Seed Storage Life Calculator & How Long Seeds Last
Estimates life of vegetable seed
Find how long your seed stays viable — pick a crop and enter the storage temperature, seed moisture and humidity to estimate the years of life, with the rule-of-100 safe-storage check.
Enter your seed & store
Next: the store is too warm/humid — dry the seed and lower temperature or humidity until °F + %RH drops below 100, or seed will lose viability fast.
Rough guide; real life varies by species, seed quality and storage.
Seed storage — key facts
- −1% moisture
- ≈ doubles life
- −5.6 °C
- ≈ doubles life
- Rule of 100
- °F + %RH < 100
- Onion / leek
- ≈ 1 year
- Beans / carrot
- ≈ 3 years
- Cucumber / melon
- ≈ 5+ years
- Best store
- cool, dry, airtight
- Privacy
- Runs in your browser; nothing uploaded
Cool and dry seed lasts for years
Seed is a living thing, slowly using up its reserves until it can no longer germinate. How fast that happens is governed mostly by two things — temperature and moisture — captured in Harrington's famous rules: every 1% drop in seed moisture, and every 5.6 °C drop in temperature, roughly doubles storage life. Get both right and seed that would fade in a year can last many.
This tool takes each crop's natural longevity and adjusts it for your storage temperature, seed moisture and humidity, then runs the quick "rule of 100" safe-storage check (°F + %RH should stay under 100). Use it to decide whether last year's seed is worth sowing, to plan how to store saved seed, or to justify a sealed, cool store. Always germination-test old seed before relying on it — pair this with the Seed Germination Test tool.
Use old seed wisely
Estimate whether last season's seed is still worth sowing.
Store it right
See how cool & dry storage multiplies seed life.
Pass the rule of 100
Quick check that your store isn't too warm or humid.
Plan by crop
Short-lived onions vs long-lived cucurbits, at a glance.
Frequently Asked Questions
How long do seeds stay viable?+
It depends on the species and storage conditions. At cool, dry storage, onion and leek seed last about a year, carrots and beans 3 years, tomatoes and brassicas 4, and cucumbers/melons 5+. This tool gives an estimate for your crop adjusted for your temperature, seed moisture and humidity.
What are Harrington's rules of thumb?+
Two practical rules for seed storage: (1) storage life doubles for each 1% decrease in seed moisture content (within roughly 5–14%), and (2) storage life doubles for each 5.6 °C (10 °F) decrease in temperature. So cooler and drier dramatically extends seed life. This tool applies both to the crop's baseline life.
What is the 'rule of 100'?+
A quick safe-storage check: the storage temperature in °F plus the relative humidity in % should stay below 100. For example, 50 °F + 40% RH = 90 (good), but 70 °F + 50% RH = 120 (poor). The tool computes this and flags whether your conditions pass.
What is the best way to store seeds?+
Dry the seed well, then keep it cool and dry in an airtight container (add a desiccant like silica gel). A sealed jar in a fridge is excellent for long-term storage. Cool + dry + airtight is the trio that maximises viability; warmth and humidity are the enemies.
Does seed moisture really matter that much?+
Yes — it's one of the two biggest factors. Each 1% of extra moisture roughly halves storage life, and damp seed also moulds and respires faster. Dry seed to a low, safe moisture (typically 5–8% for storage) before sealing it away.
Can I freeze seeds?+
Most orthodox crop seeds can be frozen if they're dry enough (low moisture) — freezing greatly extends life, which is how seed banks store germplasm for decades. Let frozen seed warm to room temperature in its sealed container before opening, to avoid condensation. Don't freeze high-moisture or recalcitrant seeds.
How do I know if old seed is still good?+
Run a germination test: count how many of a sample sprout on damp paper. The Seed Germination Test tool turns that into a percentage and an adjusted seed rate. Even viable old seed often germinates slower and weaker, so test before sowing a whole field.
Why do some seeds last longer than others?+
Seed longevity is largely genetic and linked to seed chemistry — oily seeds and thin-coated seeds (onion, parsnip, sweetcorn) are short-lived, while harder, starchy or well-protected seeds (beans, brassicas, cucurbits) last longer. The tool's baseline reflects these species differences.
Does this guarantee my seed will germinate?+
No — it's a planning estimate based on rules of thumb. Actual viability also depends on the seed's starting quality, how it was harvested and dried, and pests in storage. Treat the figure as a guide and always germination-test before relying on stored seed.
How should I label stored seed?+
Mark each container with the crop, variety and the year harvested or purchased. Knowing the age lets you use older seed first and predict viability with this tool. Store the oldest seed at the front so it's used before it declines.