Seeding rate calculator
Sowing by weight without knowing the thousand-grain weight is guessing. Seed size varies by a third between lots of the same variety.
per m2
g
%
%
Seed rate
208.0kg/ha
- Seeds to sow per square metre
- 433.4
- Seeds per hectare
- 4 334 365
- Seed for the whole area
- 8.322 tonnes
- Seed cost per hectare
- 99.86
- Total seed cost
- 3994.55
- Seeds per kilogram
- 20 833
- Seed spacing at 12.5 cm rows
- 1.85 cm
Show the working
- Target plants = 350
- Thousand grain weight = 48
- Germination = 95
- Field establishment = 85
- Area = 40
- Seed price per tonne = 480
- Seeds to sow per square metre = 350 / (95/100) / (85/100) = 433.437
- Seeds per hectare = 433.437 * 10000 = 4 334 370
- Seed rate = 4 334 370 * 48 / 1e6 = 208.05
- Seed for the whole area = 208.05 * 40 / 1000 = 8.321 98
- Seed cost per hectare = 208.05 / 1000 * 480 = 99.8638
- Total seed cost = 99.8638 * 40 = 3994.55
- Seeds per kilogram = 48 > 0 ? 1e6 / 48 : 0 = 20 833.3
- Seed spacing at 12.5 cm rows = 433.437 > 0 ? 100 / (433.437 * 0.125) : 0 = 1.845 71
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- seeds to sow = target population / (germination x establishment)
- rate in kg/ha = seeds per hectare x thousand grain weight / 1 000 000
Establishment falls with late drilling, a rough seedbed and cold, wet soil. Raising the seed rate is the usual compensation.