Formula Used
Planting Positions = Effective Area ÷ (Plant Spacing × Row Spacing) Base Seeds = Planting Positions × Seeds Per Position Adjusted Seeds = Base Seeds ÷ Combined Establishment Factor Combined Establishment Factor = Germination × Purity × Emergence × Survival × Transplant Success × (1 − Loss) Adjusted Seeds With Allowances = Adjusted Seeds × (1 + Safety Margin + Replanting Reserve) Seed Weight = Required Seed Count ÷ Seeds Per Weight Unit Packets Required = Ceiling(Required Seeds ÷ Seeds Per Packet) Seed Quantity From Rate = Effective Area × Seed Rate
Percentages become decimals before multiplication. Packet and bag totals always round upward. Confirm crop recommendations with a reliable local source.
How to Use
- Select the calculation method matching your planting plan.
- Enter area, spacing, rows, rate, or tray information.
- Add germination, purity, emergence, and survival percentages.
- Provide seed weight, packet, or bag details.
- Choose output precision, then calculate the requirement.
- Review warnings before ordering or distributing seed.
Example Data
| Scenario | Area | Spacing or rate | Quality assumptions | Typical use |
|---|---|---|---|---|
| Vegetable bed | 100 m² | 20 × 50 cm | 90% germination | Transplanted vegetables |
| Wheat field | 1 hectare | 125 kg/hectare | 90% germination | Field seeding |
| Lawn repair | 250 m² | 35 g/m² | 85% germination | Broadcast seeding |
| Nursery trays | 10 trays | 72 cells each | 85% emergence | Plug production |
Frequently Asked Questions
Why adjust for germination?
Not every seed produces a plant. Germination adjustment covers expected failures. Better test results improve the estimate.
What does seed purity mean?
Purity estimates usable seed within the lot. Debris and other seeds reduce purity. Use the label value when available.
Should packets round upward?
Yes, partial packets cannot usually be purchased. The calculator uses upward rounding. This prevents under-ordering seed.
Can I calculate broadcast seed?
Yes, choose the broadcast method. Enter a weight rate per area. A small distribution allowance is included.
How are paths handled?
Bed and path widths create a planting factor. Wider paths reduce usable planted area. Leave both blank to ignore paths.
What is thousand-seed weight?
It is the mass of one thousand seeds. It converts seed counts into weight. Use clean, representative seed samples.
Can I use imperial units?
Yes, imperial and metric units are supported. Inputs convert internally before calculation. Results use your chosen weight unit.
Why can expected plants exceed the target?
Safety and reserve percentages add extra seed. Actual establishment may then exceed targets. Thin plants when agronomically appropriate.
Are crop presets guaranteed?
No, presets are planning examples only. Rates vary by variety and climate. Follow local agronomic recommendations.
How should old seed be handled?
Test germination before using older seed. Enter the measured percentage here. Increase reserves only when justified.
Can results replace professional advice?
No, results support preliminary planning. Soil, weather, and machinery affect outcomes. Consult a qualified local adviser.