About this calculator
How much grass seed to buy for a new lawn or overseeding, using typical sowing rates for each seed type.
How it’s calculated
Seed (kg) = area × rate (g/m²) ÷ 1,000. New lawns usually take 35–50 g/m² and overseeding 15–25 g/m².
Worked example
With these inputs:
- Area shape
- Rectangle
- Length
- 10 m
- Width
- 8 m
- Job
- New lawn
- Seed type
- Hard-wearing (rye mix)
the result is:
- Seed needed
- 2.8 kg
Tips from the trade
- Split the seed in half and sow in two directions for even cover.
- Keep the seedbed moist (not soaked) until the grass is established.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and the Building Regulations before ordering.