Seed Rate Calculator
Turn your row and plant spacing into the seeds to sow, allowing for germination, and the weight of seed to buy.
Part of the 🌾 Farmers toolkit, with more tools made for the job.
The share of seeds you expect to become plants.
Leave empty for 100%.
Leave empty to see the rate for one.
Shown on the seed bag. Gives the seed weight.
Type the row and plant distances and the germination rate, and the seed you need appears here.
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Type the distance between rows, the distance between plants and the germination rate, and this works out how many seeds to sow per hectare or acre. Add the weight of 1,000 seeds from the bag to get the weight to buy.
Not every seed becomes a plant, so you sow more than the number of plants you want. A germination rate of 90% means you need about 11% more seeds than plants.
How it’s worked out
- Plants wanted per hectare is 100,000,000 divided by the row spacing times the plant spacing, both in centimetres. Per acre it is 6,272,640 divided by the two spacings in inches.
- Seeds to sow is the plants wanted divided by the germination rate and the purity, as fractions of 1.
- Seed weight is the number of seeds times the weight of 1,000 seeds, divided by a million, in kilograms. Pounds are shown for imperial.
Rows 75 cm apart with a plant every 25 cm gives 53,333 plants per hectare. At 90% germination you sow 59,259 seeds per hectare. With seeds weighing 300 g per 1,000, that is about 17.8 kg per hectare.
Common mistakes
- Using the germination figure from the bag label when the seed is old. Test your own seed if you can.
- Forgetting field losses. Pests, crusting and wet soil can mean fewer plants than germination alone suggests, so some growers use a lower figure.
- Mixing units, for example row spacing in centimetres and plant spacing in inches.
- Ignoring purity. A bag that is 98% pure seed is not all seed.
Questions
What does "germination and emergence" mean here?
The share of sown seeds you expect to become plants. Some extension methods add a separate allowance for seedling losses in the field. Here you can build that in: if you expect field emergence to be lower than the lab germination, type the lower figure.
Where do I find the weight of 1,000 seeds?
It is often on the seed bag or the variety sheet as thousand seed weight (TSW or 1,000 kernel weight). It is optional here.
Does this tell me the right plant population?
No. It works out the seed for the spacing you choose. The right spacing and population depend on your crop, soil and local advice.
Where the method comes from
Estimates only
These are estimates and general information, not agronomic, financial or professional advice. Rates, timings and costs depend on your crop, land, weather and local rules.
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