Grass Seed Calculator
The pounds of seed your lawn actually needs — and the bag to buy.
Your lawn
Materials list
Generated by AllUnits.io — allunits.io/calculators/grass-seed
How this calculator figures it
Seeding rates follow university turf-program guidance (Michigan State and Cornell extension): 8–10 lb per 1,000 sq ft for tall fescue, 2–3 lb for Kentucky bluegrass, 7–8 lb for perennial ryegrass, with overseeding at roughly half rate. Rates differ by species because seed size differs — a pound of bluegrass holds about ten times as many seeds as a pound of fescue.
How it works
Each grass type has a published rate range per 1,000 square feet, so the answer is always a range too. The buy line rounds the high end up to the next common bag size (3, 7, 10, 20, or 50 lb) so one purchase covers the job. Overseeding uses half the new-lawn rate. Worked example — 2,000 sq ft of tall fescue as a new lawn: 2,000 ÷ 1,000 × 8–10 = 16–20 lb; buy a 20 lb bag.
Grass seed FAQs
When is the best time to seed?
For cool-season grasses, late August through September — the soil is warm and weeds are fading. Spring is second best. Per MSU Extension guidance.
Why does Kentucky bluegrass need so little seed?
Tiny seeds — around 1 to 2 million per pound — so 2–3 lb per 1,000 sq ft is the full rate.
How much seed for overseeding?
About half the new-lawn rate.
Does extra seed grow a thicker lawn?
No — overcrowded seedlings compete and damp off. Stay in the recommended range.
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Related calculators & sources
Instant lawn instead of seed: Sod Calculator. Soil prep first: Topsoil Calculator. Seeding rates come from MSU and Cornell turf-program guidance; convert measurements with the area and weight converters.
Estimates for planning and purchasing. Not engineering or code-compliance advice — confirm structural work with your local building department.