How this calculation works
Multiply purity and stated germination as decimal fractions. Divide the required pure live seed mass by that fraction to find bulk mass, then compare total costs for the same target.
PLS fraction = purity × germination; cost per PLS kg = bulk price / PLS fractionA worked example
Lot A at 90% purity and 80% germination is 72% PLS. Ten PLS kg needs 13.889 bulk kg at 100 per kg. Lot B at 95%, 90% and 110 per kg costs about 1,286.55 for the same target, less than lot A’s 1,388.89.
Good to know
PLS accounting only, not field-emergence, certification or crop advice. No separate hard/dormant seed allowance. Compare consistent label conventions; transport, tax and bag rounding are excluded.
Reference: Penn State Extension: calculating pure live seed price (opens in a new tab) ↗
Compare the same useful quantity
A kilogram of bulk seed contains the entered fraction of pure seed, and only the stated germinating share of that fraction counts in this simple PLS model. Multiplying the percentages keeps those stages separate.
A low purchase price can be offset by a low PLS fraction. Comparing the same target PLS mass makes that tradeoff visible without assuming either lot will deliver a particular field stand.
The seed rate from thousand grain weight calculator adds translate an entered plant-density target into kg/ha, kg/acre and field seed mass using thousand-grain weight and sequential establishment factors.
Read label definitions before combining tests
Purity and germination must describe comparable seed lots and testing conventions. If a label or species-specific method treats dormant or hard seed differently, this two-factor calculation may not be the complete specification.
Do not add an extra germination percentage on top of a label value that already includes it. Use current, appropriate test information and retain the distinction between a label test and field establishment.
Separate a continuous requirement from an actual order
The computed bulk kilograms are continuous quantities. Suppliers may sell fixed sacks, impose minimum orders or quote different prices by quantity, so a real purchasing comparison may need those additional details.
Changing the target PLS mass scales both lot totals proportionally under constant entered prices. It does not alter which lot has the lower cost per PLS kilogram.
Use the result with the next measurement
The seed rate from thousand grain weight calculator converts a specified plant-density objective into bulk kilograms. Use the resulting mass basis consistently when comparing purchase prices, without applying purity or germination twice.
PLS accounting only, not field-emergence, certification or crop advice. No separate hard/dormant seed allowance. Compare consistent label conventions; transport, tax and bag rounding are excluded.
A few questions, answered
Is PLS the expected field stand?
No, field establishment depends on additional conditions.
Can cheap bulk seed cost more per PLS kg?
Yes, a smaller PLS fraction can outweigh the lower bulk price.
Are bags rounded up?
No, quantities remain continuous kilograms.