the chords, the closer the total.
• Cross-checks: compare your figure with the plat, the deed and the county parcel record; a gap of a few percent usually means a mismeasured side or corner angle.

The calculator treats every side as a straight line on a level plane. The four-sided mode assumes the diagonal runs inside the lot, which holds for any lot without an inward-pointing corner; for an arrowhead-shaped lot, use the other diagonal. Lots with five or more corners need to be split into triangles and added over several runs. The tool cannot read a legal description, does not know about easements, rights-of-way or flood zones, and does not replace a boundary survey.

Related calculators

• For rooms, floors and other small areas, use the Square Footage Calculator.
• For the area of any shape in metric or imperial units, use the Area Calculator.
• To compare homes or building lots by price per square foot, use the Price per Square Foot Calculator.
• To turn a land price into a monthly payment, use the Land Loan Calculator.
• To price a fence around the boundary, take the perimeter from this page to the Fence Calculator or the Linear Feet Calculator.
• To estimate the yearly tax on a parcel, use the Property Tax Calculator.

Sources

• National Institute of Standards and Technology (NIST), U.S. Survey Foot: Revised Unit Conversion Factors: acre = 43,560 ft² = 10 ch² = 160 rd² = 4,046.8564224 m²; rod = 16.5 ft; chain = 66 ft; square mile = 640 acres.
• NIST, U.S. Survey Foot: international foot = 0.3048 m exactly; survey foot obsolete from January 1, 2023.
• Federal Register, Deprecation of the United States (U.S.) Survey Foot, 85 FR 62698, October 5, 2020: difference of 0.000004 acre per acre and about 0.01 ft per mile.
• NIST Special Publication 811, Chapter 5, Units Outside the SI: 1 hectare = 10,000 m².
• Bureau of Land Management, The Public Land Survey System, Module 2 Study Guide, and BLM Oregon/Washington, Land Records Help: townships, 640-acre sections, 40-acre quarter-quarters and irregular lots.
• USDA National Agricultural Statistics Service, Land Values 2026 Summary (July 2026): farm real estate, cropland and pasture values per acre.