Free lawn seed calculator. Enter your lawn area in square metres to find the grass seed you need in grams and kilograms at 30 grams per square metre.
Your results will appear here.
Enter your values and press Calculate.
Enter your lawn area in square metres. This lawn seed calculator multiplies area by 30 grams per square metre, the middle of the cool season new lawn range, to give seed in grams and kilograms. A 100 square metre lawn needs 3000 grams, which is 3 kilograms. Check your seed packet for the exact rate for your grass type, and use about half the rate when overseeding.
Seed grams equal lawn area in square metres times 30. At 30 grams per square metre, 100 square metres need 3000 grams, which is 3 kilograms, and 50 square metres need 1500 grams, which is 1.5 kilograms. Competitor guides put the cool season new lawn range at 25 to 35 grams per square metre, so 30 grams sits in the middle and suits a first estimate. Always check the rate printed on your seed packet, because species and cultivars vary.
A new lawn needs a full rate, while overseeding an existing lawn needs roughly half that rate. Cool season grasses suit 25 to 35 grams per square metre for a new lawn and 12 to 18 grams for overseeding. Warm season grasses such as bermuda and zoysia suit 15 to 25 grams for a new lawn and 8 to 12 grams for overseeding. Using the new lawn rate on an existing lawn wastes seed and crowds seedlings, which invites disease.
Tall fescue suits 30 to 40 grams per square metre for a new lawn, perennial ryegrass suits 25 to 35 grams, and Kentucky bluegrass suits 15 to 20 grams. Ryegrass germinates fast and covers quickly, which suits high traffic areas, while bluegrass is slower but forms a dense turf. A seed mix blends these strengths, so use the rate for the mix on the packet rather than a single species rate.
A 1 kilogram bag of cool season seed covers about 33 square metres at 30 grams per square metre, or about 66 square metres when overseeding at 15 grams. A 20 kilogram bag covers roughly 660 square metres at the new lawn rate. In imperial units, 35 grams per square metre is about 7 pounds per 1000 square feet for a new lawn, and about half that for overseeding. Buy bags in whole sizes and round up, since seed is sold in fixed pack sizes.
Measure the lawn area as rectangles where you can, and split odd shapes into rectangles, circles or triangles and add them together. Subtract paths, beds and patios inside the boundary before you calculate, because seed spread over paving is seed wasted. For a circular lawn, area is pi times radius squared. Keep a small amount aside for patching thin spots after germination.
Split the seed in half and sow one half walking in one direction and the other half at right angles to it. This two directions method gives far more even coverage than a single pass and avoids bare stripes. Rake the seed lightly into the top few millimetres of soil, firm it gently, and water with a fine spray so the seed is not washed away. Never bury seed deeper than about 6 millimetres, because grass seed needs light to germinate.
Cool season grasses germinate in about 5 to 14 days, with ryegrass fastest and fescue slower. Warm season grasses take about 10 to 21 days, longer if soil temperatures stay below 18 degrees. Keep the seedbed moist for the first two to three weeks, watering lightly and often rather than flooding it. Wait until new grass reaches about 5 to 8 centimetres before the first mow, and take only the top off with sharp blades on a high setting.
Seed costs much less per square metre but takes 6 to 8 weeks to establish, and a full season before it takes heavy use. Turf costs considerably more but gives a usable lawn in 3 to 4 weeks, and suits slopes where seed washes downhill. Sow seed in early autumn or spring when the soil is warm and moist; autumn is often best because the ground stays warm, rain does the watering, and the lawn thickens all spring.
The common mistakes are using the new lawn rate when overseeding, forgetting to subtract paths and beds, sowing in one pass, skipping the waste allowance, and sowing in hot dry weather without irrigation. Add a waste allowance of 5 to 10 percent to cover edges, overlaps and birds, using the higher end when sowing by hand. Overcrowding from over sowing causes seedlings to compete and rot, so more seed is not always better.
For a new cool season lawn, sow 25 to 35 grams per square metre. This calculator uses 30 grams, the middle of that range. A 100 square metre lawn needs 3 kilograms.
No. Overseeding uses roughly half the new lawn rate: 12 to 18 grams per square metre for cool season grasses, because existing grass already covers most of the ground.
About 33 square metres at 30 grams per square metre for a new lawn, or about 66 square metres when overseeding at 15 grams per square metre.
Cool season grasses germinate in 5 to 14 days. Warm season grasses take 10 to 21 days, longer if the soil stays below 18 degrees. Keep the seedbed moist throughout.
Yes. Add 5 to 10 percent extra for edges, overlaps, birds and uneven spreading, and keep a little aside for patching thin spots after germination.
Seed is far cheaper but takes 6 to 8 weeks to establish. Turf costs more but is usable in 3 to 4 weeks, and suits slopes where seed washes away.
Early autumn or spring, when the soil is warm and moist. Autumn is often best: warm ground, natural rain, and a full spring to thicken.
Split it into rectangles, circles and triangles, work out each area, and add them together. Subtract paths, beds and patios inside the boundary first.
Find how many plants fit your garden bed, in square or triangular layouts, from bed size and plant spacing.
How much soil for a raised bed? Volume, bag counts, mix ratios, weight and cost in one tool.
Feed your lawn or garden the exact right amount