Grass Seed Calculator
How much grass seed do I need?
The standard UK sowing rate is about 35 grams per square metre for a brand new lawn and around 25 grams per square metre when overseeding to thicken an existing one. Pick the job and enter your area, and the calculator gives the weight of seed in kilograms.
Sow at the right density: too little and the lawn comes through patchy and weak, too much and the seedlings compete and thin out. Spring and early autumn are the best times, on raked, firmed soil that is kept damp until the grass establishes.
Frequently asked questions
Is the grass seed calculator free?
Yes. It is completely free, with no sign-up and nothing to install. It runs entirely in your browser.
How accurate is it?
It gives a reliable estimate for ordering based on standard UK figures, but real quantities vary with ground conditions, wastage and how materials settle. Always add a margin and confirm with your supplier before buying.