OpenTools

Construction & Home Improvement

Grass Seed Calculator

Estimate how much grass seed you need for a new lawn: seed in lbs, whole bags, and a cost range by grass type.

Grass seed estimate

Enter the lawn size and grass type for a new lawn. The tool finds seed lbs, bags, and a cost range.

Bag size and price

How this estimate works

Seed needed is seed (lbs) = area ÷ 1,000 × new-lawn rate × (1 + waste%). The rate comes from the grass type you select and assumes a new lawn on prepared soil.

Bags are bags = ⌈ seed lbs ÷ bag size ⌉, rounded up.

Cost is cost = seed lbs × $/lb, using per-pound retail prices that vary by grass type.

For example, a 1,000 sq ft new lawn with tall fescue (8 lbs/1,000 sq ft) and a 10% allowance needs about 8.8 lbs — two 5 lb bags, roughly an $18–$53 range.

Before you seed

Always check your seed bag's stated coverage — rates differ by cultivar, blend, and germination conditions. The calculator's rates are midpoints of published ranges.

Prepare the soil (till, level, remove debris), spread seed evenly with a spreader, rake lightly, and water frequently until the new grass is established.

Grass seed calculator FAQ

How much grass seed do I need for a new lawn?
It depends on the grass type and lawn size. Typical new-lawn rates are 2–4 lbs per 1,000 sq ft for Kentucky bluegrass, 6–10 lbs for tall fescue, 5–10 lbs for perennial ryegrass, and about 5 lbs for fine fescue.
What's the difference between seeding a new lawn and overseeding?
A new lawn needs roughly twice the seed because you are starting from bare soil. Overseeding thickens existing grass at a lower rate — use the Overseeding Calculator for that job.
When is the best time to plant grass seed?
For cool-season grasses (bluegrass, fescue, ryegrass), early fall or early spring is ideal — soil temperatures support germination and there is less weed competition.
How deep should grass seed be planted?
Grass seed should be about 1/4 to 1/2 inch deep. Rake the soil lightly after spreading, roll or tamp for seed-to-soil contact, and keep it moist until germination.

Method & sources

Seed lbs, bag count, and cost are computed at full precision and rounded only for display. Bag count is rounded up because seed is sold in whole bags.

Important limits

  • Uses published new-lawn rates by grass type — always confirm against your seed bag label.
  • Estimates one rectangular lawn from dimensions or a known area; does not model irregular shapes or slopes.
  • Cost is a planning range from 2026 US retail prices; delivery, soil prep, and labour are not included.

Reviewed references