Work out how much seed to sow. This free seed rate calculator turns area and sowing rate into total seed in kg or g, across hectares, acres and m², with an optional seed count from thousand-grain weight.
Area & rate
g
Enter the area to sow and your seed rate. Units convert automatically. Add the thousand-grain weight (TGW) from the seed label to also estimate the number of seeds.
Total seed needed
—
Enter area & rate
Area (ha)
—
Rate (kg/ha)
—
Total seed
—
Seeds (approx)
—
Total seed = area × sowing rate. The right rate depends on the crop, variety, soil, season and target plant population — follow agronomic guidance or the seed label. Thousand-grain weight (TGW) converts kilograms to an approximate seed count.
Use this free seed rate calculator to work out how much seed you need. Enter the area and sowing rate to get the total seed, in any common units, plus an optional seed count.
What this seed rate calculator does
A seed rate calculator multiplies your area by the sowing rate to give total seed needed. It converts between hectares, acres, m² and ft², and rates in kg/ha, g/m² or lb/acre.
How seed quantity is calculated
total seed = area × sowing rate
seeds ≈ (total kg × 1,000,000) ÷ thousand-grain weight (g)
So 2 hectares at 120 kg/ha needs 240 kg of seed; a 100 m² lawn at 35 g/m² needs about 3.5 kg.
Typical sowing rates
Crop
Rough rate
Lawn / grass
25–50 g/m²
Wheat
120–200 kg/ha
Barley
120–180 kg/ha
Clover / forage
10–25 kg/ha
Using thousand-grain weight
The thousand-grain weight (TGW) — the weight of 1,000 seeds, printed on most seed labels — lets you convert kilograms into a seed count, useful for hitting a target plant population per square metre.
How to use the seed rate calculator
Enter the area and its unit.
Enter the sowing rate and its unit.
Add TGW for an estimated seed count.
Seed Rate FAQ
How do I calculate how much seed I need?
Multiply the area by the sowing rate. Two hectares at 120 kg/ha needs 240 kg of seed; a 100 m² lawn at 35 g/m² needs about 3.5 kg.
What is seed rate?
It's the amount of seed sown per unit of area — for example kg per hectare or grams per square metre — chosen to reach a target plant population.
What is thousand-grain weight?
TGW is the weight of 1,000 seeds, shown on seed labels. It lets you convert a weight of seed into an approximate number of seeds.
How much grass seed do I need for a lawn?
Around 25–50 g per square metre for new lawns. A 100 m² lawn at 35 g/m² needs about 3.5 kg.
Why does the right rate vary?
Crop, variety, soil, season, drill calibration and target population all affect it. Use the calculator with agronomic guidance or the seed label.
Is the seed rate calculator free?
Yes, this seed rate calculator is completely free, needs no sign-up, and gives instant results in your browser.
