Seed Quantity Calculator

Estimate how many plants you will end up with, and how many seeds to sow, for a row at a chosen final spacing.

How it works

The number of plants a row holds is its length divided by the final spacing between plants. Not every seed germinates and some seedlings are thinned, so the tool adds an allowance (20% by default) to suggest how many seeds to sow:

Plants = (row length m × 100) ÷ spacing cm  ·  Seeds = plants × (1 + extra %)

Sowing a little thicker and thinning to the final spacing is normal for many crops. For crops you raise in modules and transplant, the plant figure is what you need.

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This tool is a planning aid and simply does the maths from the numbers you enter. Order a little extra to allow for settling. Page updated 19 Sep 2026.