The Land Area Calculator helps you compute the area of land in various shapes and convert between area units.
Supports 6 land shapes (square, rectangle, triangle, trapezoid, circle, and irregular). Converts to 9 units including traditional land measurement units. Includes price estimation and property tax estimates.
Calculator information
📋 How to use this calculator
- Select the land shape: square, rectangle, triangle, trapezoid, circle, or irregular shape.
- Enter side lengths or diameter in feet (for irregular shapes, enter the coordinates of each corner point).
- Choose the desired output unit: square feet (ft²), square meters (m²), acres, hectares, or square yards.
- Optional: enter the land price per square foot to estimate total land value, plus the assessed value to compute property tax.
- Click Calculate to view the area in all selected units along with the estimated price.
- Tip: for irregular parcels, use the shoelace formula with corner coordinates or divide the lot into several triangles.
🧮 Land Area Formulas and Unit Conversions
Rectangle: A = L x W. Triangle: A = ½ x b x h. Trapezoid: A = ½ x (a + b) x h. Circle: A = π x r². Conversions: 1 acre = 43,560 ft² = 4,046.86 m²; 1 hectare = 10,000 m² ≈ 2.471 acres; 1 sq yd = 9 ft².
- L = length, W = width, b = base, h = height, a = the other parallel side
- r = radius, π ≈ 3.14159
- Acres and square feet are standard for US real estate; hectares and square meters appear in survey documents and international transactions
Assessed value, set by the county assessor, is the basis for property tax. Effective property tax rates in the US average roughly 1.1% nationally but vary widely (about 0.3% in HI to 2.2% in NJ) per Tax Foundation data.
💡 Worked example: Calculating a rectangular lot area and estimated property tax
Given:- Shape: rectangle, length 60 ft, width 45 ft
- Assessed value: $20 per ft²
- Homestead exemption: $25,000
- Effective property tax rate: 1.0%
Steps:- Area = 60 x 45 = 2,700 ft², equal to about 0.062 acres or 250.8 m².
- Total assessed value = 2,700 x $20 = $54,000.
- Taxable value = $54,000 - $25,000 = $29,000.
- Annual property tax = 1.0% x $29,000 = $290.
Result: Lot area 2,700 ft² (about 0.062 acres), assessed value $54,000, annual property tax $290.
❓ Frequently asked questions
How do I measure an irregular lot?
For irregular parcels, use the shoelace formula by mapping each corner's coordinates, or split the lot into multiple triangles and trapezoids and sum them. The most accurate method is hiring a licensed land surveyor who produces an ALTA/NSPS survey or a recorded plat. GPS units and drones with photogrammetry software are increasingly common for field measurement.
What is the difference between an acre, a hectare, and a square mile?
An acre equals 43,560 ft² or roughly 4,047 m² - the dominant US land unit, originally the area a yoke of oxen could plow in a day. A hectare is 10,000 m², about 2.471 acres, used in scientific and international contexts. A square mile contains 640 acres or about 2.59 km² and is used for townships and large rural tracts.
What is assessed value and how is it determined?
Assessed value is the dollar value the county assessor places on property for tax purposes. It is typically a percentage of fair market value (ranging from 10% to 100% depending on state law) and is reassessed on a cycle of 1 to 5 years. You can look up your parcel's assessed value on your county assessor's website or property tax bill.
How is US property tax calculated?
Property tax = Mill rate x Taxable value, where Taxable value = Assessed value - Exemptions (homestead, senior, veteran, etc.). Mill rates are set by each taxing jurisdiction (county, city, school district) and combined into a single rate. The national average effective rate is about 1.1% of market value, ranging from 0.3% in Hawaii to over 2% in New Jersey and Illinois.
Can the deed acreage differ from the surveyed acreage?
Yes. Older deeds based on metes and bounds descriptions can be imprecise; modern boundary surveys often reveal small differences. Title companies, lenders, and counties rely on the most recent recorded survey or plat. Always keep your survey and title insurance policy as the strongest legal record of boundaries, not the deed description alone.
📚 Sources & references
Last updated: May 11, 2026