Why do I need 2× seeds for direct-sow crops?

Two reasons: (1) germination rate is 60-95% even with fresh, properly-stored seeds — some seeds simply won't sprout; (2) you plant 2-3 seeds per spot and thin to the strongest seedling at the 2-leaf stage. Without thinning, the seedlings compete and produce weaker plants. Standard guidance: plant 2× what you need, thin to recommended spacing.

Row planting vs square-foot gardening?

Row: traditional, works for any size garden, allows mechanical cultivation, lower density. Square-foot (grid): higher density, no wasted aisles, requires more soil quality and consistent watering, popularized by Mel Bartholomew (1981). For most home gardens, square-foot wins on yield-per-area; for hobby gardens or where you want kids to walk between rows easily, traditional rows work fine. Calculator handles both; pick based on your goals.

How accurate are the spacing recommendations?

Within typical home-garden tolerances. Recommendations come from agricultural extension services and reputable gardening books, but real spacing depends on: variety (heirloom tomatoes can be 5+ feet wide; bush varieties stay 2-3 feet), climate (more space in humid climates for air flow; less in dry), soil quality (better soil supports denser planting), and gardening style (organic vs intensive). Use the calculator as a starting point; adjust based on local advice.

What about companion planting?

Many crops benefit from companion planting — basil with tomatoes, carrots with onions, beans with corn (Three Sisters), etc. The calculator gives single-crop spacing; for companion planting you'd alternate species within the bed. Permaculture and biodynamic guides cover companion combinations.

Should I direct-sow or use transplants?

Depends on the crop. Root crops (carrots, radishes, beets) MUST direct-sow — they don't transplant well. Leafy greens (lettuce, spinach, arugula) work either way; direct sow is faster, transplants give head-start in cold climates. Tomatoes, peppers, eggplant: almost always start indoors / buy transplants because their growing season is too long to direct-sow in most US climates. Beans, squash, cucumbers: direct sow once soil is warm. Calculator adjusts seed quantities based on your input.

What about row spacing across crops in one bed?

Different crops need different spacing both within a row and between rows. Plan in zones: dedicate one section to tomatoes (their wider spacing), another to lettuce (tight spacing), another to carrots (very tight). Don't try to mix vastly different crops in one row — you'll over-space some and under-space others.

Home & Life · Free tool

Seed Spacing Calculator

Calculate how many plants fit a bed and how many seeds to buy instantly online. Get row and square-foot garden layouts free, no registration needed.

Updated June 2026

Bed length (ft)

Bed width (ft)

Crop

Layout

Plants that fit

32 sq ft bed

Seeds to buy (2x for thinning)

Spacing reference

Tomatoes: 24" between plants, 24" between rows — or 1 plant per square foot (SFG method).

Diagram (approximate)

Bed: 8ft x 4ft  |  8 tomatoes
x x
x x
x x

SFG (square-foot garden) packs more in a small bed but needs rich soil. Traditional rows are easier to weed with a hoe. Seed counts assume 50% germination — buy more if your seed is old.

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What it does

Plan a garden bed: enter dimensions (length × width in feet or meters), pick the crop you’re planting, and the tool returns: number of plants that fit at the recommended spacing for that crop, seeds to buy (typically 2× the plant count to allow for thinning and germination losses), recommended row vs grid layout, and a spacing diagram showing where each plant goes.

Crop spacing recommendations come from established gardening references (e.g. the Farmer’s Almanac, the USDA, classic permaculture / square-foot- gardening references like Mel Bartholomew’s 1981 book). Standard spacings:

Tomatoes: 24-36" apart in rows spaced 36-48" (large plants need air flow to avoid blight).
Lettuce: 6-8" in rows of 12-15" (thinnings can be eaten as microgreens).
Carrots: 1-3" in rows of 6-12" (always over-plant; thin aggressively for proper root development).
Beans (bush): 4-6" in rows of 18-24".
Peppers: 18-24" in rows of 24-30".
Herbs (basil, parsley, cilantro): 8-12" apart, often planted in clumps.

Why 2× seeds: germination rates vary (60-95%), and thinning is part of normal cultivation — you plant more than you need, then thin to the strongest at true-leaf stage. For seedlings (transplants) you buy ready-grown, you don’t need 2×; the calculator adjusts based on your input.

Layout choice (row vs grid) affects total plant count. Row planting is traditional and works for big gardens with mechanical cultivation; grid (square-foot) planting packs more plants per area and works better for small intensive beds. Same crop, different layouts can differ by 20-40% in plant count.

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How to use it

Measure your bed length and width (feet or meters; the tool handles either).
Pick the crop from the dropdown (covers ~60 common vegetables and herbs).
Pick layout: rows (traditional) or grid (intensive / square-foot gardening).
Indicate whether you're sowing seeds or transplanting seedlings — affects whether you need 2× to allow for thinning.
Read the output: number of plants, total seeds to buy, recommended row spacing, expected yield (rough; for crops the data covers).
Use the spacing diagram to mark out planting positions in your bed.

When to use this tool

Planning a vegetable garden in spring before ordering seeds.
Optimizing a small raised bed for maximum production.
Estimating seed quantities to buy without over-spending or running short.
Teaching kids / new gardeners about crop spacing and why it matters.

When not to use it

Highly specialized crops (asparagus crowns, fruit trees, perennial herbs) — those have specialized spacing rules. Use crop-specific guides.
Hydroponic / vertical / specialty growing systems — different math entirely.
Large-scale farming — agricultural spacing accounts for tractor width, irrigation infrastructure, etc.
Permaculture polycultures (multiple species in same bed using companion planting) — those need design experience, not just spacing math.

Common use cases

Educational use — demonstrating the underlying concept
Onboarding a colleague who needs the same calculation/conversion
Verifying a number or output before passing it on
Quick calculation during a typical workday

Frequently asked questions

Why do I need 2× seeds for direct-sow crops?: Two reasons: (1) germination rate is 60-95% even with fresh, properly-stored seeds — some seeds simply won't sprout; (2) you plant 2-3 seeds per spot and thin to the strongest seedling at the 2-leaf stage. Without thinning, the seedlings compete and produce weaker plants. Standard guidance: plant 2× what you need, thin to recommended spacing.
Row planting vs square-foot gardening?: Row: traditional, works for any size garden, allows mechanical cultivation, lower density. Square-foot (grid): higher density, no wasted aisles, requires more soil quality and consistent watering, popularized by Mel Bartholomew (1981). For most home gardens, square-foot wins on yield-per-area; for hobby gardens or where you want kids to walk between rows easily, traditional rows work fine. Calculator handles both; pick based on your goals.
How accurate are the spacing recommendations?: Within typical home-garden tolerances. Recommendations come from agricultural extension services and reputable gardening books, but real spacing depends on: variety (heirloom tomatoes can be 5+ feet wide; bush varieties stay 2-3 feet), climate (more space in humid climates for air flow; less in dry), soil quality (better soil supports denser planting), and gardening style (organic vs intensive). Use the calculator as a starting point; adjust based on local advice.
What about companion planting?: Many crops benefit from companion planting — basil with tomatoes, carrots with onions, beans with corn (Three Sisters), etc. The calculator gives single-crop spacing; for companion planting you'd alternate species within the bed. Permaculture and biodynamic guides cover companion combinations.
Should I direct-sow or use transplants?: Depends on the crop. Root crops (carrots, radishes, beets) MUST direct-sow — they don't transplant well. Leafy greens (lettuce, spinach, arugula) work either way; direct sow is faster, transplants give head-start in cold climates. Tomatoes, peppers, eggplant: almost always start indoors / buy transplants because their growing season is too long to direct-sow in most US climates. Beans, squash, cucumbers: direct sow once soil is warm. Calculator adjusts seed quantities based on your input.
What about row spacing across crops in one bed?: Different crops need different spacing both within a row and between rows. Plan in zones: dedicate one section to tomatoes (their wider spacing), another to lettuce (tight spacing), another to carrots (very tight). Don't try to mix vastly different crops in one row — you'll over-space some and under-space others.

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