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Grass Seed Calculator

Find how much grass seed you need.

How it is calculated

The tool multiplies the lawn area by the seeding rate: seed (g) = area (m²) × rate (g/m²), then converts to kilograms by dividing by 1,000. If the rate is left empty or is not positive, it falls back to 35 g/m², a typical figure for general lawn mixes. The kilogram result has two decimals and the gram result is rounded to a whole gram. Check the packet: overseeding, shade mixes and repair patches use different rates, and new lawns often need more than renovation. Area is not corrected for slopes or for beds and paths, so subtract bare areas yourself.

Worked example

A lawn of 200 m² with a sowing rate of 35 g/m². Seed = 200 × 35 = 7,000 g. Converted to kilograms: 7,000 / 1,000 = 7.00 kg. The tool therefore shows 7.00 kg, or 7,000 g. If the seed is sold in 5 kg bags, you need two bags, with a little left for patching.

Try this example →

Common mistakes

  • Entering the area in square feet or the rate in pounds per 1,000 sq ft; this tool uses m² and g/m².
  • Forgetting that the default 35 g/m² is used when the rate is blank, and not checking the packet.
  • Measuring the whole plot and not subtracting paths, flower beds or buildings.
  • Confusing grams with kilograms when buying: 7,000 g is 7 kg.

About this calculator

This calculator multiplies a lawn's area by a seeding rate — the pounds of seed recommended per 1,000 square feet, which varies by grass species and whether you're seeding bare soil or overseeding an existing lawn — to tell you how much seed to buy.

Landscapers and lawn-care professionals use it to quote and order the right amount of material, and homeowners use it to avoid under-seeding (leaving thin patches) or over-seeding (wasting seed and money) a new or repaired lawn.

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  • Editorial team

    For a 120 m² lawn the default 35 g/m² rate gives 4.20 kg. Break an irregular lawn into rectangles and triangles, add their areas, then subtract beds and paths before entering the total. When sowing, split the seed in two and spread one half in each direction, crossways, to avoid stripes. Packet rates differ by mix, so enter the figure from your own bag. What kind of lawn are you sowing, a new one or a repair?

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