This is harder than a SWAG, but try it once. For this to work you need a few pieces of information. 1) How many seeds are in a pound and 2) how much to seed (lbs) per acre. What we're gonna do is calculate how many seeds you'll need per square foot. Then, we're going to do a small area and count the seeds we spread. Hold on! Stay with me! You'll need a tarp or a driveway or a paved road that's not so busy.
Lets assume one pound consists of 400-thousand seeds and we are going to spread 12 lbs per acre. So, 12 multiplied by 400-thousand is 4.8 million seeds to spread over 43,560 sq ft. How many seeds is that per square foot? Divided 4,800,000 by 43,560 sq ft equals 110 seeds per square foot which is also equal to about 1 seed per square inch.
You know what a square foot looks like, right? Chalk off a 10 sq ft area on a hard surface (or the kitchen floor). Start walking and cranking and go right thru the middle of your 100 sq foot area. Stop. Go back and look. Does it look like there's one seed per square inch or a hundred in a square foot? Adjust accordingly. It's lots of fun, especially in the kitchen.