Germination Test Calculator

Seed germination percent, verdict, and sowing multiplier from sprouted count.

What it does

Old seed loses sprout before it loses looks: a damp towel test of ten seeds tells the truth in a week. Eight sprouts means 80% and thicker sowing; fewer than seven means fresh packets.

The tool above takes sprouted count with seeds tested. It returns the germination percent with a verdict and the compensating sowing rate beside them.

The default of 8 from 10 gives 80%: good, sow 1.25x normal. Ten from 10 gives 100%: plant normal, while 5 from 10 gives 50%: buy fresh seed.

The rules follow extension seed testing guides with a second extension program matching each line. Both test ten seeds on towels and buy fresh below 70%.

How to use

1. Lay ten seeds on a damp towel in a bag.
2. Wait the packet germination days in warmth.
3. Count sprouted seeds honestly.
4. Enter sprouted with ten tested.
5. Read the verdict before sowing day.

Formula

10

Test seeds making percent instant.

70%

Buy fresh line for old seed.

multiplier

Normal rate divided by germination share.

Home test only; certified labs run replicated official trials. Weak sprouts count only when strong; stunted seedlings rarely produce.

Worked example

Reference table

Limits

• Home estimate only; labs certify officially.
• Vigor beyond sprouting stays untested.
• Old seed varies packet to packet.
• Moldy towels ruin tests, not seeds.

Common mistakes

• Testing five seeds and trusting the percent.
• Culling ugly seeds before testing.
• Drowning towels instead of dampening.
• Sowing normal rates on weak lots.
• Keeping seed packets for a decade untested.

Try it yourself

Quick checks. Answers sit tucked under each question.

Questions

Sources

• Illinois Extension: Seed viability and germination (PDF)
• UW-Madison Extension: Testing seed viability (Dane County)

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