QUESTION: How much space do tomatoes need?
ANSWER: Tomato plants should have at least 24 inches of space between them, and no more than 36 inches between them, for optimal production.
If tomato plants are closer together than 24 inches, the plants will not have enough air circulating around them, which puts them at risk for disease. Especially large vine tomato varieties should be planted with 36 inches of room between plants in a row, with four to five feet of space between rows.
The exception to these guidelines is if you are using the square foot gardening method, in which case you can plant them 12 inches apart. Each tomato plant requires a full 12 inch square.
Learn more about growing tomatoes here.