What is thousand-kernel weight (TKW)?

TKW is the weight in grams of 1,000 seeds of a given crop and variety. It varies between varieties, growing seasons, and seed lots. It is typically printed on certified seed bags or measured in a lab. Higher TKW means larger seeds, requiring more kg/ha to achieve the same plant density.

What is field establishment percentage?

Field establishment (also called field emergence or seedling survival rate) is the percentage of germinated seeds that survive to become established plants. It accounts for losses from soil crusting, pests, disease, moisture stress, and other field factors. Typical values range from 75% to 90% for good conditions.

How does germination % differ from establishment %?

Germination % (from the seed tag) reflects laboratory germination under ideal conditions. Field establishment % is lower because it accounts for real-world losses after germination. Both factors reduce the effective plant density you achieve per kg of seed sown.

What is the formula used?

Seed Rate (kg/ha) = (Target Density × TKW) / (Germination % / 100 × Establishment % / 100 × 1000). The division by 1000 converts grams to kilograms. Multiplying by field area gives total seed needed.

Can I use seeds per acre instead of per m²?

Yes. Select "per acre" as the density unit. The calculator converts internally (1 acre = 4,046.86 m²) before applying the formula and presents results in both kg/ha and kg/acre.

Why do the crop presets differ so much in density?

Each crop has an optimal plant spacing determined by its growth habit, canopy architecture, and yield response. Corn is typically planted at 7–8 plants/m² while wheat and canola can be planted at 200–350 and 100–150 plants/m² respectively to compensate for tillering and branching.

Seed Rate Calculator

Name: Seed Rate Calculator
Availability: InStock
Author: Nham Vu

Calculate the optimal seeding rate in kg/ha using target plant density, thousand-kernel weight, germination %, and field establishment %.

Seeding Parameters

Crop Preset

Presets populate typical starting values — adjust as needed.

Target Plant Density

Thousand-Kernel Weight (TKW) (grams)

Found on the seed bag or lab certificate.

Germination Rate (%)

From the seed tag (laboratory germination test).

Field Establishment Rate (%)

Expected survival from germination to established plant (75–90% is typical for good conditions).

Field Area (optional)

Enter field size to calculate total seed quantity needed.

Fill in the parameters and click Calculate to see your seeding rate.

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Summary

Calculate the optimal seeding rate in kg/ha using target plant density, thousand-kernel weight, germination %, and field establishment %.

How it works

Select a crop preset (wheat, corn, soybeans, or canola) or enter custom values.
Enter your target plant density (plants per square meter or per acre).
Enter the thousand-kernel weight (TKW) in grams — found on the seed bag or lab report.
Enter the germination percentage from the seed tag.
Enter the expected field establishment percentage to account for environmental losses.
Optionally enter your field area to calculate total seed needed.
Click Calculate to see the seeding rate in kg/ha and total seed required.

Use cases

Determine the correct seed bag quantity to order before planting.
Adjust seeding rates when using seed lots with lower germination.
Compare seeding rates across different crop varieties and TKW values.
Convert between seeds/m² and kg/ha for agronomic planning.
Account for poor seedbed conditions by adjusting establishment %.
Optimize input costs by avoiding over-seeding or under-seeding.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu