Seed Rate Calculator Widget
Agronomy sites and seed dealers can let growers turn a target plant stand into a drill setting. Readers enter the plants they want, the thousand-seed weight from the certificate and expected germination and establishment, and get kg per hectare (or lb per acre), seeds per square metre and the seed for the whole field.
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<iframe src="https://a2z.tools/embed/w/seed-rate-calculator" title="Seed Rate Calculator by A2Z Tools" width="100%" height="600" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>
A plain iframe. Works everywhere, including site builders that strip scripts. Adjust height if your content needs more room.
<div data-a2z-widget="seed-rate-calculator" data-height="600"></div> <script async src="https://a2z.tools/embed.js"></script>
Adds a small script (what it does) that sizes the widget to fit its content, loads it lazily and keeps it isolated from your page's CSS.
Works with
How it works
Sowing by weight alone ignores seed size: a lot with large seeds needs more kilograms to deliver the same number of plants. The calculation starts from the target population, divides it by the germination percentage and by the share of germinated seeds expected to establish in the field, and gives the seeds to sow per square metre. Multiplying by the thousand-seed weight (TSW) in grams and dividing by 100 converts seeds per m2 into kilograms per hectare; imperial figures use plants per square foot and lb/acre (1 kg/ha = 0.8922 lb/acre). For wheat at 250 plants/m2, TSW 45 g, 95% germination and 80% establishment that is 329 seeds/m2 and 148 kg/ha. The Canola Council of Canada example of 6 plants/ft2, a 6 g TSW and 60% emergence comes out at 5.8 lb/acre; the same target with 4 g seed needs only 3.8.
Calculation method
- Seeds to sow per m2 = target plants per m2 / (germination % / 100 x establishment % / 100)
- Seed rate (kg/ha) = seeds per m2 x thousand-seed weight (g) / 100
- lb/acre = kg/ha x 0.892179; plants per ft2 x 10.7639 = plants per m2
- Seed for the field = rate x area
Worked examples
Canola Council example
Inputs: 6 plants/ft2; TSW 6 g; germination 100%; establishment 60%
Result: 5.8 lb/acre (6.5 kg/ha); 10 seeds per ft2
6 / 0.6 = 10 seeds per ft2 = 107.6 per m2 x 6 g / 100 = 6.46 kg/ha = 5.76 lb/acre.
Winter wheat, 10 ha field
Inputs: 250 plants/m2; TSW 45 g; germination 95%; establishment 80%; 10 ha
Result: 148 kg/ha; 329 seeds/m2; 1,480 kg for the field
250 / 0.76 = 328.9 seeds; x 45 / 100 = 148.0 kg/ha.
Limitations
- Establishment is an estimate the grower must supply; the result is only as good as that guess.
- Does not recommend a target population for any crop or region.
- Drill calibration still needs a check on the machine - seed flow varies with seed shape and treatment.
Where publishers use it
- A seed company's variety page where TSW differs between lots
- An agricultural extension bulletin on adjusting cereal seed rates for late sowing
- A canola or oilseed-rape growers' association page on plant stand targets
- An agronomy course exercise on seed size, germination and establishment
- A farm-management software blog post on variable-rate seeding
Questions
What is thousand-seed weight and where do I get it?
TSW is the mass in grams of 1,000 seeds. It is usually printed on the seed certificate or bag; otherwise count 1,000 seeds (or 4 x 250) and weigh them. Wheat is often 35-50 g, canola 3-7 g and maize several hundred grams.
What is the difference between germination and establishment?
Germination is measured in the lab under ideal conditions. Establishment is the share of those germinating seeds that become plants in your field, which drops with poor seedbeds, cold soil, pests or deep sowing. The two are multiplied together.
Why does seed size change the rate so much?
Because the rate is a count of seeds expressed as weight. In the Canola Council example a 6 g TSW lot needs 5.8 lb/acre while a 4 g lot needs 3.8 lb/acre for the same 6 plants per square foot - a 50% difference from seed size alone.
Can I use it for maize or soybeans sown by seed count?
Yes. The 'Seeds to sow' card gives seeds per hectare or per acre, which is the figure precision planters are set to; the weight is useful for ordering bags.
What target population should I use?
That depends on the crop, region, sowing date and variety. Take it from your local agronomy guide or advisor; this widget converts the target into a rate, it does not choose the target.
Does establishment of 100% make sense?
Rarely. Even good seedbeds lose some seedlings, so establishment values of 60-90% are typical inputs; enter 100% only if you want the theoretical minimum rate.
Sources
- Seeding rate (Canola Encyclopedia) - Canola Council of Canada . Seeding rate from target plant density, thousand-seed weight and expected emergence; worked example 6 g TSW, 6 plants/ft2, 60% emergence = 5.8 lb/acre (4 g = 3.8 lb/acre). Checked 2026-10-01.
Cite or recommend this tool
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A2Z Tools Seed Rate Calculator https://a2z.tools/embed/seed-rate-calculator
<a href="https://a2z.tools/embed/seed-rate-calculator">A2Z Tools Seed Rate Calculator</a>
[A2Z Tools Seed Rate Calculator](https://a2z.tools/embed/seed-rate-calculator)
Seed Rate Calculator by A2Z Tools - https://a2z.tools/embed/seed-rate-calculator
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