Formula
- Lawn area = length × width.
- Seed = lawn area × sowing rate × (1 + allowance ÷ 100), rounded up to the next gram.
Assumptions and limits
- Follow the selected seed product's rate for new lawns or overseeding.
Garden calculator
Lawn Seed Calculator
Estimate grass seed from lawn area and the packet sowing rate.
Example with the pre-filled values
Lawn area (m²): 60 · Seed needed (g): 2205 · Seed needed (kg): 2.21
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Worked example
A 10 × 6 m lawn is 60 m². At 35 g per m² with a 5% allowance you need 60 × 35 × 1.05 = 2,205 g, about 2.2 kg of seed.
| Input | Value |
|---|---|
| Lawn length | 10 m |
| Lawn width | 6 m |
| Sowing rate | 35 g/m² |
| Extra allowance | 5 % |
| Result | Value |
|---|---|
| Lawn area (m²) | 60 |
| Seed needed (g) | 2,205 |
| Seed needed (kg) | 2.21 |
Reading the result
- Use the sowing rate printed on your seed packet; it varies between mixes and between new lawns and overseeding.
- The RHS notes that sowing more heavily is one way to compensate for birds if the seed is not covered.
- Sow in suitable conditions (typically early autumn or mid-spring in the UK) and keep the seedbed moist.
Sources and further reading
- RHS: starting a lawn from seed — Use the weight per square metre printed on the seed packet.