Grass Seed Calculator
Grass seed calculator works out Pure live seed and Bulk seeding rate required from Calculation, Target pure-live-seed rate and Purity. The default figures on this page give bulk seeding rate required of 13.586957; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
3 steps
- Pure live seed = purity x germination / 100 = 92 x 80 / 100 = 73.6%
- Bulk rate = target x 100 / PLS = 10 x 100 / 73.6 = 13.586957
- That is 35.87% more seed than the target rate, to allow for impurity and non-viable seed.
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
3 sources
What the grass seed calculator calculates
Adjusts a target seeding rate for seed-lot purity and germination, and estimates stand population from a sampled row count.
How to use this grass seed calculator
Enter Calculation, Target pure-live-seed rate, Purity and Germination. Pure live seed updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Pure live seed, Bulk seeding rate required and Increase over the target rate.
The method follows Penn State Extension, Calculating the Price of Pure Live Seed, University of Minnesota Extension, seeding rate for small grains and Stand counts scale a sampled area to the whole field by the exact acre and hectare constants..
Research pls-f01: 92% purity, 80% germination example
With Calculation: pls, Target pure-live-seed rate: 10, Purity: 92, Germination: 80, the calculator returns Pure live seed: 73.6, Bulk seeding rate required: 13.5869565. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Pure live seed, Bulk seeding rate required and Increase over the target rate. The inputs you can vary are Calculation, Target pure-live-seed rate, Purity, Germination, Plants counted and Length of row sampled.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do you calculate how much grass seed you need?
Adjusts a target seeding rate for seed-lot purity and germination, and estimates stand population from a sampled row count. Open “How this is worked out” beside the result to see each step for your own figures.
How much will a 50 lb bag of grass seed cover?
On the figures this page opens with — target pure-live-seed rate 10, purity 92% and germination 80% — the bulk seeding rate required is 13.586957. No single number fits everyone: change any figure above and the answer updates as you type, with each step of the arithmetic beside it.
How many square feet will 20 pounds of grass seed cover?
It needs Calculation, Target pure-live-seed rate, Purity, Germination, Plants counted and Length of row sampled. Nothing else is required, and the figures stay in your browser.
How much grass seed per 1000 sq feet?
The result gives Pure live seed, Bulk seeding rate required, Increase over the target rate, Area sampled, Estimated stand population and Units used, each labelled with its unit so the figure can be read on its own.
What information do I need for the grass seed calculator?
You need Calculation, Target pure-live-seed rate, Purity, Germination, Plants counted, Length of row sampled, Row spacing and Rows sampled. The page opens with default figures that give bulk seeding rate required of 13.586957, so you can see the scale before entering your own.
What does this grass seed calculator show?
It shows Pure live seed, Bulk seeding rate required, Increase over the target rate, Area sampled, Estimated stand population and Units used, with the working and any warnings for your entries.