Lawn Seed Quantity Calculator NZ
This calculator works out how much grass seed you need to sow a lawn in New Zealand, from the area you are covering and the sowing rate, so you buy the right amount rather than guessing at the garden centre. Sowing too little seed gives a thin, patchy lawn that lets weeds in, while sowing far too much wastes money and can cause the seedlings to compete and grow weakly, so matching the quantity to the area and the job pays off. The calculation is simple: multiply the lawn area in square metres by the sowing rate in grams per square metre, then convert to kilograms. The right rate depends on the job. A bare new lawn needs the full rate, commonly thirty-five to fifty grams per square metre, to establish dense coverage, while over-sowing to thicken an existing lawn uses a lighter rate of around fifteen to twenty-five grams. You enter your lawn length and width, and the sowing rate, and the calculator returns the area and the seed required in grams and kilograms. For the best results in New Zealand, sow in spring or early autumn when the soil is warm and moisture is reliable, prepare the ground well, and keep it watered until the seed germinates. An estimate to plan your lawn.
Use about 35 to 50 g/m² for a new lawn and 15 to 25 g/m² for over-sowing. Sow in spring or early autumn. An estimate for planning only.
How it works
The lawn area is the length times the width. The seed needed in grams is the area times the sowing rate, and dividing by 1,000 gives the kilograms to buy. Choose a higher rate for a new lawn and a lower rate for over-sowing.
Worked example
A 10 by 8 metre lawn is 80 square metres. At a new-lawn rate of 35 grams per square metre, that is 2,800 grams, or about 2.8 kilograms of grass seed.
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