Acre Calculator

Acre Calculator

Updated Aug 19, 2026 By Jehan Wadia

Introduction

This acre calculator tells you how big a piece of land is. You can enter simple measurements, or you can draw the land right on a map. Either way, it gives you the size in acres and five other units.

Pick a shape — rectangle, triangle, circle, trapezoid, or right triangle — then type in the length, width, base, height, or radius. You can use feet, meters, yards, miles, and more. If your land is L-shaped or made of a few pieces, just add more sections. The calculator adds them all up for you.

Prefer the map? Search for an address, then click to drop pins along your property line. Three or more pins close the shape and give you the area. No mouse? Type in latitude and longitude instead.

You get the total in acres, hectares, square feet, square meters, square miles, and square kilometers. You also get the perimeter in feet and meters, which helps if you are planning a fence. A step-by-step section shows the math, and a chart compares your land to things like football fields and parking spaces, so the size is easy to picture.

How to Use Our Acre Calculator

Enter your land size by typing measurements or by drawing your lot on the map. The acre calculator gives you the total area in acres, hectares, square feet, square meters, square miles, and square kilometers, plus the perimeter and step-by-step math.

Measurements tab: Pick this tab to find acres from known lengths and widths.

Land Shape: Choose the shape that matches your land — rectangle or square, triangle, right triangle, circle, or trapezoid. The boxes below change to fit the shape you pick.

Length, Width, Base, Height, or Radius: Type each measurement of your lot. Use numbers greater than zero.

Unit menu: Next to each measurement, pick the unit you measured in — inches, feet, yards, centimeters, meters, kilometers, or miles. You can mix units, and the calculator converts them for you. For standalone unit swaps, try the meters to feet calculator or the area converter calculator.

Add Another Section: Click this to add more shapes for odd lots, like L-shaped or U-shaped land. All sections are added together, and each one shows in the breakdown table. Use the red X to remove a section.

Map tab: Pick this tab to measure real land area on a satellite-style map.

Search box: Type an address, city, or place name and press Search to move the map to your property.

Map clicks: Click each corner of your property to drop boundary pins. After three pins, the shape closes and the acres appear.

Undo Last Pin and Clear All: Use Undo to remove your last pin, or Clear All to start the boundary over.

Latitude and Longitude: If you know exact coordinates, type them in and click Add Pin. This also works if you cannot use a mouse. To check the straight-line gap between two points, the distance calculator can help.

Calculate and Reset: Click Calculate to update your results, or Reset to clear everything and start fresh. Use Copy Results to save the acres and perimeter as text.

What Is an Acre?

An acre is a unit used to measure land. One acre equals 43,560 square feet, or about 4,047 square meters. It is the most common way to measure land size in the United States and the United Kingdom.

The acre started as a farming term. It was about how much land one person with one ox could plow in a single day. Today it is a fixed size, not a guess. An acre has no set shape. A square acre is about 208.7 feet on each side, but an acre can be long and thin or wide and short. Only the total space inside matters.

Acre Size Compared to Things You Know

An acre is a little smaller than an American football field, which covers about 1.32 acres including the end zones. It is close to the size of a city block in many towns. You could fit about 16 tennis courts inside one acre. A common home lot in the suburbs is about a quarter acre.

Common Land Area Conversions

1 acre = 43,560 square feet (see the acres to square feet calculator)
1 acre = 4,046.86 square meters
1 acre = 0.4047 hectares
1 acre = 4,840 square yards (see the square yard calculator)
1 square mile = 640 acres (this is called a "section")
1 hectare = 2.471 acres

Going the other direction? The sq ft to acres calculator handles it in one step.

How Land Area Is Found

To get the acres of a lot, you first find its area in square feet or square meters, then divide. Each shape uses its own formula:

Rectangle or square: length × width — see the area of a rectangle calculator
Triangle: ½ × base × height — see the triangle area calculator
Right triangle: ½ × side A × side B — see the right triangle calculator
Circle: π × radius² — see the circle area calculator
Trapezoid: ½ × (base 1 + base 2) × height — see the trapezoid area calculator

Once you have the area in square feet, divide by 43,560 to get acres. If your area is in square meters, divide by 4,046.86 instead. For a general shape-by-shape tool, use the area calculator or the square footage calculator.

Odd-Shaped Lots

Real land is rarely a neat rectangle. Most lots are L-shaped, U-shaped, or have curved edges. The easy fix is to split the land into simple shapes, find the area of each one, then add them all up. This works for farms, yards, building lots, and pastures. The land area calculator follows the same section-by-section approach.

Why Perimeter Matters

Area tells you how much space is inside. Perimeter tells you how far it is around the edge. You need the perimeter to buy fencing, plan a hedge, mark property lines, or lay a driveway border. Two lots can have the same acreage but very different perimeters, so always check both before buying materials. The perimeter calculator covers single shapes, and the fence calculator turns that boundary length into posts, rails, and panels.

Measuring From a Map

You can also measure land by marking corner points on a satellite map. Each point is set by its latitude and longitude, and the distance between points is measured across the curve of the Earth. This method is fast and works well for large fields, wooded land, and lots you cannot walk across. For legal papers, deeds, or building permits, always use a licensed surveyor.

Where Acres Are Used

Acres show up in real estate listings, farm records, tax bills, zoning rules, and timber sales. Farmers use acres to plan seed, fertilizer, and water — the grass seed calculator, fertilizer calculator, and plant spacing calculator all start from land area. Builders use acreage to check lot coverage rules and to size jobs with the excavation calculator. Homeowners use it for sod, mulch, and lawn care, since most products list coverage per 1,000 square feet or per acre. On the money side, acreage feeds into the property tax calculator, the land loan calculator, and the cap rate calculator when you are valuing a parcel.

Formulas used

Unit conversion of each dimension to meters

L_{m} = L_{unit} \times k_{unit}, \quad k \in \{0.0254,\ 0.3048,\ 0.9144,\ 0.01,\ 1,\ 1000,\ 1609.344\}

Rectangle area and perimeter

A = L \times W, \qquad P = 2(L + W)

Triangle area and perimeter (isosceles assumption)

A = \frac{1}{2} b h, \qquad P = b + 2\sqrt{\left(\frac{b}{2}\right)^2 + h^2}

Right triangle area and perimeter

A = \frac{1}{2} a b, \qquad P = a + b + \sqrt{a^2 + b^2}

Circle area and circumference

A = \pi r^2, \qquad P = 2 \pi r

Trapezoid area and perimeter (isosceles assumption)

A = \frac{b_1 + b_2}{2} h, \qquad P = b_1 + b_2 + 2\sqrt{h^2 + \left(\frac{b_1 - b_2}{2}\right)^2}

Total area and perimeter of all sections

A_{total} = \sum_{i=1}^{n} A_i, \qquad P_{total} = \sum_{i=1}^{n} P_i

Area conversions from square meters

\text{ac} = \frac{A}{4046.8564224},\quad \text{ha} = \frac{A}{10000},\quad \text{ft}^2 = A \times 10.763910416709722,\quad \text{mi}^2 = \frac{A}{2589988.110336}

Geodesic (spherical) polygon area from map pins

A = \left| \frac{R^2}{2} \sum_{i=1}^{n} (\lambda_{i+1} - \lambda_i)\left(2 + \sin\varphi_i + \sin\varphi_{i+1}\right) \right|,\quad R = 6378137\ \text{m}

Great-circle (haversine) edge length and map perimeter

d = 2R\,\arctan\!\left(\frac{\sqrt{a}}{\sqrt{1-a}}\right),\quad a = \sin^2\!\frac{\Delta\varphi}{2} + \cos\varphi_1\cos\varphi_2\sin^2\!\frac{\Delta\lambda}{2},\quad P = \sum_{i=1}^{n} d_i

Frequently asked questions

How accurate is the map measurement?

It is close, but it is not a survey. Your acres depend on how carefully you place each pin. If you click a few feet off at each corner, the total can shift by a few hundred square feet.

Use the map for planning, shopping, and rough estimates. For deeds, permits, or property line disputes, hire a licensed surveyor.

Do I need to click a pin back on my starting point?

No. The calculator closes the shape for you. After your last pin, it draws a line straight back to pin 1 automatically.

If you do add a pin on top of your first one, it just adds a zero-length edge and does not change the area.

Why do my results say dashes or ask me to add more pins?

You need at least 3 pins to make a closed shape. With 1 or 2 pins there is no area to measure.

On the Measurements tab, dashes mean a box is blank, has a letter in it, or has a zero or negative number. Every dimension must be greater than 0.

Does the calculator measure sloped or hilly land?

It gives the flat (horizontal) area, looking straight down from above. That is the same way deeds, plats, and tax records list acreage.

The real walking surface of a steep hill is larger, but that number is not used for legal land size.

Can I subtract a house, pond, or driveway from my land?

There is no subtract button. Do it in two steps:

Measure the whole lot and write down the acres.
Measure just the pond or building the same way.
Subtract the second number from the first.

Can I mix units between sections?

Yes. Each measurement has its own unit menu. You can enter one section in feet and another in meters, and even use feet for length and yards for width.

Everything is converted to meters behind the scenes before the areas are added.

How do I measure a round field, like one with a center pivot?

Pick the Circle shape and enter the radius, which is the distance from the middle to the outer edge.

If you only know the distance all the way across (the diameter), divide it by 2 first.

What is a quarter acre in square feet?

A quarter acre is 10,890 square feet. Here are other common sizes:

1/8 acre = 5,445 sq ft
1/4 acre = 10,890 sq ft
1/2 acre = 21,780 sq ft
1 acre = 43,560 sq ft
5 acres = 217,800 sq ft

My lot is 100 feet by 200 feet. How many acres is that?

That is 20,000 square feet. Divide by 43,560 and you get about 0.459 acres, just under half an acre.

Pick Rectangle, type 100 and 200 in feet, and the calculator shows the same answer plus the perimeter.

Why does the triangle perimeter say it assumes an isosceles shape?

A base and a height are enough to find the area, but not enough to know the two slanted sides. Many different triangles share the same base and height.

So the tool picks the balanced (isosceles) version for the perimeter. If you know your exact side lengths, use the Right Triangle shape or measure each side yourself.

Why is the perimeter of my multi-section lot too big?

When you add sections, the tool adds up each shape's full outline. Where two sections touch, that shared inside edge gets counted even though there is no real fence line there.

For fencing, measure only the true outside edges, or use the map tab and pin the outer corners.

Why is my number a little different from Google Earth or my county map?

Small pin differences add up. Zoom levels, satellite image shift, and where exactly you click each corner all change the result.

A difference of a few percent is normal. A big gap usually means a pin landed in the wrong spot, so undo it and try again.

What does the How Big Is That chart show?

It shows how many familiar things would fit inside your land: football fields, city blocks, tennis courts, basketball courts, and parking spaces.

It is a quick way to picture the size when acres alone do not mean much to you.

Can I use this on a phone or tablet?

Yes. The layout fits small screens, and you can tap the map to drop pins.

If your fingers cover the corners, zoom in first, or type the latitude and longitude and tap Add Pin instead.

Does it work for land outside the United States?

Yes. The map covers the whole world, and you can search any address or city.

Results also show hectares and square kilometers, which are the common land units in most countries.

What is the difference between gross and net acres?

Gross acres is everything inside your property lines. Net acres is what is left after you take out roads, easements, wetlands, or steep parts you cannot build on.

This calculator gives gross acres. Check your plat or local rules to find what counts as usable.

Is my land data saved anywhere?

No. Nothing is stored. If you refresh the page or hit Reset, your pins and measurements are gone.

Use the Copy Results button to save your acres and perimeter as text before you leave.

Can I measure something other than land, like a lake or a roof?

Yes. The math works for any flat shape. Measure a pond, a pasture, a parking lot, or a garden bed the same way.

Just remember a roof with a slope will measure smaller from above than its real surface.

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