What Is the Vegetable Seed Calculator?
The Vegetable Seed Calculator tells you how many seeds you need to plant a given garden bed. Instead of guessing — and either running out of seed mid-row or wasting an expensive packet — you enter your row length, the recommended spacing between seeds, and how many rows you plan to sow. The tool returns the total seeds needed, plus a germination-adjusted figure so you can buy or sow a little extra to cover seeds that never sprout.
How to Use It
Enter the row length in centimeters (a 3-meter row is 300 cm). Enter the seed spacing — the distance between each seed along the row, found on most seed packets. Enter the number of rows you intend to plant. Optionally, enter a germination rate (the percentage of seeds expected to sprout); leave it at 100% if you don't want an adjustment.
The Formula Explained
The core calculation is simple: divide the row length by the seed spacing to get the number of seeds that fit in one row, then multiply by the number of rows.
$$\text{Seeds Needed} = \left\lfloor \frac{\text{Row Length}}{\text{Seed Spacing}} \right\rfloor \times \text{Number of Rows}$$
We round seeds-per-row down because you can't plant a fraction of a seed. The germination-adjusted "seeds to sow" figure divides the total by your germination rate and rounds up, so you sow enough to fill the bed even if some seeds fail.
Worked Example
Suppose you have a 300 cm row, seeds spaced 5 cm apart, and 4 rows. Seeds per row = \(300 \div 5 = 60\). Total seeds = \(60 \times 4 = \) 240 seeds. With an 80% germination rate, seeds to sow = \(\left\lceil 240 \div 0.80 \right\rceil = \) 300 seeds.
FAQ
What units should I use? Use the same unit for both row length and seed spacing (this calculator uses centimeters). Consistency is what matters.
Why does it round seeds per row down? A partial seed slot at the end of a row can't hold a whole seed, so rounding down gives a realistic count.
What germination rate should I assume? Most fresh vegetable seed germinates at 75–95%. Check your packet; older seed often sprouts at a lower rate, so sow extra.
