Vegetable Seed Calculator
Examples only • use spacing and germination from your seed packet.
Seed & Sowing Inputs
Seed Plan & Germination
Planning estimateVisual Row & Seedling Layout
Illustrative row • not every planting spot is shown.
Probability model assumes independent seed germination.
Actual results vary with weather, seed viability, soil conditions and transplant survival. Reserved seeds are kept for later use and are excluded from initial germination expectations.
Formula & Worked Example
- Row spots = floor(row length ÷ spacing), same units
- Seeds to sow = spots × seeds per spot
- Occupied spots = spots × [1 − (1 − germination)seeds per spot]
Bed-area spots ≈ floor(area ÷ spacing ÷ row gap). Tray cells = trays × cells per tray. Reserve = ceil(seeds to sow ÷ germination) − seeds to sow, when enabled. Expected thinning = expected seedlings − expected occupied spots.
Frequently Asked Questions
Should I sow more seeds than needed?
Two or more seeds per spot can reduce the chance of an empty spot; keep the strongest seedling and thin the others. The optional reserve is a separate seed stock for later re-sowing, not extra seeds automatically planted at each spot.
What germination rate should I assume?
Use the seed packet or a recent germination test. Crop presets do not set a universal rate. Moisture, soil temperature, seed age and growing conditions affect actual emergence; a laboratory germination percentage is not a harvest survival rate.
Why are expected plants not a whole number?
The result is an average over many possible outcomes, not a literal fraction of a plant. With two seeds per spot at 80% independent germination, a spot has 1 − 0.2² = 96% chance of at least one seedling. Thirty spots therefore average 28.8 occupied spots before later survival losses.
How does tray sowing differ?
The tray model uses number of trays × cells per tray, rather than outdoor spacing. Each occupied cell is thinned to one seedling. Tray columns affect the sampled diagram only. It does not guarantee that every cell will emerge or that all transplants will survive.
More calculation questions
How are seeds calculated?
Initial seeds = planting spots × seeds per spot. With reserve enabled, prepare ceil(initial seeds ÷ germination fraction), keeping the difference as spare seeds. The reserve is a stock-planning convention; it does not guarantee full occupancy.
What inputs are required?
Enter positive row length and spacing, or planted bed area with spacing and row gap, or positive whole tray/cell counts. Seeds per spot must be a positive whole number. Germination may be 0–100%, but a germination-based reserve requires a rate above zero.
How do feet/inches and meters/centimeters work?
The calculator converts both lengths and areas; changing unit systems preserves the same physical dimensions and seed results. For example 10 ft is 3.048 m and 4 in is 10.16 cm. Convert row length and spacing to the same unit before division.
Why might my result differ from another source?
Some tools include both row endpoints, round spot counts up, or count reserve seeds as initially sown. This row model assigns one spacing interval per spot and rounds down. The bed-area model is a density estimate and does not resolve boundary placement, paths or staggered layouts.
Does the diagram predict which seeds will fail?
No. Garden imagery is illustrative. The sowing map samples neutral spots/cells and displays the sowing inputs, not random germination predictions. Expected thinning counts extra emerged seedlings beyond one per occupied spot, assuming independent germination and one retained seedling per spot.
Sources & References
OSU Extension — Vegetable GardeningOregon State University Extension Service ↗
RHS — Vegetable Seed SowingRoyal Horticultural Society ↗Logos identify the linked sources; these organizations do not endorse or validate this calculator.
Vegetable Seed Calculator Calculate how many vegetable seeds to sow for a given row length or area based on plant spacing and germination rate. — free online calculator.