Seed Rate Calculator
Calculate seed needed per hectare from target plant population, seed weight, germination and purity.
Seed rate accounts for losses: you must sow more seed than the plants you want, because germination and purity are below 100%. Seed rate (kg/ha) = target plants/m² ÷ (germination × purity) × seed weight ÷ 1000 × 10.
Indicative planning figures based on published research averages. Local soil tests, varieties and weather change actual requirements — confirm with your agronomist or extension officer.
Farmers and agronomists use the free Seed Rate Calculator for an accurate answer in seconds — no formulas to remember, works offline.
About Seed Rate Calculator
Buying the right amount of seed saves money and avoids gappy or overcrowded stands. The seed rate must be higher than the plant population you want, because not every seed germinates (germination %) and not every gram is pure crop seed (purity %). This tool combines your target plants per m², the 1000-seed weight, and the germination and purity percentages to give the seed required per hectare and per acre.
How to use Seed Rate Calculator
- 1Enter your values into the inputs.
- 2Read the headline result and the supporting breakdown.
- 3Apply the guidance in the note to your decision.
Why use Seed Rate Calculator?
- ✓Uses the standard, citable agronomy formula
- ✓Clear inputs with sensible defaults
- ✓Instant result with the working shown
- ✓Free, fully in-browser and private
Frequently asked questions
How do I calculate seed rate per acre?+
Divide the target plants/m² by the establishment fraction (germination × purity), multiply by the 1000-seed weight ÷ 1000 for grams/m², then ×10 for kg/ha and ×0.4047 for an acre. Lower germination or purity raises the seed rate.
Why sow more seed than the plants I want?+
Because germination is rarely 100% and seed lots contain some inert matter and other-crop seed (purity below 100%). Dividing by the establishment fraction compensates so you still reach the target plant population in the field.
Is this tool free and private?+
Yes — free, no sign-up, and all calculation runs in your browser, so it works offline and your data never leaves the device.
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