Grass Seed Calculator

Grass seed is sold by weight, and the quantity you need depends on whether you are starting a lawn from bare soil or thickening an existing one. A new lawn needs considerably more seed than overseeding, because every square foot must be colonised from scratch, while overseeding only fills gaps between established plants that are already doing most of the work. The standard rates are a useful guide. Roughly four pounds per thousand square feet suits a new lawn with good soil and careful watering; overseeding calls for about half that, and repairing bare patches needs a heavier rate to give the new grass a chance against competition. These figures assume decent seed and good conditions — thin soil, shade or a poor seedbed may need more, and buying cheap seed with low germination simply multiplies the quantity you need. Timing and contact with soil decide success more than quantity. Seed scattered on a hard, bare surface is food for birds; the same seed raked into the top quarter-inch and kept damp will germinate. Consistent moisture for the first two or three weeks matters more than any other single factor, and a seed-to-soil contact using a light raking, rolling or a dedicated overseeder transforms the results. This calculator applies the rate for your type of job to your measured area and rounds up to a purchase quantity. It assumes an even spread and average conditions, and it does not account for slope or heavy shade, both of which warrant extra seed. Divide the lawn into manageable sections and weigh out the seed for each, so no area is over- or under-sown.

This calculator returns estimates for planning and general information only. It is not engineering, architectural, structural, electrical or code advice, and it cannot replace a qualified professional who has seen the site. Material quantities depend on the actual dimensions, the product you buy and local building codes, so confirm the figures before ordering materials or starting work, and always follow local regulations.