Lawn Seed Calculator
The Lawn Seed Calculator estimates how much grass seed to buy based on your lawn area and seeding rate, whether you're overseeding an existing lawn or starting fresh. Works in U.S. or metric units. Because lawns are purchased by weight rather than exact area, the calculator scales your seeding rate to your precise lawn size instead of rounding to a fixed bag size — helping you buy close to what you'll actually use. The seeding rate itself is the biggest variable: grass species, whether you're overseeding or starting from bare soil, and your region's climate all shift the recommended rate, so check your seed product's label alongside the general guidance below.
Switch between U.S. Customary and Metric units.
How This Tool Works
Pick your units, then enter your lawn's length and width, and choose a seeding rate — lighter for overseeding an existing lawn, heavier for starting from bare soil.
Formula & Method
Seed needed = area × seeding rate. In U.S. units, rate is pounds per 1,000 sq ft (result in lbs); in metric, grams per square meter (result in kg).
Example Calculation
A 3,500 sq ft lawn being overseeded at a light 3.5 lbs per 1,000 sq ft needs 12.25 lbs of seed (3.5 × 3,500 ÷ 1,000). If that same lawn were started from bare soil at a heavier 8 lbs per 1,000 sq ft, it would need 28 lbs (8 × 3,500 ÷ 1,000). In metric, a 325 m² lawn seeded new at 35 g/m² needs about 11.38 kg of seed.
Frequently Asked Questions
How much seed do I need per 1,000 sq ft?+
Overseeding an existing lawn typically needs 3–4 lbs per 1,000 sq ft (about 15–20 g/m²), while a brand-new lawn from bare soil needs 6–8 lbs per 1,000 sq ft (30–40 g/m²).
Can I calculate grass seed in kg and grams per square meter?+
Yes — switch the unit toggle to Metric and enter your lawn in meters with the seeding rate in grams per square meter. The result is returned in kilograms.
When is the best time to seed a lawn?+
Early fall is generally best for cool-season grasses, while late spring works well for warm-season grasses — check what's recommended for your grass type and region.
Should I fertilize when seeding?+
A starter fertilizer applied at seeding often helps new grass establish faster, but follow product-specific application rates rather than your regular lawn fertilizer schedule.
What if my grass seed product recommends a rate outside the typical range?+
The field accepts 1–20 lbs/1,000 sq ft (5–100 g/m² in metric), but most rates fall between roughly 3–8 lbs/1,000 sq ft. Different grass types vary — fine fescue and Kentucky bluegrass, for example, call for different rates — so follow your specific product's label over a general rule of thumb.
Should I buy exactly the calculated amount of seed?+
Round up slightly. Seed bags come in fixed sizes (commonly 3, 7, 20, or 50 lb bags), so it's better to have a little extra on hand for touch-up spots or reseeding thin areas than to run short partway through the job.
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<a href="https://everyfix.net/tools/lawn-seed-calculator/">Lawn Seed Calculator</a> by <a href="https://everyfix.net">EveryFix</a>Related Tools
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