Calculate germination percentage, convert purity and viability to pure live seed (PLS), or estimate seeds and bulk weight per acre, hectare, square foot, or square metre. Choose one focused mode—nothing else is required.
All calculations run in your browser. Inputs are not uploaded, stored, or used for analytics. Use current seed-lot data and a locally appropriate planting target.
How to use the calculator
Choose Germination Test for a simple seed count, Target Stand Seed Rate for a desired established population, or PLS-to-Bulk Conversion for a recommendation already stated as PLS weight.
Enter only current values for this seed lot. Optional crop presets demonstrate common terminology and units but are not planting recommendations.
Read each partial result as it becomes available. Area and seed-weight information are optional until you need a field weight or purchase total.
Add reserve, bag weight, and price only when planning a purchase; calibrate planting equipment to the unrounded rate.
Important: This calculator corrects a target you supply; it does not choose the right seeding rate for a crop or site. Variety, planting date, seedbed, equipment, climate, soil, and local regulations can change the appropriate rate.
Germination, PLS, and seeding-rate formulas
Germination % = normal seedlings ÷ seeds tested × 100
By default, eligible viability is germination alone. If a governing label or recommendation includes hard or dormant seed, the calculator shows that addition explicitly. Example: 85% viability × 98% purity = 83.3% PLS. See Penn State Extension’s PLS examples.
Pure crop seeds to sow = target plants ÷ (germination × field emergence)
Field emergence is applied after the controlled viability result. Seed count does not require purity or seed weight. When weight is known, pure crop-seed weight is divided by purity to estimate ordinary bulk product weight.
Example: 10 lb PLS/ac ÷ 0.80 = 12.5 lb of ordinary bulk seed/ac. Do not apply field emergence again if the recommendation is already stated as a PLS rate. The same conversion is documented by USDA NRCS Plant Materials.
Worked examples you can load
Home test and small garden
Test: 42 normal seedlings ÷ 50 seeds = 84% germination. A 200 ft² garden target of 4 plants/ft² at 90% emergence requires 4 ÷ (0.84 × 0.90) = 5.29 seeds/ft², or about 1,058 seeds total.
Metric wheat with TKW
Inputs: 300 plants/m², 92% germination, 90% emergence, 98% purity, 40 g TKW, 12 ha. Rate: 300 ÷ (0.92 × 0.90) = 362.32 seeds/m². Pure weight is 144.93 kg/ha; bulk weight is 147.89 kg/ha, or 1,774.62 kg total before reserve.
Forage PLS and bags
Inputs: 85% germination × 98% purity = 83.3% PLS. A 10 lb PLS/ac recommendation requires 12.00 lb bulk/ac. Across 10 acres: 120.05 lb exact, 126.05 lb with 5% reserve, three 50 lb bags, and 29.95 lb left after seeding.
Seed germination and seeding rate FAQs
How do I calculate seed germination percentage?
Divide normal, healthy seedlings by seeds tested and multiply by 100. If 42 of 50 seeds produce normal seedlings, germination is 84%.
What is pure live seed (PLS)?
PLS is the share of a bulk lot that is both the intended pure seed and viable. By default, multiply purity by germination. Add eligible hard or dormant seed to the viability basis only when the applicable label or recommendation defines it that way.
How do I adjust a PLS seeding recommendation?
Divide the recommended PLS weight rate by the PLS fraction. A 10 lb PLS/ac recommendation and 80% PLS require 12.5 lb of bulk product/ac.
Why is field emergence separate from germination?
Germination is measured under controlled favorable conditions. Field emergence reflects additional losses from temperature, moisture, crusting, planting depth, disease, vigor, and equipment performance.
Should hard or dormant seed be counted as germinated?
Not in a simple normal-seedling count. Some official labels and crop recommendations incorporate hard or dormant seed into total viability, so follow the seed label and applicable local guidance when those categories are reported.
How many seeds should I test?
A 100-seed home test makes the percentage easy to read, but a larger representative sample or several equal replicates reduces sampling uncertainty. Certified tests follow crop-specific official procedures.
Limitations and common mistakes
Do not confuse a home paper-towel test with an official test conducted under crop-specific temperature, duration, and evaluation rules.
Do not count abnormal seedlings as successful germination merely because a root or shoot appeared.
Do not use PLS-weight mode for a recommendation stated as ordinary bulk pounds per acre; that would overcorrect the rate.
Purity is a weight-based seed-label measure. Count-mode conversion assumes the entered seed weight describes the pure crop seed, then corrects the resulting weight for purity.
The entered reserve is a purchasing allowance; it does not model drill calibration error, seed treatment flow, skips, doubles, headlands, or overlap.
Planning estimate only. Confirm seed quality, target population, treatment requirements, and calibration with the seed label, supplier, equipment manual, agronomist, or local extension service.
Methodology and sources
Prepared by: Starlight Tools editorial team Method reviewed and updated: Review status: No named agronomic reviewer is claimed.
Methodology: the calculator applies the visible equations in sequence, converts every rate through square metres or kilograms, keeps full floating-point precision internally, and rounds only displayed values. Representative hand calculations are checked against the three examples above. Inputs stay in the browser and are not stored.
