A packet containing 100 seeds is not a promise of 100 established plants. Some seeds may not germinate, and some seedlings may not survive the next stage. An order for a fixed number of final plants needs to keep those losses separate.
In Seed Quantity Calculator, start with the plant target. Enter expected germination and survival after germination as two percentages. The reserve field adds extra seeds after the expected losses have been allowed for, and the packet fields translate the sowing count into a purchase.
One hundred plants from an imperfect seed lot
For 100 final plants, 85% expected germination and 90% survival, the combined expected success is 76.5%. Before reserve, the calculation needs about 130.719 seeds. A 10% seed reserve brings the estimate to about 143.791, which rounds up to 144 seeds to sow.
If packets contain 50 seeds each, you need three packets. At an example price of PKR 180 per packet, the purchase costs PKR 540. The planned sowing is still 144 seeds, even though the purchased packets contain 150.
At the entered success rates, 144 seeds correspond to 110.16 expected established plants. The fractional result is an average expectation, not a forecast that the garden will produce a fraction of one plant or precisely 110 plants.
Germination and survival describe different stages
Germination is the share of seeds expected to sprout. Survival here is the share of those germinated seedlings expected to establish. Applying a 90% survival figure directly to all purchased seeds while ignoring germination would overstate the expected target.
Use the actual packet information, a relevant seed test or your own records for these entries. Defaults are examples. A seed lot stored differently or sown under different conditions may perform differently, and the tool cannot observe that change.
A very low success percentage can produce a large seed order. Before buying to that number, reconsider whether the assumptions describe a usable seed lot and a realistic plan. Rounding more seeds into packets does not solve poor establishment by itself.
Reserve is not a confidence calculation
Adding 10% spare seeds gives an arithmetic buffer. It does not calculate the probability of achieving the target, and it does not remove the need to check growing conditions and seedling care.
Use Seed Germination Test Calculator if you have counted a seed sample and want its observed percentage. For tray allocation, Seed Tray Planner turns an expected usable cell share into filled cells, whole trays and medium volume. Keep final plants, seeds sown and tray cells as separate counts.