How to Calculate Acreage

by Lee Grayson

The most accurate, and expensive, way to determine the acreage of a parcel is to hire a surveyor to make the formal determination. The easiest way to locate the parcel acreage is to look at the tax assessment or property title report. Both provide a fairly accurate reporting of the acreage of a parcel. If this information isn't available, or you suspect that the reports have major errors, determining the acreage using an online calculator is fast and easy. People without access to the Internet, need to do some "old school"-style calculations using paper and pencil to figure out the total acreage of a parcel.

Online Calculator Approach for Regular Parcels

1. Locate an online acreage calculator on the Internet by using the search terms "acreage calculator."

2. Type the width in feet of the parcel in the blank space for "width."

3. Insert the length in feet of the parcel from your property tax or title reports in the blank space for "length."

4. Click on the webpage icon labeled "submit," "calculate" or "find acreage" to return the amount of total acreage.

Online Calculator Approach for Irregular Parcels

1. Locate an online acreage calculator allowing the use of a diagonal distance or directional degree on the form by conducting an Internet search using the search terms "acreage calculator."

2. Locate at least one of the diagonal distances or directional degrees for one angle from the information listed on the title report or county property tax records describing the parcel. The county property description typically includes a narrative with a starting direction for the first parcel measurement, then the number of degrees and a statement of the next measurement. Use any of the parcel degrees with the online calculator.

3. Insert the distance measurements for the sides of the property parcel into the online form using meters, feet or yards.

4. Enter one of the property degree angles or a diagonal distance on the online form.

5. Click on the page icon labeled "recalculate," "calculate" or "area total" to receive the total acreage for the parcel.

Old-School Approach

1. Locate the width and length of the parcel from the property tax or title report.

2. Multiply the parcel's width in feet by the length in feet. This calculation provides the net square footage.

3. Divide the total net square footage by 43,560 -- the square footage of an acre -- to provide the total acreage of the parcel.

Graph Paper Approach

1. Locate a copy of the parcel made by an engineer or surveyor. County or city assessor offices and title reports typically provide maps for use in this graph paper approach to calculating acreage.

2. Place the graph paper over the map and trace the outside boundaries of the parcel.

3. Locate the scale of the map by looking at the scale listed. The scale typically uses 1 inch to represent 100 feet, but the map may use another representation.

4. Determine the scale of each grid for your graph paper. Measure the length of any grid on the paper and multiply this figure by the scale used on the assessor or title report map. This squared sum equals the area represented by each of the grids on the graph paper. The squared figure represents the sides of the grid box. The formula to determine each grid's scaled length uses this calculation: Measured length of the grid square x scale of map - scaled length of square.

5. Fill in the grid squares for the parcel. Fill in the grid square completely for areas of the property covering the entire square. The grid squares in the center of the property typically have full grid marks. The grid squares around the parcel's edges require partial fill marks. If the property edges cover one-quarter of the grid square, mark the square with "1/4." Mark the grid squares covered approximately one-half with a "1/2" label. Label grid squares filled by three-quarters of the property with "3/4."

6. Complete a chart for the grid squares. Label the top row "full," "3/4," "1/2" and "1/4," and count the number of squares from your graph paper matching the labels. A paper with 30 complete squares, for example, shows this number under the column labeled "full."

7. Calculate the acreage of the parcel using your chart. Multiply the number under the chart labeled full by 1. Multiply the number squares under the chart labeled "3/4" by 0.75 and the number on your chart under "1/2" by 0.50. Multiply the number on the chart listed "1/4" by 0.25. These figures represent the amount of land in the grid squares.

8. Add the numbers for each of the column totals from Step 7. This figure represents the total grids filled on the graph paper.

9. Convert the grid information from Step 8 into acreage. Multiply the number of filled grid squares calculated in Step 8 by the area of the grid square from Step 4 to find the total area of the parcel. The formula ((number of squares) x (area of a grid square) = total area) provides this information.


  • Several states, including Michigan, offer information for land parcels online. Most link this information from the city or county assessor's webpage.


  • Property parcels with uneven boundaries require some rounding up or down of the measurements to create more even boundary lines for use in the calculations. This smoothing technique, however, creates minor errors in calculating the exact acreage amount.

Items you will need

  • Parcel dimensions
  • Internet access
  • Calculator
  • Graph paper

About the Author

Lee Grayson has worked as a freelance writer since 2000. Her articles have appeared in publications for Oxford and Harvard University presses and research publishers, including Facts On File and ABC-CLIO. Grayson holds certificates from the University of California campuses at Irvine and San Diego.

Photo Credits

  • Hemera Technologies/ Images