Acreage Calculator

What Is Acreage?

Acreage is how much land there is, expressed in acres. The acre is one of the few units in American measure whose size is a historical accident rather than a round number — 43,560 square feet, a total inherited from the furlong and the chain.

Acreage, Defined

An acre is exactly 43,560 square feet. That is a definition rather than a measurement, and it says nothing about shape: four very different rectangles all return 1.000 acres from this calculator — 220 × 198 ft, 66 × 660 ft, 300 × 145.2 ft, and 43,560 × 1 ft. Only the product of the two sides ever reaches the arithmetic.

Area itself is, in Wolfram MathWorld's phrasing, the amount of material needed to cover a surface completely, and for a rectangle MathWorld gives the one-line formula A = ab, the product of the two side lengths. Acreage is that product carried into acres, so the whole calculation is one multiplication followed by one division.

The word does double duty. A listing that quotes "4.2 acreage" means 4.2 acres; a county record that reports deeded acreage means the acre figure written into the deed. Nothing in the term implies a shape, a use, or whether a single square foot of the parcel can be built on.

Where the 43,560 Comes From

The figure is inherited from plowing. A furlong — the name is a contraction of "furrow long" — is 660 feet, an eighth of the 5,280-foot statute mile. A chain, Gunter's chain, is 66 feet, and 80 of them make that same mile. One chain by one furlong is 43,560 square feet, and that rectangle is the acre.

So the number factors more cleanly than it looks. Ten square chains make an acre: a chain square is 66 × 66 = 4,356 sq ft, and ten of those is 43,560. Enter 66 × 660 ft and the headline reads 1.000 acres, with "43,560 sq ft ÷ 43,560" printed on the line beneath it — the division stated rather than hidden.

Redrawn as a square, an acre is 208.7103 feet on each side, near enough 208 feet 8.5 inches, with a perimeter of 834.84 feet. The familiar 209 × 209 ft shorthand overshoots by 121 square feet: run it and the calculator returns 1.003 acres and 43,681 sq ft.

How Big Is an Acre in Real Terms

The football field is the comparison this calculator uses, and the NFL rulebook makes it exact rather than approximate. Rule 1, Section 1, Article 1 specifies a rectangular field 360 feet in length and 160 feet in width, with goal lines established 10 yards in from each end line.

An acre is therefore 0.756 of a full NFL field, which is where the loose "about three-quarters of a football field" comes from. Laid down the length of a marked field, an acre covers the first 272.25 feet of it — 90.75 yards, stopping just short of the far 19-yard line.

Acres, Hectares and Square Meters

Three of the four units on the panel are fixed by exact definitions, and the fourth is derived from them without any rounding on the way:

• Square foot to square meter: 0.09290304. NIST prints this factor in boldface in its SI guide, the convention that marks a value as exact rather than rounded — the international foot is exactly 0.3048 m, and 0.3048² is that number.
• Acre to square meter: 43,560 × 0.09290304 = 4,046.8564224 m², exact because both inputs are exact.
• Hectare to square meter: 10,000, also boldface in the same NIST table. A hectare is a square 100 m on a side; enter 100 × 100 m and the panel reads "= 1.000 hectares = 10,000 m²".
• Acre to hectare: 4,046.8564224 ÷ 10,000 = 0.40468564224, which is the constant this calculator multiplies by. Inverted, a hectare is 2.4710538 acres — which is why 100 × 100 m leads with 2.471 acres.

One acre entry in the NIST table does not match the figure above, and it is worth knowing about before it turns up on an old plat. NIST lists the acre based on the U.S. survey foot at 4,046.873 m². That foot was defined as 1200/3937 of a meter, a hair longer than the international foot, and NIST deemed it obsolete on January 1, 2023. The gap is 0.0162 m² per acre — four parts per million, about 0.17 square feet — which across a full 640-acre section adds up to 10.36 m². This calculator uses the international foot throughout, and on any parcel a person can walk the difference is far smaller than the tape.

What This Calculator Returns

Three inputs — a unit, a length, a width — and four lines of output. For a 220 × 198 ft parcel, line for line, the panel reads:

Acres and hectares carry three decimals; square feet and square meters are rounded to whole numbers and given thousands separators. Nothing else is computed — no price per acre, no perimeter or fence run, no volume of soil or gravel, no yield or stocking figure, and no check of any kind against a deed or a plat.

Working at room or building scale instead, where the answer wants to be in square feet rather than acres? That job belongs to the Square Footage Calculator.

Both dimension boxes open empty, so the panel sits on its blank state until you press Calculate, and it does not recompute as you type — every change needs the button again. Reset clears the form and the panel together, and Copy puts the headline and the lines beneath it on the clipboard. The arithmetic itself runs in your browser, though the page loads analytics and advertising scripts the way every page on this site does.

How Do You Calculate Acreage?

Multiply the two sides to get square feet, then divide by 43,560. Every other figure on the results panel is a unit conversion hung off that single division.

The Acreage Formula, Written Out

One multiplication, one division, and four fixed factors behind them:

Acres = (Length × Width, in feet) ÷ 43,560

Entered in feet:    square feet = L × W
Entered in meters:  square feet = (L × 3.280839895) × (W × 3.280839895)

From the square-foot total:
  acres    = square feet ÷ 43,560
  hectares = acres × 0.40468564224
  m²       = square feet × 0.09290304
  fields   = acres ÷ 1.32          (shown only from 0.5 acres up)

Fixed values:
  1 acre    = 43,560 sq ft = 4,046.856 m² = 0.404686 hectares
  1 hectare = 10,000 m²    = 2.471 acres

Both dimensions share one unit control, so there is no way to enter a length in feet against a width in meters — convert one of them before typing if your two readings came off different tapes. Metric entries pass through feet on the way, using 3.280839895 where the exact reciprocal of 0.3048 is 3.2808398950131…; that truncation moves an area by roughly eight parts in a trillion, which no display on this page is fine enough to show.

Step by Step

• Decide which two runs are the length and the width. On a rectangular parcel those are the frontage and one side line; on anything else, split it first — the irregular-parcel subsection below covers that.
• Take both readings in the same unit. Feet for a US lot measured off a plat or a wheel, meters if the figures came from a metric survey or an overseas listing.
• Set Measurement Unit to match. It is a two-button segmented control rather than a dropdown, and it opens on Feet, so the highlighted side is the one in force.
• Type the length and the width. Both must be greater than zero: a blank box, a zero, a negative or anything non-numeric returns "Enter the parcel's length and width" in place of an area.
• Press Calculate. Nothing appears on page load, because the two dimension boxes start empty.
• Read the acre headline, then take the hectare or square-meter line if that is the unit your paperwork speaks.

One habit is worth building in before any of this: write feet and inches as a decimal foot, not as a decimal reading of the tape. A frontage of 208 ft 6 in is 208.5, never 208.6 — and against a 200-foot depth that single typo conjures 20 square feet of land that is not there.

Worked Example: a 220 × 198 ft Lot

A one-acre building lot with 220 feet of frontage, worked exactly the way the code works it:

• Unit: Feet. Length: 220. Width: 198.
• Square feet: 220 × 198 = 43,560. Neither dimension is converted, because feet are the working unit.
• Acres: 43,560 ÷ 43,560 = 1, printed to three decimals as 1.000 acres.
• Hectares: 1 × 0.40468564224 = 0.404686, printed as 0.405 hectares.
• Square meters: 43,560 × 0.09290304 = 4,046.856, printed to the nearest whole number as 4,047 m².
• Football fields: 1 ÷ 1.32 = 0.7576, printed to one decimal as 0.8. That line appears at all only because the parcel reaches half an acre.

220 × 198 ft — the headline

1.000 acres

Change the shape without changing the product and the answer does not move. Enter 66 × 660 ft, 300 × 145.2 ft or 43,560 × 1 ft and each returns the same 1.000 acres over the same "43,560 sq ft ÷ 43,560", because the calculator never sees a parcel — only two numbers to multiply.

Measuring in Meters

Metric entries are converted to feet, multiplied there, then converted back, so the hectare and square-meter columns land on the numbers a metric survey would state while the acre column carries the conversion:

100 × 100 m — one hectare

2.471 acres

The last row is a square kilometer: 100 hectares, 247.105 acres. Reading down the two right-hand columns shows why metric land math is easier — every hectare and square-meter entry is a round number, while the acre beside it never is.

Irregular Parcels: Split Into Rectangles

Two numbers multiplied describe a rectangle, so anything with more than four corners, a curved frontage or a creek along one edge has to be reduced to rectangles before it can be entered.

• Sketch the parcel and cut it into rectangles, keeping each boundary either along a rectangle edge or split evenly between what is in and what is out.
• Run each rectangle on its own. An L-shaped parcel made of a 300 × 200 ft body plus a 150 × 100 ft leg returns 1.377 acres and 0.344 acres.
• Add the square footage rather than the acres: 60,000 + 15,000 = 75,000 sq ft, which entered as 250 × 300 ft comes back as 1.722 acres.
• A triangle needs its own formula first, area = ½ × base × height, and the answer goes in against a width of 1. A triangle 400 ft along the road and 300 ft deep is 60,000 sq ft, so 60,000 × 1 ft returns 1.377 acres.

Adding the rounded acre figures instead gives 1.377 + 0.344 = 1.721 acres, one thousandth short of the 1.722 the combined run produces. Both pieces were cut to three decimals before they were added, so the shortfall is the rounding rather than the land. Add square feet, divide once at the end, and the problem cannot arise.

Acreage Chart: Common Parcel Sizes

Every figure in the tables below is this calculator's own output for the dimensions in the first column, not an approximation of one.

The fractions are worth committing to memory, because zoning talks in them: a quarter acre is 10,890 sq ft, an eighth is 5,445, a tenth is 4,356 and a third is 14,520. Note also how the last rows scale — doubling one side doubles the acreage, doubling both quadruples it, which is why 660 × 660 ft is 10 acres and 1,320 × 1,320 ft is 40 rather than 20.

Sections, Quarter Sections and the Famous 40 Acres

Land described under the Public Land Survey System is located by grid rather than by metes and bounds, and that grid is built out of the acre. The Bureau of Land Management's Oregon/Washington land records office states the structure plainly: townships are for the most part 36 square miles or 6 miles square, each township is broken down into 36 sections, and each section is usually 640 acres.

A section is a mile square — 5,280 × 5,280 ft, which this calculator returns as 640.000 acres and 27,878,400 sq ft. Quarter it and you have the 160-acre unit at 2,640 ft square; quarter that and you reach the quarter-quarter section, 1,320 ft square and 40 acres. BLM's own example of a legal description, NE1/4SW1/4, is read from the inside out and lands on exactly that 40-acre parcel.

From the section down, each step is a quarter of the one above it, so the acreage quarters too: 640, 160, 40, 10. The township sits outside that pattern — it holds 36 sections, not four. Note also that miles are not an enterable unit here, which is why the township row is stated as 31,680 feet a side, and that its acre figure prints without a thousands separator — acres and hectares never carry one, only the square-foot and square-meter lines do. If your deed reads in aliquot parts rather than in feet, the acreage is already fixed by the description, and running the dimensions here only confirms it.

How to Read Your Result

Four lines come back, and which of them you need depends entirely on what the figure is for.

Which Line You Need

• The acre headline is the language of US listings, assessor records, zoning minimums and farm leases. Three decimals is finer than most land paperwork asks for, but it costs nothing to carry and it makes near-misses visible.
• The square-foot line drives lot coverage rules, setback math and anything priced by the square foot. It is also the figure to add when you are combining the pieces of an irregular parcel.
• The hectare figure travels. Most of the world lists land in hectares, and it is given to three decimals: 0.405 hectares for an acre, 4.047 for ten acres, 16.187 for forty.
• The square-meter line is the same area for a metric survey or a European plat, rounded to a whole number — 4,047 m² for an acre, 10,000 m² for a hectare.
• The fourth line is a sanity check rather than a measurement. It exists so that a figure like 5.007 acres, which nobody can picture, arrives with "Roughly 3.8 American football fields" attached to it.

When the Football-Field Line Appears

That fourth line switches on at exactly half an acre, and it tests the raw acre value rather than the rounded one on the screen — which produces a pair of results that look contradictory and are not. A 165 × 132 ft parcel is 21,780 sq ft, precisely 0.5 acres, and gets the count: "Roughly 0.4 American football fields (incl. end zones ≈ 1.32 acres each)". A 147.58 ft square is 21,779.86 sq ft, displays as the same 0.500 acres, and gets the acre reminder instead: "An acre is 43,560 sq ft — a square about 209′ × 209′".

Below the threshold that reminder is what the fourth line always says, so a quarter-acre lot and a 40 × 100 ft city lot close on the same sentence. Above it, the count is the acre figure divided by 1.32 and rounded to one decimal: one acre reads 0.8 fields, five acres 3.8, forty acres 30.3, and a full 640-acre section 484.8.

The 1.32 divisor is not a convenience. The rulebook's 360 × 160 ft field is 57,600 square feet, which the calculator itself returns as 1.322 acres, so the divisor is the whole playing surface with both end zones in it. Measure only between the goal lines, 300 × 160 ft, and the same tool gives 1.102 acres.

Deeded Acreage Is Not Usable Acreage

The acreage in a deed governs the sale; what you can actually build on or farm is whatever survives the restrictions on the parcel, which makes it the smaller of the two figures. Setbacks take a strip off every boundary, easements for utilities and access take a corridor through the middle, and wetland, floodway, rock and steep slope take whatever they take.

The arithmetic is worth doing before an offer rather than after. Take that 220 × 198 ft acre and apply a 25 ft setback on all four sides: the buildable envelope is 170 × 148 ft, which this calculator returns as 0.578 acres and 25,160 sq ft. About 42 percent of a deeded acre has gone into rules that leave no trace in the acre figure.

None of which makes the deeded number wrong. It is what the price, the taxes and the legal description all hang on, and it is what this calculator computes. Usable acreage is a separate exercise involving a zoning ordinance, a survey and usually a walk over the ground.

Acreage says nothing about the boundary run, which is what a fence is actually priced by — a one-acre square needs 834.84 feet of line, while a 43,560 × 1 ft strip of the same acre needs 87,122 feet of it. Posts, rails and concrete come out of the Fence Calculator.

Limits: When This Calculator Does Not Apply

The honest boundary of one length times one width, divided by 43,560:

• Any parcel that is not a rectangle, until you have split it yourself. Five-sided lots, curved road frontage, creek boundaries and pie-shaped cul-de-sac lots all need the sketch-and-add treatment first.
• Metes-and-bounds descriptions. If the deed reads in bearings and distances, the area comes out of the traverse, and two numbers cannot stand in for it.
• Any boundary that is in question. A tape, a measuring wheel and this page are all subordinate to a licensed survey and a recorded plat.
• Sloped ground — though not in the way people expect. Land area is a surveying convention: distances are reduced to the horizontal plane, and a plat states the parcel as though it were flat, so a steep five-acre parcel is still five acres even though it carries more surface than that. Enter horizontal distances, not distances paced down a hill.
• Volume of any kind. Gravel, topsoil, mulch and fill all need a depth as well, and no depth is asked for here.
• Prices and yields. No cost per acre, tax rate or crop figure is built in — those are local, they move, and a number baked into a page goes stale.
• Entries under a square foot. A 0.5 × 0.5 ft square returns "0 sq ft ÷ 43,560" and 0.000 acres, because the square-foot line is rounded to whole numbers.

Where the Rounding Shows

Acres and hectares print to three decimals, so the last digit on the acre line is worth about 43.6 square feet — enough to hide a genuine shortfall. A 63.6 × 63.6 m parcel reads 1.000 acres, yet the line under it says "43,540 sq ft ÷ 43,560". The true value is 0.9995 acres, some 20 square feet short of a whole one, and only the second line gives it away.

At the small end the rounding bites the other way. Anything from about 21.8 square feet up reads 0.001 acres, so a 5 × 5 ft square and a 7 × 7 ft square report the same acreage while their square-foot lines, 25 and 49, differ by nearly double. Below that everything reads 0.000 acres, and a single square foot shows "= 0.000 hectares = 0 m²" even though it is 0.0929 m².

Set the rounding against the measurement and it shrinks. One thousandth of an acre is 43.56 square feet; pace a 200-foot frontage two feet long against a 200-foot depth and the parcel reads 40,400 sq ft instead of 40,000 — 400 square feet invented, nine times the value of that last digit. A depth taken down a slope instead of on the horizontal, or a corner assumed square when the parcel is really a parallelogram, moves the answer further again.

Once a depth enters the picture — base for a pad, stone for a drive — the quantity wanted is a volume rather than an area, and that calculation lives in the Gravel Calculator.