Grass Seed Calculator
Calculate how much grass seed you need for a new lawn or overseeding, based on area and recommended rate per square meter — or the other way around: how large an area a given amount of seed will cover.
How to use the grass seed calculator
- Enter the length and width of the lawn to be seeded.
- Choose the right seed rate — a new lawn needs more seed than overseeding an existing lawn.
- The calculator shows how much grass seed you need in total, in grams and kilograms.
How the seed amount is calculated
The calculator multiplies the area by the recommended amount of grass seed per square meter:
To sow a brand-new 60 m² lawn at 25 g/m², you need 60 × 25 = 1,500 g, i.e. 1.5 kg of grass seed.
The "How large an area can I cover?" tab flips the calculation around: you enter how much grass seed you have on hand, and the calculator works out the largest area it will cover.
Seed mixture and sowing time decide the result
The quantity of seed per square metre is only half the answer — which mixture you sow matters just as much. Mixtures heavy in ryegrass germinate quickly and give green within days, but are less hard-wearing and less winter-hardy over time. Mixtures with meadow grass and fescue take longer to establish but give a denser, more durable lawn. Many ready-made mixtures combine both precisely to get quick cover and good durability at once.
Sowing time decides whether the seed germinates at all. Grass seed needs soil temperature above a certain level and steady moisture during establishment, and sowing late in autumn produces plants that do not have time to root before frost. Late summer and early autumn are often best in cool climates: the soil is warm after summer, and rainfall is more reliable than in late spring.
Frequently asked questions
When is the best time to sow grass seed?
Spring and early fall are generally the best times to sow, when soil temperatures are favorable and competition from weeds is lower. Exact timing depends on your local climate.
Do I need more seed for overseeding than a new lawn?
No, the opposite — overseeding an existing lawn normally needs less seed per square meter than a brand-new lawn, since you're filling in an already established grass cover.
I have a bag of grass seed on hand — how large an area will it cover?
Use the "How large an area can I cover?" tab. Enter how many kg of seed you have and select the right seed rate — the calculator works out the largest area it will cover.