Work out how much grass seed you need for a new lawn or overseeding based on lawn area and sowing rate.
Enter the length and width of your lawn, and choose whether you are sowing a new lawn or overseeding an existing one — this sets a typical sowing rate. Adjust the rate if your seed bag recommends a different figure. The tool returns the weight of seed to buy.
| Job | Rate |
|---|---|
| New lawn | 35 g/m² (≈ 1 lb per 40 ft²) |
| Overseeding | 25 g/m² |
| Hard-wearing / sport mix | 40–50 g/m² |
A new lawn 10 m × 8 m = 80 m². At 35 g/m² that is 80 × 35 = 2,800 g ≈ 2.8 kg of seed. For overseeding the same lawn you would need about 2 kg.
Tip: sow in spring or early autumn when the soil is warm and moist, and keep the surface damp until the seedlings are well established.
For a brand new lawn allow roughly 35 grams per square metre. For overseeding a thin lawn, around 20 grams per square metre is usually enough.
Early autumn and mid spring are ideal, when the soil is warm and moist but not baked or frozen.
It is worth buying a little extra to patch any thin areas a few weeks after sowing.
Most lawn seed germinates in 7–21 days depending on temperature and moisture. Ryegrass is quickest; fescues and bents are slower. Keep the soil consistently damp until the seedlings establish.
Lightly rake the seed in, and on bare soil a thin layer of topsoil or seed compost helps retain moisture and protect it from birds. Avoid burying it deeper than about 5–10 mm.
