Its just length x width.

Measure the front, and the side, and multiply those two numbers. Subtract the house and driveway. For organics, it will get you close enough. If you're applying chems, you might want a more accurate number.

I have an oddly shaped lot, also. I basically cut it into rectangles and triangles. I then calculate the square footage of each piece and add them up. I just calculate the square footage of the grassy area rather than calculate the entire lot and subtract the house.

To calculate the area of a rectangle, multiply two sides that are perpendicular to each other.

To calculate the area of a right triangle, multiply two perpendicular sides and divide by two. If the triangular pieces aren't right triangles, cut the triangle into two right triangles and add the sq footage together.

right, its just l x w if your lot is square or rectangle. i have a pie shaped lot with 5 sides. the front being much shorter than the back because the sides taper.

but i guess i will have to get creative like bp suggests. thanks.

Yes, just divide it into rectangles and triangles. It's the easiest way. You could get fancy with trapezoids and such, but let's keep it simple.

If your like me, it might be harder to find the paperwork than to just step it off, but in my area there is a plot drawing in the closing paperwork. Having the surveyed dimensions is the most accurate.

actually, calculating a trapezoid doesnt sound so bad, lol.

Here is a link that might be useful: http://www.aaamath.com/geo78-area-trapezoid.html

If there is an organic lawn product retailing in America that doesn't give app rates to the nearest 1000 sq. ft. then I've never seen it. Under/over by a few hundred feet isn't going to make one bit of difference. If you're buying seed/sod your going to want to go over regardless. It doesn't need to be so fine.
That's part of the beauty of organics.

Guestimate it.

I have a 35,000 ft^3 lot. My forest is about 10,000 ft^2 (in a triangle [SOH CAH TOA]), the house about 2000 ft^2, driveway about 500 ft^2, beds about 300 ft^2, wood pile about 32 ft^2, etc. All in all I say I have about 20,000 ft^2 of lawn. Get it within 5000 ft^2 and you should be Ok.

If the lawn is on the small side, error to the lesser and add accordingly.

Guesstimation would work just fine, really. Particularly for organics, as long as you aren't seriously low on the guess.

A Pi...er, pie-shaped segment can be calculated by:

Measure one of the straight lines to the point of the pie. Assuming it's actually a pie shape, which one doesn't matter. If it's not and one side is longer than the other, choose the one closest to the average by eyeballing it.

A0 = 3.14 * r * r

(A-sub-zero because this is the first estimate for an entire circle, not the pie itself).

Estimate how much of a circle the pie covers...is it a quarter-pie or a third or a half? Then multiply A0 by that amount, represented by C below

A = A0 * C

That's your base area.

Subtract out the house footprint, plus any gardens and your driveway (S below) and you're good to go.

Afinal = A - S

So, if you live on a quarter pie where the edge from the pie curve to the point is 100 feet...

A0 = 3.14 * 100 * 100 = 31,400 square feet

A = 31,400 * 0.25 (quarter circle from above) = 7,850

Let's say your house and driveway and gardens eat up 2,000 of that...

Afinal = 7,850 - 2000 = 5,850.

5,850 is your total square footage of lawn. Round that to 6,000 to make the math easier (organics not requiring an exact answer...synthetics I'd still use 6 K, though).

If you want to put it all together using the terms above:

Afinal = (3.14 * r2 * C) - S

This ends today's geometry and algebra lesson. :-)

choose the one closest to the average by eyeballing it.

As I think about it, instead of this I'd use the area of an ellipse if it's noticeably squashed on one side (noticeably elliptical, in other words):

In the above, substitute 3.14 * r2 with the following:

Aellipse = 3.14 * A * B

Where A is the longest axis measurement and B is the shortest.

I have a triangle property with sides of 23', 25', 31' what is the square footage?

The area of any triangle can be determined by the formula:
base x height / 2

Here is an awsome calculator that can be used for any lawn. It will calculate any shape and any form of measurent, It will even allow for flower beds!!

Here is a link that might be useful: Fresh Turf Calculator