Plant Spacing Calculator
Enter the bed area and the spacing on the seed packet. The calculator returns the plant count, the density, the spares to buy, and what the same spacing means in a 4x4 raised bed.
Seed packets tell you the spacing and stop there - the math between that and how many plants to actually buy is yours. Crowding is the hidden beginner tax: packed plants compete for light, still air breeds mildew, and the bed that looks fullest in June is often the thinnest at harvest.
How to use
- Bed area first - length times width, honest about the paths.
- Plant and row spacing from the packet, using the final spacing not the thinning distance.
- Read the spares line: 20 percent extra covers the seeds that never take. All three update live.
Frequently asked questions
How many plants fit in a 4x8 raised bed?
At 18 by 24 inch spacing (tomatoes), about 10; at 10 inch spacing (leaf lettuce), about 115. The calculator converts any packet spacing into your bed - and shows the 4x4 equivalent so square-foot-garden plans stay comparable.
What happens if I plant too close together?
Three taxes: competition for light makes every plant leggier and smaller, still air breeds powdery mildew and blight, and roots fight for the same shallow water. The bed looks lush in June and underproduces in August - spacing is the cheapest yield improvement there is.
Does square foot gardening spacing work?
Yes for its intended crops: the 1x1 foot grid is just 12-inch spacing formalized, with 3, 4 or 9 per square for small crops. It runs on the same math as this page - the grid is the spacing, drawn.
Why do I need 20 percent extra seeds or starts?
Germination runs 70-90 percent even on fresh seed, transplants take transplant shock losses, and slugs take their share at night. The 20 percent spare line covers the gap between seeds planted and plants harvested without a second trip to the nursery.