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Seedcalc

Garden Seed Spacing Calculator

Pick your bed size, plants, and planting style. Get seed count, grid layout, and companion-planting suggestions.

Square-foot uses Mel Bartholomew's grid density. Row garden uses traditional between-row spacing. Intensive squeezes 15% more plants in when your soil is rich enough to handle it.

A classic raised bed is 4 feet wide (so you can reach the middle from both sides) and 8 feet long. Enter your real dimensions.

45 species in the database, from arugula to zucchini. Densities from Mel Bartholomew's All New Square Foot Gardening and Johnny's Selected Seeds.

Add companion plants (optional)

When you add a second or third plant, the calculator splits the bed evenly between them. Great for Three Sisters (corn + pole beans + squash) or a classic salad trio (lettuce + carrots + radishes).

What this calculator gets right

Most seed spacing charts hand you a single number per plant and leave you to figure out whether that's for a raised bed, a field row, or an intensive market garden. Those are three different math problems.

This calculator handles all three. Pick your style, enter your bed size, choose your plants, and you get a plant count, a seed estimate, and a packet count so you know what to buy. The species table comes from Mel Bartholomew's All New Square Foot Gardening 3rd edition, cross-checked against Johnny's Selected Seeds technical data and the Old Farmer's Almanac. Read the full guide for how the math works and why some of these numbers differ from what's on the back of your seed packet.

Common questions

What's square-foot gardening?
A method Mel Bartholomew popularized in 1981 that divides a raised bed into 12x12 inch grids. Each square holds 1, 4, 9, or 16 plants depending on spacing needs. Cuts seed use, cuts weeding, and it's the fastest way to learn a new garden.
How many tomato plants fit in a 4x8 raised bed?
32 at Mel's full density, but most home gardeners do 16 to keep airflow up and blight pressure down. Indeterminates like Brandywine or Cherokee Purple sprawl; cut the count by half and trellis aggressively.
When should I plant seeds vs transplants?
Direct-sow root crops, legumes, and anything that germinates fast. Start transplants for tomatoes, peppers, eggplant, and brassicas (broccoli, cabbage, cauliflower). Your local extension office publishes a planting calendar; use it.
What's companion planting?
Putting crops next to each other that help each other grow. Tomatoes and basil. Carrots and onions. The Three Sisters (corn, pole beans, squash). Some pairs deter pests, some fix nitrogen, some provide shade. A few actively fight, like onions and beans.
How deep does a raised bed need to be?
Six inches works for shallow-rooted crops like lettuce and radishes. Twelve inches is the sweet spot for most vegetables. Carrots, parsnips, and tomatoes want 18+ inches. If your bed sits on grass or concrete, don't skimp.

See the full FAQ ->