Lawn Seed Calculator

Calculate how much grass seed you need for a given area — with typical rates for common species.

How to use

  1. Enter the area to be seeded in m².
  2. Enter the seed rate in g/m² — check the seed bag or use the reference rates shown.
  3. The total seed needed appears in kg and grams.

About this tool

The seed rate depends on the grass species, the seed size and whether you are establishing a new lawn or overseeding an existing one. Bermuda grass needs only 10-15 g/m² because the seeds are tiny; perennial ryegrass needs 30-40 g/m² because the seeds are larger and heavier.

Overseeding typically uses half the establishment rate. For renovation of bare patches, use the full rate. These are the manufacturer rates — the tool calculates the total from whatever rate you enter.

A common mistake is underseeding. Thin coverage lets weeds establish. Better to use the recommended rate and accept a slightly higher seed cost than to fight weeds for months.

The formula

Seed (grams) = area (m²) × rate (g/m²). 1 kg = 1,000 g.

Frequently asked questions

Should I overseed at the same rate?

No — overseeding typically uses 50-60% of the establishment rate, because existing grass fills some of the space.

Does germination rate affect the calculation?

Yes — if germination is 80%, you need 25% more seed. Most commercial seed has 85-95% germination.

When is the best time to seed?

For warm-season grasses (bermuda, zoysia): spring. For cool-season (ryegrass, fescue): autumn.

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