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Microgreens Seed Density Calculator

Find out exactly how much seed to sow for even microgreens tray coverage, by crop, scaled to how many standard trays you're growing.

Seed needed48 g

How to measure your inputs

  • Tray count: how many standard 10"x20" trays you're seeding this round.

Methodology

Direct scaling of published per-tray seeding rates: total seed = grams per standard tray × tray count. Rates sourced consistently from Utah State University Extension's microgreens growing guide, rather than mixing figures from multiple inconsistent sources.

Why microgreens seeding rates vary so much crop to crop

Seed size drives the huge gram-weight differences

Pea shoots need 150g per standard tray while arugula needs just 10g — a 15x difference — mostly because pea seeds are individually far larger and heavier than arugula seeds. Density isn’t about how many plants you want; it’s about achieving even coverage, which takes very different seed weights depending on individual seed size.

Why sourcing one consistent reference matters here

Published microgreens seeding guides vary widely for the same crop — some grower blogs cite figures 2-3x apart for the same species. This calculator deliberately uses one single, consistent university-extension source (Utah State University Extension) rather than mixing numbers from different guides, since inconsistent sourcing would make the figures unreliable to compare across crops.

Scaling beyond a standard tray

These figures are calibrated to a standard 10"x20" ("1020") tray, the near-universal size in commercial and home microgreens growing. If you’re using a different tray size, scale the seed weight proportionally to the tray’s actual area relative to the standard 200 square inches.

Frequently asked questions

Why does pea need so much more seed than arugula?

Pea seeds are dramatically larger and heavier per seed than tiny arugula seeds — achieving the same even tray coverage requires far more total weight even though the seed count per area might be more comparable.

What happens if I use too little seed?

Sparse coverage means lower yield per tray and more open space for weeds, mold, or uneven growth — microgreens are typically grown dense specifically to maximize yield per tray and crowd out competing growth.

What happens if I use too much seed?

Overcrowding increases mold/damping-off risk from poor airflow between densely packed seedlings, and can actually reduce total usable yield if enough of the crop fails to disease.

My crop isn't listed — what should I do?

Look up a seeding rate from a single consistent source (ideally a university extension publication) for your specific crop rather than averaging figures from multiple inconsistent sources, and scale it the same way this calculator does for tray size.