Seed Rate Calculator
Kilograms mean nothing without a thousand-grain weight.
Work out Seed Rate. Kilograms mean nothing without a thousand-grain weight. Shows the working, not just the answer.
Seed rate
185.3 kg/ha
412 seeds/m² for 350 plants at 85% establishment
Seed rate in kilograms is meaningless without a thousand-grain weight. The same variety can run from 38 g to 55 g between seasons, which is a 45% swing in kilograms for an identical target population — and it is the number most often left out of a recommendation. Establishment is the other half. Drilling into a rough seedbed in November establishes far worse than into a fine one in September, and the rate has to rise to compensate. Assuming 95% when the field delivers 60% leaves the crop a third short. Target population is agronomy, not arithmetic. It depends on crop, variety, drilling date, region and what the crop is for, and the figure here is whatever you enter — a starting point from your own agronomist rather than a recommendation from a web page.
How the Seed Rate Calculator works
Seed rate in kilograms per hectare from target plant population, thousand-grain weight and establishment, with total seed, bags and cost. TGW is the input most recommendations leave out and the one that varies most.
Also known as: how much seed per hectare · seed rate from thousand grain weight · drilling rate for wheat · seeds per square metre calculator
Frequently asked questions
How do you calculate a seed rate?
Target plants per m² ÷ establishment %, times thousand-grain weight in grams, divided by 100. That gives kilograms per hectare directly.
What is thousand-grain weight?
The weight of 1,000 seeds in grams. It sets how many seeds are in a kilogram, and it varies by a third or more between varieties and seasons for the same crop.
Why does the same seed rate give different plant counts?
Because TGW changed. The same 185 kg/ha delivers 412 seeds/m² at 45 g TGW and 336 at 55 g — a 20% difference in population from nothing but seed size.
What establishment percentage should I use?
Whatever your own fields deliver. A fine seedbed in good conditions might give 90%; late drilling into a rough or wet seedbed can fall below 60%, and the rate has to rise to compensate.
What target population should I aim for?
That is agronomy, not arithmetic — it depends on crop, variety, drilling date, region and end use. This page takes whatever figure your agronomist gives you.
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