The number of tomatoes needed to make one jar of fresh tomato sauce can vary depending on the size of the tomatoes, the desired thickness of the sauce, and the size of the jar. However, I can provide you with a general estimate.
On average, you might need around 8 to 12 medium-sized tomatoes to make one 24-ounce (680 grams) jar of fresh tomato sauce. This assumes that the tomatoes are ripe and have a good amount of flesh and juice. If the tomatoes are smaller or less juicy, you might need a few more to make up the volume.
Keep in mind that making tomato sauce often involves other ingredients like onions, garlic, herbs, and spices, which can also affect the quantity of sauce produced. The best approach is to start with a few tomatoes, make the sauce, and adjust the recipe based on your taste preferences and the desired quantity.