Germination Rate Calculator
Test seed viability and adjust the sowing rate for pure live seed.
Please note: Planning figures based on published averages. Soil type, climate, variety, season and local practice all shift these results substantially. Base real decisions on a soil test, local extension guidance and the product label — particularly for fertiliser, lime and any crop protection product, where the label is a legal document.
What the Germination Rate Calculator does
A germination test counts how many seeds from a sample actually sprout. Combined with purity — the share of the bag that is crop seed at all — it gives pure live seed, which is the fraction of what you sow that can genuinely become a plant.
Formula
Germination % = Germinated ÷ Tested × 100Pure live seed = Germination % × Purity % ÷ 100Adjustment factor = 100 ÷ Pure live seedAdjusted rate = Base rate × Adjustment factor
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Seeds tested | number | Yes | Accepts 1 or more. |
| Seeds that germinated | number | Yes | Accepts 0 or more. |
| Seed purity | % | Optional | The share of the sample that is the crop seed rather than chaff or weed seed. |
| Sowing rate at 100% pure live seed | kg/ha | Optional | Accepts 0 or more. |
| Area to sow | number | Yes | Accepts more than 0. |
| Area to sow unit | one of 4 options | Yes | — |
How to use it
- Choose Area to sow unit.
- Enter Seeds tested, Seeds that germinated and Area to sow.
- Optionally add Seed purity and Sowing rate at 100% pure live seed.
- Select Calculate.
Worked example
92 of 100 seeds germinated, with 98% purity.
- Tested
- 100
- Germinated
- 92
- Purity
- 98%
92% germination × 98% purity = 90.16% pure live seed, so the sowing rate needs multiplying by 1.109 — about 11% more seed.
Frequently asked questions
How many seeds should I test?
At least 100 for a rough check. Certified testing uses 400 seeds in four replicates of 100, which keeps the sampling error acceptable.
Can I just sow more of a poor batch?
Up to a point. Below about 70% germination the surviving seedlings tend to be weak as well as few, and fresh seed is usually the better economics.