Plant as many as you have room for. Between the restaurant and your farmers market, you will need alot. One year, I broadcast spread some basil, probably 4 oz of seeds. I picked what I needed to take to market (so I thought), bagged it in 1/4# packages, loosely packed gal bags. And sold everything I took. Hint, don't seal the bag completely. I could have taken more and sold it. What I did not pick that day was ready for the next market day. I have 3 market days per week.

Plus, the basil smelled really good when the dogs or rabbits ran thru it. At that time, we had a dog that chased the rabbits out of the garden and sometimes thru the basil. I think the dog enjoyed the smell of the basil. At least he didn't roll in it.

I am also in SW Ohio (though likely north of you). I usually do two plantings of basil (genovese, the Classic Italian large leaf type). The first is in mid April in a hoop house and I will do around 50 plants. Than the main planting in Late May will be around 100 plants. This will give me around 10 to 15 pounds a week.

I start them indoors in soil blocks and they are transplanted out at around 6" apart.

I also grow lesser amounts of several other types of basil.

In my market, I've sold 40-50 plants in 1 day, maybe it's just my market. I think my town is basil nuts, it doesn't matter if it's bedding plants, larger plants, stems or just the leaves, it sells. Especially if it's during the tomato season. People start putting up tomatoes and then they want basil for pesto, and in larger quantities.

So each market will be different.

Thanks for all of your responses.

It looks like I'm definitely on the right track with my numbers. Right now I have 170 plants that are 3 to 4 inches tall which I was going to use for plant sales. I also have over 100 which germinated a couple days ago. Those I was going to put out into my garden when the weather permitted.

Basil cannot take temp under 45F-they won't die but the leaves will turn black and young plants may get stunted. I do grow basil in unheated hoop houses with great success but won't start planting them in a hoop house for another 2 to 3 weeks.

they won't be planted out of doors until late May, after all threat of frost/cold weather is over for the summer.

I also have about 100 Italian basil plants about 3-5 inches tall. I will be transplanting them into 4.5 inch pots. Just wondering what I should sell them for and at what height is good. Also should I sell mixed herbs in 1 gallon pails?

no one is saying the TYPE of basil

I also had the same question. Thanks to the previous posters! I'm growing 28 plants in a DWC hydroponic system, and they're about 4" tall now, and working on their fourth leaf sets (after the cotyledon). Based on the above estimates, I will use everything I grow myself. I'm a basil nut!
@QWAERFG - if nobody specifies, then you can usually assume they mean Genovese or sweet basil.(the former is a cultivar of the latter)

I use large leaf italian as my sweet basil. Good seeds, very reasonable prices so that i can charge a reasonable price and people seem to like it.

I usually don't plant more than 5 Genovese basil plants, because they grow to about 4 feet tall and that is plenty. I think I'll start selling the seedlings in the spring.

Sure in Texas they do. LOL!