Seed Germination Rate Calculator

Germination rate is the percentage of seeds that successfully sprout, and it decides how many you need to sow to end up with the plants you actually want. Sow to your target count and you will be short; sow blindly and you will spend an evening thinning a tray of two hundred lettuces.

What Affects Germination Rate?

Germination rate depends on several factors:

• Seed quality and age: Fresh seeds from reputable suppliers germinate at 80–95% for most vegetables. Seeds stored more than 2–3 years may drop to 50–60%.
• Species: Some plants germinate reliably (lettuce, beans, peas: 90%+), while others are more variable (parsley, peppers: 60–75%).
• Soil temperature: Most seeds germinate within a specific temperature range. Outside this range, germination slows dramatically or fails.
• Moisture: Seeds must absorb water (imbibition) to activate germination. Inconsistent moisture is a major cause of germination failure.
• Light/dark requirements: Some seeds need light to germinate (lettuce, basil); others prefer darkness (onions, phacelia). Most are neutral.

Typical Germination Rates by Vegetable

The Germination Rate Formula

Expected Seedlings = Number of Seeds × (Germination Rate / 100)

Seeds Needed for a Target Count = Target Seedlings / (Germination Rate / 100)

What the Seed Age setting does

The age dropdown multiplies your germination rate down, because stored seed loses viability:

Those are averages, and the spread by species is wide enough to matter. Onion, parsnip, leek and parsley are close to dead after a year in a drawer. Tomato, cucumber, squash and brassicas hold up for five years or more if kept cool and dry, and often beat the table above. Cold and dry is the whole trick: a sealed jar in the fridge preserves seed far better than a shed in July.

If you have any doubt, run a rag doll test. Ten seeds on a damp paper towel in a sealed bag on top of the fridge, counted after the days-to-germinate figure above. However many sprout out of ten is your real percentage, and it takes a fortnight rather than a season to find out.

Improving Poor Germination

• Scarification: Scratching hard seed coats (e.g., morning glory) improves water penetration
• Soaking: Pre-soaking beans and peas overnight increases germination speed and rate
• Stratification: Cold-moist stratification breaks dormancy in many perennials and trees
• Fresh seed: Always use seeds within their recommended use-by date

This page works in seeds, which is the right unit for a packet and a tray. Planting by the acre is the same division with one more term in it, field emergence, which is always lower than the lab germination on the tag. The seeding rate calculator takes both and prices the seed order.