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Seeding Rate Calculator (seeds per m²)

The seeding rate calculator helps you plan seed purchases and prepare your garden or field for planting. Enter the area to be sown in square metres, the seeding rate in grams per square metre, and optionally the thousand seed weight and germination rate — the calculator will instantly show the total seed quantity in grams and kilograms, as well as the estimated number of seeds and plants expected after germination. Accurate seed planning is critical for good yields and cost efficiency. Too few seeds result in sparse stands and poor harvests, while too many waste money and can cause plants to compete for water and nutrients. Seeding rates vary widely by species: lawn grass typically requires 20–30 g/m², radishes 2–3 g/m², carrots 1–2 g/m², and peas 15–25 g/m².

Reviewed byRedakcja Liczbnik
Calculator
m²
g/m²
g
%
Seeding Calculation ResultSeed quantity (g)20
Seed quantity (kg)
0.02
Number of seeds
4,000
Expected plants
3,600
Germination rate
90%

How we calculate seeding

Seed quantity (g) = seeding rate (g/m²) × area (m²). Seed quantity (kg) = seed quantity (g) / 1,000. Number of seeds = (seed quantity in g / thousand seed weight in g) × 1,000. Expected plants = number of seeds × germination rate / 100. Results are rounded to 2 decimal places (grams and kg) or to whole numbers (seeds and plants).

Example: lawn 50 m², seeding rate 25 g/m²

Area 50 m², seeding rate 25 g/m²: seed quantity = 50 × 25 = 1,250 g = 1.25 kg. With a thousand seed weight of 2 g for grass: number of seeds = (1,250 / 2) × 1,000 = 625,000 seeds. At 85% germination rate: expected plants = 625,000 × 0.85 = 531,250 seedlings.

Frequently asked questions

What is a seeding rate and how is it measured?

A seeding rate is the amount of seed sown per unit area, typically expressed in grams per square metre (g/m²) or kilograms per hectare (kg/ha). It varies by species, soil conditions, and desired plant density.

How many grams of grass seed do I need per m²?

For a lawn, the standard seeding rate is 20–30 g/m² for new seeding and 5–10 g/m² for overseeding an existing lawn. High-traffic areas may require the higher end of the range.

What is thousand seed weight (TSW)?

Thousand seed weight (TSW) is the weight in grams of exactly 1,000 seeds of a given species. It is used to convert seed weight to the number of individual seeds. TSW varies greatly: grass seeds may weigh 1–5 g/1000, while pea seeds may weigh 100–300 g/1000.

What is germination rate and how does it affect seeding calculations?

Germination rate is the percentage of seeds that successfully sprout under ideal conditions. If germination rate is 85%, then 85 out of every 100 seeds planted will germinate. A lower germination rate means you may need to sow more seed to achieve the desired plant density.

How do I convert g/m² to kg/ha?

Multiply the rate in g/m² by 10 to get kg/ha. For example, 25 g/m² = 250 kg/ha. This is because 1 hectare = 10,000 m², and 1 kg = 1,000 g, so the conversion factor is 10,000/1,000 = 10.

Can I sow too many seeds?

Yes. Over-seeding causes overcrowding, where plants compete for light, water and nutrients. This can lead to weak, spindly plants and increased susceptibility to disease. Always follow the recommended seeding rate for the species.

Indicative result

Results are estimates for informational purposes only. Actual yields depend on soil quality, weather conditions, plant variety and cultivation methods. Always consult the seed manufacturer's current recommendations.

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