Seed Rate Calculator
Calculate the total seeds required and seed weight for a planting area, adjusted for germination rate and thousand grain weight (TGW).
Results
What is it?
The seed rate calculator determines how many seeds to purchase and how much they will weigh, accounting for less-than-perfect germination. The adjusted seed rate = target density ÷ germination rate. Weight = (total seeds / 1,000) × TGW (g) / 1,000.
How to use
Select the planting area and unit (hectares, acres, or m²). Enter your target plant density in seeds per m², the seed germination rate from the label, and the thousand grain weight (TGW) from the seed specification. The calculator returns total seeds needed and weight in both kg and lbs.
Example scenario
Planting 1 hectare of wheat at 300 seeds/m² with 85% germination and TGW of 45 g: Adjusted rate = 300/0.85 = 353 seeds/m². Total = 353 × 10,000 = 3,529,412 seeds. Weight = (3,529,412/1000) × 45/1000 = 158.8 kg ≈ 350 lbs of seed.
Pro tip
Higher TGW seeds generally produce more vigorous seedlings. Some agronomists recommend a 5–10% additional buffer beyond the germination adjustment to account for soil conditions, pest pressure, and seedbed preparation quality. Store seed in cool, dry conditions — germination rates decline 2–5% per year in poor storage.