Gardening
Lawn Seed Calculator
Enter lawn area and grams per square metre to see seed needed with a waste buffer.
How much grass seed?
Grass seed need is lawn area × sowing rate in grams per square metre, then a buffer for birds, wind and imperfect spreading. New lawns usually need a higher rate than overseeding thin turf — always prefer the grams-per-square-metre figure on your seed box, because shade, ryegrass and sports mixes differ. Enter area, rate, extra buffer percent and optional price per kilogram to see grams, kilograms and spend. Good soil prep and watering matter as much as the gram count. For bed planting density elsewhere in the garden see plant spacing; for measuring awkward lawn shapes first use garden area.
Worked example
80 m² at 35 g/m² = 2,800 g (2.8 kg) before buffer. With 10% extra ≈ 3,080 g (3.08 kg); at £12/kg ≈ £36.96.
Limits and assumptions
Follow the supplier sowing rate for your mix. Germination depends on season, moisture and prep — not modelled here.
Frequently asked questions
Overseeding vs a new lawn — which rate?
Overseeding packs quote a lower rate than full new-lawn rates. Use the figure printed for the job you are doing.
When is the best time to sow?
Depends on climate; many temperate lawns prefer moist, mild seasons. The calculator only handles quantity.
My lawn is measured in square feet — can I still use this?
Yes — switch the site area units so area matches your measurement, and keep the sowing rate consistent with the label.
What about wildflower seed mixes?
Enter the rate printed for that mix; do not assume a standard lawn rate.