Seeding Rate Calculator
Convert a target seeding population into pounds of seed per acre, adjusted for germination and purity so you plant the bulk rate you actually need.
How it works
PLS % = germination % × purity % · PLS lbs/acre = target seeds ÷ seeds per lb · Bulk lbs/acre = PLS lbs ÷ PLS %
Seed is sold by weight but planted by population, so you convert your target stand into pounds using the seeds-per-pound figure from the tag. Because not every seed germinates and not every ounce in the bag is seed, you divide by pure live seed (germination × purity) to get the bulk rate you should actually plant. Skipping the PLS adjustment quietly under-seeds the field.
Worked example
For 300,000 seeds/acre of a seed weighing 15,000 seeds/lb, the pure rate is 300,000 ÷ 15,000 = 20 lbs/acre. At 90% germination and 98% purity, PLS is 88.2%, so the bulk rate is 20 ÷ 0.882 ≈ 22.7 lbs/acre.
Sources: USDA NRCS — Pure Live Seed
Frequently asked questions
What is pure live seed (PLS)?
PLS is the fraction of a seed lot that is both viable and actual seed of the species you want: germination percent multiplied by purity percent. A bag at 90% germination and 98% purity is 88.2% PLS, so you plant more bulk pounds to reach your target stand.
Where do I find seeds per pound?
It is printed on the seed tag or in the seed company catalog and varies enormously — from a few thousand per pound for large-seeded legumes to over a million for tiny forage seeds. Always use the figure for your specific lot rather than a generic average.
Should I add seed for poor seedbeds?
Yes. This calculator adjusts for seed quality, not field conditions. On rough, dry or broadcast (non-drilled) seedbeds many agronomists add 10–25% more to offset lower emergence.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.