Find exactly how much grass seed your lawn needs. Enter the size in feet or metres, and get seed amounts in pounds and kilograms for a new lawn and for overseeding.
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Enter your values and press Calculate.
The calculator starts with the only two measurements that matter: length and width. It multiplies them to get the lawn area, converting metres to square feet first (1 sq m = 10.7639 sq ft) if you measured in metric. Next it applies the standard agronomic formula: divide the area by 1,000 and multiply by the seeding rate in pounds per 1,000 sq ft. It does this twice, once with your new-lawn rate (default 8) and once with your overseed rate (default 4), so a single input produces both quantities. Finally it converts each pound value to kilograms (1 lb = 0.453592 kg). All figures round to two decimals. The rates are adjustable because seed size varies so much between species: tall fescue and perennial ryegrass are seed-hungry (7 to 10 lb per 1,000 sq ft for new lawns), while Kentucky bluegrass and Bermuda are tiny-seeded (1 to 3 lb). Always prefer the rate printed on your seed bag over the defaults.
A lawn seed calculator tells you how much grass seed to buy for a given area. You enter your lawn's length and width (in feet or metres) plus the seeding rate for the job, and it returns the seed quantity in pounds and kilograms for both a brand-new lawn and for overseeding an existing one. The core rule is simple: divide your lawn area by 1,000 and multiply by the seeding rate, which is quoted in pounds per 1,000 square feet. Using a calculator instead of guessing avoids the two classic mistakes: buying too little, which leaves bare patches that invite weeds, and buying too much, which wastes money and makes seedlings compete with each other.
Enter your lawn's length and width, then pick the unit you measured in: feet or metres. If you already know the area, just type it as a length times width equivalent (for example, type 50 and 40 for a 2,000 sq ft lawn). Next, set the seeding rate for a new lawn (default 8 lb per 1,000 sq ft, adjustable between 6 and 10) and the overseeding rate (default 4 lb per 1,000 sq ft, adjustable between 3 and 5). Always check your seed bag first: species like Kentucky bluegrass and Bermuda need much lower rates, so dial the rate down to match the bag. The result instantly shows seed needed for a new lawn and for overseeding, in both pounds and kilograms, plus the computed lawn area in square feet.
The math behind the tool is the same agronomic formula every seed bag uses. First the area: area in square feet equals length times width, and if you measured in metres the calculator multiplies the result by 10.7639 (the number of square feet in one square metre). Then the two seed quantities: seed for a new lawn in pounds equals area divided by 1,000 times the new-lawn rate, and seed for overseeding in pounds equals area divided by 1,000 times the overseed rate. Each pound value is converted to kilograms by multiplying by 0.453592. No powers or complicated math: just area, one division, one multiplication, and a unit conversion.
New lawn seeding starts from bare soil, so every square foot needs full coverage and the seed rate is high: the calculator defaults to 8 lb per 1,000 sq ft with a 6 to 10 range. Overseeding spreads seed over existing turf to thicken thin or patchy areas, and because the old grass already covers most of the ground, it needs only about half the seed: the default is 4 lb per 1,000 sq ft with a 3 to 5 range. The single most common mistake is using the new-lawn rate when you only wanted to thicken a yard; that wastes seed and the crowded seedlings develop weak roots and fungal problems. If your job is somewhere between, such as heavy patch repair, pick a rate between the two.
Seeding rates are a property of the seed, not the yard, because seed size varies enormously. As a rough comparison across common species, using typical new-lawn figures per 1,000 sq ft: Kentucky bluegrass is tiny-seeded and frugal, around 2 to 3 lb new and 1 to 1.5 lb overseeding. Perennial ryegrass is seed-hungry, around 7 to 9 lb new and 3.5 to 4.5 lb overseeding. Tall fescue is the heaviest common cool-season grass at around 8 to 10 lb new and 4 to 5 lb overseeding, while fine fescue sits around 4 to 5 lb new and 2 to 2.5 lb overseeding. Bermuda, a warm-season grass, is tiny-seeded at around 1 to 2 lb new and 0.5 to 1 lb overseeding. Sun and shade mixes usually land near 6 lb new and 3 lb overseeding. These are industry averages; the rate printed on your bag always wins, and if it differs, enter that rate in the calculator instead.
Do not guess your square footage: walking it off is famously inaccurate. Start by dividing the lawn into rectangles, since most yards are not perfect squares. Measure the length and width of each rectangle in feet or metres, multiply to get each section's area, and add the sections together. Then subtract everything you will not seed: the driveway, patios, paths, deck footprint, and garden beds. For irregular edges, approximate with a rectangle that is a little generous, since seed is cheap and running short is the real problem. A free satellite measuring tool can trace your property lines for a fast, accurate reading without pacing the yard. Enter the total as length and width (or as area in the equivalent rectangle) and let the calculator do the rest.
Good application matters as much as good math. Split the seed in half and spread it in two passes at right angles, north-south then east-west, for even coverage; a broadcast spreader handles areas over 1,000 sq ft, while a drop spreader suits precise edges. Sow when soil is warm and moist: early fall for cool-season grasses and late spring for warm-season ones. Water immediately after seeding to activate germination, then keep the top inch of soil consistently moist with light watering two to three times daily until seeds sprout. Add five to ten percent extra seed for edges, overlaps, and birds, and keep a little aside for patching thin spots later. Wait until the grass reaches three to four inches before the first mow, and never cut more than a third of the blade height at once.
Take a 2,000 sq ft lawn seeded at the defaults. Area: 40 ft × 50 ft = 2,000 sq ft. New lawn: 2,000 / 1,000 × 8 = 16 lb of seed, which is 16 × 0.453592 = 7.26 kg. Overseeding: 2,000 / 1,000 × 4 = 8 lb of seed, which is 8 × 0.453592 = 3.63 kg. In metric terms, a 10 m × 10 m lawn is 100 sq m × 10.7639 = 1,076.39 sq ft, so a new lawn needs 1,076.39 / 1,000 × 8 = 8.61 lb (3.91 kg) and overseeding needs 4.31 lb (1.95 kg). For scale, one acre is 43,560 sq ft: at a typical 4 lb per 1,000 sq ft new-lawn rate that is about 174 lb for a new lawn or 87 lb for overseeding.
Coverage rate is the number of pounds of seed recommended per 1,000 square feet of lawn. Most turf grass seeding rate charts list two numbers: a new-lawn rate (full coverage on bare soil) and an overseeding rate (thinner, for patching existing turf). To calculate grass seed pounds for any lawn, measure your area, look up the seeding rate for your grass type on the chart, and multiply: (lawn area / 1000) × rate. A 5,000 sq ft lawn at a 6 lb per 1000 sq ft rate needs 30 pounds of seed.
The rate depends on the grass species, but for a new lawn most seed bags quote 5 to 10 lb per 1,000 sq ft, with 8 a common default for tall fescue and 6 for mixes. Seed-heavy species like tall fescue and perennial ryegrass sit at the top of the range, while tiny-seeded Kentucky bluegrass needs only 2 to 3 lb and Bermuda 1 to 2 lb. Check the bag and enter its rate in the calculator for an exact number.
Roughly half the new-lawn rate, because the existing turf already covers most of the ground. At typical rates that means about 2 to 5 lb per 1,000 sq ft depending on species: 4 to 5 lb for tall fescue, 1 to 1.5 lb for Kentucky bluegrass, 0.5 to 1 lb for Bermuda. Using the full new-lawn rate when overseeding wastes seed and causes overcrowding.
Between 5 and 10 lb per 1,000 sq ft for a new lawn is the normal planning range, with 8 lb a widely used default. For overseeding, expect 3 to 5 lb per 1,000 sq ft. The exact rate depends on the species: perennial ryegrass 7 to 9, tall fescue 8 to 10, Kentucky bluegrass 2 to 3, Bermuda 1 to 2, all in lb per 1,000 sq ft for new lawns.
In metric terms, a new cool-season lawn needs about 25 to 35 grams of seed per square metre, and overseeding about 12 to 18 grams. Warm-season grasses like Bermuda need less, around 15 to 25 grams per square metre for a new lawn. A 1 kg bag of cool-season seed at 30 g per square metre covers about 33 square metres for a new lawn, or about 66 when overseeding.
One acre is 43,560 square feet. At a typical new-lawn rate of 4 lb per 1,000 sq ft, a full acre needs about 174 lb of seed, or about 87 lb for overseeding. With tall fescue at 9 lb per 1,000 sq ft that climbs to nearly 400 lb per acre, while centipede grass at 0.5 to 1 lb per 1,000 sq ft needs only 30 to 40 lb per acre.
It depends entirely on the species and the bag size. A 50 lb bag of tall fescue covers roughly 5,500 sq ft for a new lawn, while 50 lb of Kentucky bluegrass covers up to 20,000 sq ft and Bermuda up to about 33,000 sq ft, because the seeds are much smaller and lighter. Divide bag weight by the seeding rate and multiply by 1,000 to get the covered area for any bag.
More seed does not grow a thicker lawn. Crowded seedlings compete for light, water, and nutrients, develop weak root systems, and are more prone to fungal disease. For overseeding this is the classic mistake: using the new-lawn rate on existing turf causes severe overcrowding. Measure, use the right rate, and add only a small 5 to 10 percent allowance for waste.
Yes, blending compatible species is common and often recommended. A popular mix is Kentucky bluegrass with perennial ryegrass: the ryegrass germinates in 5 to 7 days for quick cover while the slower bluegrass fills in over time. Stick to grasses of the same season type, cool-season with cool-season or warm-season with warm-season, and use the rate on the mix packaging.
For cool-season grasses like fescue, bluegrass, and ryegrass, early fall is best, with early spring as the second choice. For warm-season grasses like Bermuda and zoysia, seed in late spring to early summer when soil temperatures are consistently warm. Seed needs consistent moisture to germinate, so avoid hot, dry stretches without irrigation.
It varies by species. Perennial ryegrass is fastest at 5 to 10 days. Tall fescue and fine fescue take 7 to 14 days. Kentucky bluegrass is slowest among cool-season grasses at 14 to 30 days. Warm-season grasses like Bermuda need warm soil and take 10 to 30 days. Keep the seedbed consistently moist the whole time.
Most turf types need 4 to 8 pounds of grass seed per 1000 sq ft for a new lawn, and 2 to 4 pounds per 1000 sq ft for overseeding. Tall fescue runs around 6 to 8 lb, Kentucky bluegrass 2 to 3 lb, and perennial ryegrass 8 to 10 lb. Always check the seeding rate chart on the seed bag, since coated seed weighs more per bag but covers less area.
Every reputable seed bag prints a seeding rate chart on the label, and extension services publish tables per grass species. The rate chart lists pounds per 1000 sq ft for new lawns and for overseeding, so match the row to your grass type and multiply by your lawn area.
For non-rectangular lawns, break the shape into rectangles and triangles: area = (length × width) for each rectangle plus (base × height / 2) for each triangle, then add them up. For a circle, use 3.14 × radius × radius. Overlap the pieces generously so you buy enough seed; the calculator above handles rectangular areas, so compute odd shapes by section and enter the total.
Throwing down grass seed without soil contact gives patchy results. Seed needs firm contact with soil to germinate, so rake the area, spread the seed evenly, press it in with a roller or your feet, then keep it moist. Broadcasting seed over dense thatch or dead grass usually fails.
Yes, water immediately after putting grass seed down, gently, so the soil is moist but not washed away. Keep the top inch of soil damp with light daily watering until germination (usually 7 to 21 days), then water less often but deeper as the seedlings root.
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