Vegetable Seed Calculator — How Many Seeds to Plant
Enter the number of plants you want, the seed packet germination rate, and any transplant buffer — and get the exact number of seeds to sow and packets to buy.
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Minimum seeds needed to reach your target plant count
- 1
Germination fraction
80 ÷ 100 = 0.8 - 2
Reserve factor
1 + 10 ÷ 100 = 1.1 - 3
Target with buffer
20 × 1.1 = 22 - 4
Seeds to sow (rounded up)
⌈22 ÷ 0.8⌉ = 28Ceiling division ensures you always sow enough for the target even with germination losses.
How does this calculator work?
Divide your target plant count by the germination rate (as a fraction) and round up: Seeds = ⌈Desired ÷ GermRate⌉. Add a 10–15% buffer for transplant losses, then divide by seeds per packet to find how many packets to buy.
Formula
How this is calculated
Seed packets list a germination rate (typically 70–90%) — the percentage of seeds that sprout under ideal conditions. Because some seeds will fail to germinate and others may be lost to damping-off or transplant shock, you need to sow more seeds than your final plant target.
The formula divides the desired plant count (boosted by any extra-buffer percentage you add for transplant losses) by the germination fraction, then rounds up to a whole seed count. Dividing by the seeds-per-packet gives the number of packets to purchase.
Germination rates on packets are measured under controlled lab conditions. Real-world outdoor or unheated-propagator germination is often 5–15 percentage points lower, especially for older seeds. Stored seeds also lose viability each year; if your seeds are more than one season old, reduce the germination rate accordingly before calculating.
Frequently asked questions
Use the rate printed on the seed packet for fresh seeds. For seeds older than one year, reduce by 10–15 percentage points per additional year of storage. If you are unsure, a germination test (placing 10 seeds on damp paper and counting sprouts after the expected days) gives an accurate current rate.
It adds headroom for losses that happen after germination: damping-off disease, frost damage, pest predation, or transplant shock. A 10% buffer on 20 plants adds 2 extra target plants to the calculation, so you sow enough seeds to have 22 survivors rather than exactly 20.
Over-sowing wastes seeds but otherwise does no harm — excess seedlings are simply thinned out once they reach a suitable size. Thinning is preferable to under-sowing and ending up short of plants when the season has already started.
Also known as
TG we-Calculate Editorial Team. (2026). Vegetable Seed Calculator — How Many Seeds to Plant [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/vegetable-seed-calculator
TG we-Calculate Editorial Team. "Vegetable Seed Calculator — How Many Seeds to Plant." TG we-Calculate. 2026. https://we-calculate.com/calculator/vegetable-seed-calculator.
TG we-Calculate Editorial Team, "Vegetable Seed Calculator — How Many Seeds to Plant," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/vegetable-seed-calculator
@misc{wecalculate_vegetable_seed_calculator, title = {Vegetable Seed Calculator — How Many Seeds to Plant}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/vegetable-seed-calculator}}, year = {2026}, note = {TG we-Calculate} }
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