Grass Seed Calculator

Lawn area, m²

What you are doing

Lawn type

Pack size, kg

Price a pack

Result

Seed, kg3.5
Sowing rate, g/m²35
Packs4
Cost$2,400.00
With a reserve for patching, kg3.85
What mattersThe rate assumes about 80 percent germination. Sowing thicker does not help: crowded grass comes up weak and burns off first.

Sowing thicker does not make a better lawn

Calculates how much grass seed a lawn needs by area and lawn type, for a new sowing or for overseeding an existing one.

Seeding rates run from about 35 grams a square metre for a universal mix to 50 for a sports lawn, which has to take wear. Overseeding an existing lawn takes roughly half of that, because the seed is only filling gaps.

The temptation is always to add more. Crowded seedlings compete for the same light and water, come up thin and weak, and are the first to burn off in the first dry spell.

What this calculator shows

The seed needed in kilograms and the rate behind it
The number of packs and what they cost
A ten percent reserve for patching thin spots later

What to keep in mind

The rates assume around eighty percent germination, which is normal for fresh seed on prepared soil.
Old seed germinates worse. Two-year-old seed can need a third more to give the same cover.

FAQs

How much seed does a hundred square metres need?

About 3.5 kg for a universal lawn on bare soil, 4 to 4.5 for an ornamental one and 5 for a sports mix.

Why not sow thicker for a denser lawn?

Because density comes from tillering, not from seed count. Overcrowded plants stay spindly, shade each other and thin out within a season.

When is the best time to sow?

Late summer to early autumn in most climates: warm soil, more rain and fewer weeds competing. Spring works too but needs watering.

Does overseeding need soil preparation?

Scarify first so the seed reaches soil rather than sitting on thatch. Seed that never touches earth simply feeds the birds.

Worked example

A hundred square metres

Input: 100 m², a new lawn, a universal mix, 1 kg packs

Output: 3.5 kg, four packs

Note: Overseeding the same area would take 1.75 kg. A sports mix would take 5 kg, because it is sown denser to survive being walked on.

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All tools in Home & Utilities

Grass Seed Calculator

Result

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