Math Formula for figureing out acreage

EddieWalker · Dec 10, 2004

I was thinking about the size of a pasture I'm clearing, and wondered what the formula is for this.

I know an acre is 43,650 square feet.

If it is a perfect square, the 4 sides are a bit over 208.9 feet.

My thinking is if I add up the length of all the sides, or the distance of the perimiter, and devide that by four, then square that number, I come up with a total square footage.

L = Length of a side
P= Perimiter

L1 + L2 + L3 + L4 + L5 + L6 = P

P divided by 4 then squared = Square Footage

Square Footage divided by 43,650 = Acres

Does this work?

My pasture has six sides of various lengths and nothing squares up on it. The perimiter is 1,675 feet. My math comes up with a little over 4 acres.

Thanks,
Eddie

RobS · Dec 10, 2004

Sorry EddieWalker, you don't get out of math class that easy. Take a couple of simple examples:

2X2 square = perimeter of 8 and area of 4. Your math works on this one because it's square.

1X4 rectangle = perimeter of 10 and area of 4. Your formula no longer works.

Your best bet is to break your area up into simple geometric shapes. You can usually do it with rectangles and triangles. Area of rectangles is length times width and area of triangles is 1/2 base times height for a right triangle.

Of course, this is all hard to express in words alone. Any chance you have a picture of your land? Maybe one of those satelite photos?

/forums/images/graemlins/smile.gif

hazmat · Dec 10, 2004

<font color="blue"> Does this work? </font>

Nope.

Your geometry teacher would be dissapointed /forums/images/graemlins/shocked.gif /forums/images/graemlins/tongue.gif

It might give you a rough approximation, but not an exact measurement.

Perimeter is not proportional to area. It is dependant on shape. here's an extreme example to prove it.

Think of a comb that measures 1" x 4" with 100 teeth. If it were a rectangle, the area would be 4 sq in. The rectangle's perimeter would be 10 inches.

The comb has an area less than 4 sq in (subtract the space between the teeth) maybe 2.5 sq in. It's perimeter is 10+ both sides of every tooth (assume .75" lg teeth) = .75*100*2 = 10+150 = 160 inches.

Your best bet is to divide your pasture up into shapes you can measure the area of - rectangles (length * width), and right triangles(one of the three angles= 90 deg) = 1/2 base* height.

Another option is to draw your pasture to scale on graph paper and count the boxes. The area of each box depends on your "scale". Ie each box could be 10ft a side = 100 sq feet.

If available, A copy of you plot of land from the town ought to be drawn to scale...

Good luck.

Jimbrown · Dec 10, 2004

I am sure that will work but this is a heck of a lot easier.
http://www.leaprealtors.com/acreage_calc.htm

Wannafish · Dec 10, 2004

1 Acre = 43,560 (not 650) square feet = 208.71 ft squared.

rdln · Dec 10, 2004

I dont think so, You need to draw the perimeter on a sheet of paper and break it up into the largest squares or rectangles and then make triangles out of the rest but pretend those triangles makes squares or rectangles then cut the L x W figure in half.

hazmat · Dec 10, 2004

Nice link Jim. It clearly illustrates the "break it up into things you can calculate" concept.

BillG_in_TX · Dec 10, 2004

Eddie,

You could just use FL Cracker's method.

Of course, you'll need a Garmin GPSr - but it is nearly Christmas! /forums/images/graemlins/laugh.gif

EddieWalker · Dec 10, 2004

Thanks for the info.

I was hoping to avoid the squares and angles method, and of couse, getting my numbers for an acre wrong really complicated things. hahaha /forums/images/graemlins/confused.gif

I'm plotting things out on my survey and its all just for general knowlege that I'm trying to figure it out.

Eddie