Grass Seed Quantity Calculator

Work out grass seed quantity instantly with clear inputs, formula shown and shareable results.

About Grass Seed Quantity Calculator

Seeding rate is 25-35 g per square metre for a new lawn, around 70% of that for overseeding into existing grass, and considerably more for patch repair where competition is absent. Sowing too heavily causes damping off as seedlings compete.

Formula

Seed quantity

seed (kg) = area x rate (g/m2) / 1000, with the rate adjusted for the purpose

Worked example

With the default values below, Grass Seed Quantity Calculator returns Seed required of 4.20. Change any input above and every figure here is recalculated in your browser.

Inputs used

Area to seed: 120 m²
Seeding rate: 35 g/m²
Purposeone of New lawn, Overseeding an existing lawn, Repairing bare patches: New lawn
Bag size: 5 kg

Results

Seed required: 4.20 kg
Bags needed: 1 bags
Rate applied: 35.00 g/m²
Area covered per bag: 142.86 m²

Step by step

1Values used
2Seed quantity
3Seed required= 4.20 kg
4Bags needed= 1 bags
5Rate applied= 35.00 g/m²
6Area covered per bag= 142.86 m²

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Can I sow more heavily for a thicker lawn?

No. Overcrowded seedlings compete for light and water, producing weak grass prone to fungal disease. Correct rate plus good preparation gives a denser lawn.

When is the best time to sow?

Early autumn is ideal — warm soil, reliable moisture and little weed competition. Spring works but needs more watering.