Inputs
Pick a species by common name, or work from seeds you counted yourself.
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Model Scope / Use At Your Own Risk
This calculator applies published seed-count tables and Harrington's storage rules of thumb. It estimates how long orthodox seed stays viable under dry storage. It does not test your seed, does not know your seed lot, and cannot tell you whether a specific packet will germinate.
Storage-life figures are projections from thumb-rules. The only way to know whether seed is still good is a germination test: 20 to 100 seeds on damp paper towel at the species' optimum temperature.
Recalcitrant and intermediate species are refused by design, because dry-storage models do not apply to them. A refusal is an answer.
No warranty. No liability. No suitability claim. You assume all risk. Provided as-is without warranty of accuracy, completeness, merchantability, fitness for a particular purpose, agricultural suitability, or commercial value. The creators and maintainers disclaim responsibility for crop failure, germination loss, seed-bank decisions, commercial losses, or any other consequence arising from use or misuse of this page.
Verify independently. Check the cited sources and run a germination test before relying on any result for a planting, a seed bank, or a commercial decision.
How To Use This Tool
This tool answers three separate questions. Mixing them up is the usual source of confusion.
- How many seeds are in this packet? Search the species, read the seeds-per-ounce card. If two sources disagree the tool shows both and does not average them: averaging a transcription error with a correct value produces a number that is wrong and looks authoritative.
- How many seeds do I actually have? Weigh a sample, count it, and enter both under Count. A measured count beats every table here. Published counts carry cultivar, seed-lot and cleaning-standard variation; your own packet has none of that. The published range then becomes a cross-check.
- How long will this seed keep? Set the storage temperature and moisture. The multiplier is relative to the baseline conditions the published longevity figure is assumed to describe, so the baseline is an editable input.
Moisture content and relative humidity are different quantities. Seed moisture content is water as a percentage of seed weight, typically 5 to 14% in stored seed. Relative humidity describes the air around the seed. Harrington's moisture rule uses moisture content; the Hundred Rule uses relative humidity. Both therefore appear as inputs.
Freezer storage is outside these rules. Harrington's thumb-rules are only valid between 0 and 40 °C. Ask for -18 °C and the tool clamps to 0 °C and says so. Genebank conditions need the Ellis-Roberts viability equation, which this version does not include.
The tool will refuse some species. Acorns, chestnuts, avocado and mango have recalcitrant seed that dies on drying; garlic and potatoes are not grown from stored seed at all. In both cases the tool withholds the storage-life model and explains why. Seed counts still display.
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Count your own sample
Your packet
Published counts for this species
| Source | Listed as | Seeds / oz | Seeds / lb |
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