Species & Custom Mix Seed Specification Calculator
Build a seed specification for one species or a custom mix. Add species and rates to calculate project weights, live seeds per square foot, composition by seed count and composition by weight.
Return to the starting product
Estimated quantities and composition based on average seed specifications. Actual seed size, seeds per pound, purity and germination vary by seed lot. Use rates appropriate to your site and planting method. Confirm seed-lot specifications, origin and availability before ordering.
1. Project and area
Starts with Pure Live Seed (PLS) weight. Choose bulk weight if your rates are for gross seed weight. Changing intended use or planting method keeps your rates. Area-unit changes preserve your project area. Values stay in this page until you leave; export your work before closing.
2. Species, rates and seed data
Open a species group, check the species you want, then add them together. Enter rates in the compact rows below. Adding or removing species does not rebalance the other rates.
Species list based on Shooting Star's September 8, 2026 list. Availability and origin must be confirmed. Named varieties/forms are separate choices; cover crops include nonnative species. Available average counts are backed by published USDA NRCS or supplier references and are editable. Entries without a verified reference remain blank; use documented seed-lot data for those entries.
For seed density, enter clean seeds per pound from a documented source. With bulk-weight rates, also enter the lot's PLS percentage. A live-seeds-per-square-foot rate needs both values to calculate bulk weight. Origin and lot references are optional. Weight totals can be calculated without seed counts; seed-count composition requires counts for every species.
Your selected species
Optional project notes
3. Mix specification
| Common name | Scientific name | Group | Origin / lot | Clean seeds/lb | Rate lb/acre | Project lb | Project oz | Live seeds/ft² | % by seed count | % by weight |
|---|
Group totals
| Group | Rows | Project lb | Live seeds/ft² | % by seed count | % by weight |
|---|
Percent by seed count = species live seeds/ft² ÷ mix live seeds/ft². Percent by weight = species weight ÷ mix weight on the selected basis. Both use unrounded values; displayed percentages may differ slightly from 100% due to rounding.
Planning specification only; this does not place an order. PLS weight is not gross shipping weight. No waste allowance, package rounding, ecological approval or regulatory certification is applied.
Formulas and data sources
1 acre = 43,560 ft². Project weight = lb/acre × acres. Live seeds/ft² = PLS lb/acre × clean seeds/lb ÷ 43,560. For bulk weight, PLS lb = bulk lb × lot PLS fraction. Lot PLS % = purity % × accepted viability % ÷ 100. Accepted viability may include germination plus eligible dormant or hard seed, according to the test and specification. If total viability already includes those categories, do not add them again.
USDA NRCS calculation reference. Seed-count references were audited on September 26, 2026 against USDA NRCS and published supplier tables. They are planning averages, not seed-lot certificates. Counts supplied per ounce are multiplied by 16 for seeds per pound. Named varieties and seed forms require their own documentation. Every row retains its source in the exported specification. Missing seed data holds back whole-mix seed density and seed-count percentages; weight calculations remain available.
Plan a standard seed mix and supplemental plugs · Calculate plants and flats
Worked example: a one-acre seed specification
This arithmetic example uses two hypothetical components. The rates and seed counts below are sample inputs for learning the calculation; choose actual species and rates for your site and confirm seed-lot data.
| Sample component | PLS lb/acre | Clean seeds/lb | Project PLS lb | Live seeds/ft² | By weight | By seed count |
|---|---|---|---|---|---|---|
| Component A | 2 | 100,000 | 2 | 4.59 | 66.67% | 50% |
| Component B | 1 | 200,000 | 1 | 4.59 | 33.33% | 50% |
| Total | 3 | — | 3 | 9.18 | 100% | 100% |
Project weight = PLS lb/acre × acres. For Component A: 2 × 1 = 2 PLS lb. Live seeds/ft² = PLS lb/acre × clean seeds/lb ÷ 43,560. Both components contribute 200,000 live seeds per acre, so each contributes half of the seed count even though their weights differ.
If each component's lot were 80% PLS, the bulk weights would be 2 ÷ 0.80 = 2.5 lb and 1 ÷ 0.80 = 1.25 lb: 3.75 bulk lb total. Actual lots may have different PLS percentages; calculate each lot separately. No package rounding or allowance is included here.
Calculation reference: USDA NRCS Plant Materials Technical Note 59, pages 2–3. This reference supports the conversion methods; its Colorado planting rates are not recommendations for a Midwest project. Example arithmetic checked September 26, 2026.
Turn your specification into a seed quote
Download your CSV or save a PDF above. Include it with your project location, acreage, desired delivery date and any origin requirements when requesting pricing. Your calculator entries are not automatically sent.
Ecological planning support is available from Nick Fuller, Principal Ecological Officer, whose restoration experience dates to 2004. Natural Communities connects native plant and seed sourcing with site-specific ecological guidance.
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