Seed Quantity Calculator

Tell it your row length and spacing and it works out how many seeds to sow, buffer included.

📖 How it works & FAQ

Row length

Seed spacing

Over-seed % (germination buffer)

Number of rows

How many seeds do you actually need?

Seed packets never tell you how many seeds to sow for your specific bed. This calculator does the arithmetic for you: it takes the length of your row and the spacing between plants, works out how many plants fit, and then adds an over-seeding buffer so patchy germination doesn't leave you with gaps. The result is a straight, honest count you can take to the store or the seed drawer.

Why the germination buffer matters

Almost no seed lot germinates at 100%. Lettuce and tomatoes might hit 85-95%, while older seed, carrots, or parsley can dip well below that. Sowing exactly one seed per spot means every dud leaves a hole in your row. The over-seed percentage pads your count so you can thin down to the strongest seedlings and still fill the bed. A common starting point is 10-20% for fresh seed and 30%+ for anything old or slow.

How to use it

Enter your row length and pick the unit (feet, inches, meters, or centimeters).
Enter the seed spacing your crop wants, in inches or centimeters.
Set an over-seed % to cover germination losses.
If you're planting several identical rows, bump up the number of rows. Totals update instantly.

These figures are planning estimates, not a guarantee of yield — real germination depends on your seed, soil, and weather.

FAQ

What spacing should I use?: Check the seed packet's in-row spacing. Radishes want about 1 inch, bush beans 3-4 inches, and corn 8-12 inches. Use the final spacing you'll thin to.
How is the seed count calculated?: It divides row length by spacing to get plant slots, multiplies by (1 + your buffer), and rounds up to a whole seed: seeds = ceil(length / spacing × (1 + extra)).
Does this account for row spacing?: No — it counts seeds within a row. The "number of rows" field just multiplies identical rows. Distance between rows doesn't change the seed count.
Should I always over-seed?: For direct sowing, yes. For expensive or pelleted seed you may prefer 0% and simply reseed gaps later. Set the buffer to match your seed quality.