Grass Seed Calculator

Grass Seed Calculator Tool

Lawn and seed details

Length (ft)

Width (ft)

Or area directly (sq ft)

Grass species

Seeding type

Seed bag size (lbs)

Price per bag ($ optional)

Reset

St. Augustinegrass is propagated by sod or plugs, not seed. Note shown if selected.

Enter values and click Calculate

Grass seed needed

Seed rate used

lbs per 1,000 sq ft

Bags needed

at selected bag size

Cost estimate

at entered price per bag

Area covered

sq ft

Why use this free grass seed calculator?

Built with the features most competitors miss — deeper inputs, benchmark data, and actionable guidance alongside the core calculation.

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14 grass species with rates

Pre-loaded seeding rates for cool-season and warm-season species covering North America.

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New seeding and overseeding rates

Separate rates for bare-ground installation and overseeding of existing turf.

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Bag count and cost estimate

Calculates bags needed for 3, 5, 10, 25, and 50 lb bags plus total cost.

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Length/width or sq ft input

Flexible area entry for any lawn shape.

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Plug/sod note for St. Augustine

Flags species not available as seed with appropriate alternative guidance.

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Free, browser-based

No registration, no download. Works on any device.

How to use this grass seed calculator

Enter lawn dimensions or area

Enter length and width in feet, or total area directly in sq ft.

Select grass species

Choose your species. The recommended seeding rate is applied automatically.

Select new seeding or overseeding

New seeding uses full rate; overseeding uses a reduced rate over existing turf.

Select bag size and add price

Match to the bags at your garden centre. Add price for a total cost estimate.

Grass seed rates by species

Species	New seeding (lbs/1k sqft)	Overseed (lbs/1k sqft)	Climate
Kentucky Bluegrass	2 to 3	1 to 2	Cool-season
Tall Turf-Type Fescue	6 to 8	4 to 5	Cool-season (shade-tolerant)
Perennial Ryegrass	8 to 10	4 to 6	Cool-season (fast)
Bermudagrass (hulled)	1 to 2	0.5 to 1	Warm-season
Zoysiagrass	1 to 2	0.5 to 1	Warm-season
Tall Fescue	6 to 8	3 to 4	Cool-season

How this calculator compares

LazyTools fills the gaps most competing tools leave open — deeper analysis, benchmark context, and actionable guidance alongside the core calculation.

Feature	LazyTools	OmniCalculator	Pennington.com	Scotts.com
14 grass species	✓ Yes	Partial	Partial	Partial
New vs overseeding rate	✓ Yes	✓	✓	✓
Bag count and cost	✓ Yes	✓	✓	✓
Area in sq ft or dimensions	✓ Yes	✓	✓	✗
Germination time guide	✓ Yes	✗	✗	Partial
Free, no registration	✓ Yes	✓	✓	✓

📖 Complete guide

Grass Seed Calculator: Complete Guide

Buying the right amount of grass seed is straightforward with this calculator — enter your lawn size and species and get the exact pounds needed for new seeding or overseeding, along with bag count and cost estimate.

Why seeding rates differ between species

Grass seed size varies enormously between species. Kentucky Bluegrass has approximately 2.2 million seeds per pound, requiring a low application rate because each pound contains millions of individual seeds. Perennial Ryegrass has approximately 230,000 seeds per pound, so a much higher rate by weight is needed to achieve the same plant density. Bermudagrass at approximately 1.8 million seeds per pound uses low rates similar to KBG.

New seeding vs overseeding rates

New seeding (bare soil) uses the full recommended rate to establish a dense stand from nothing. Overseeding (over existing thin or damaged turf) uses 40 to 60% of the new seeding rate because existing grass fills in gaps over time, providing additional competition that reduces the percentage of new seeds needed. Applying full new-seeding rates over existing turf wastes seed money.

Seed bed preparation for success

Soil-to-seed contact is the most important factor in germination. For new seedings: till the top 2 to 4 inches, remove debris, and lightly rake before seeding. For overseeding: core aerate before seeding to create holes for seed-to-soil contact. After seeding, a light drag or roller improves contact. Apply a starter fertiliser (18-24-12 or similar) at seeding for best early establishment.

Watering a newly seeded lawn

Keep the seed bed consistently moist (but not waterlogged) until germination: typically 2 to 3 light waterings per day for the first 2 to 3 weeks. After germination, reduce frequency but increase depth to encourage deep rooting. Inconsistent moisture is the leading cause of poor germination in new lawn seedings.

Frequently asked questions

How much grass seed do I need per square foot?

Seeding rates are measured per 1,000 sq ft. Kentucky Bluegrass new seeding: 2 to 3 lbs/1,000 sq ft. Tall fescue: 6 to 8 lbs. Perennial ryegrass: 8 to 10 lbs. Total seed needed = (Area / 1,000) x Rate.

What grass seed rate should I use for overseeding?

Overseeding rates are 40 to 60% of new seeding rates because existing grass provides some competition. KBG overseed: 1 to 2 lbs/1,000 sq ft. Tall fescue overseed: 4 to 5 lbs. Perennial ryegrass overseed: 4 to 6 lbs.

What is the best grass seed for a new lawn?

Depends on climate: Cool-season (northern US, Canada): Kentucky Bluegrass (premium), Tall Turf-Type Fescue (low maintenance), Perennial Ryegrass (fast establishment). Warm-season (southern US): Bermudagrass (heat/drought), Zoysiagrass (shade tolerance), Bahiagrass (low maintenance).

How do I calculate grass seed for an irregular yard?

Break the yard into simple shapes (rectangles, triangles), calculate each area, and sum them. Or measure total sq ft by pacing the perimeter and estimating average width. Enter total sq ft directly in the calculator.

When is the best time to seed a lawn?

Cool-season grasses: late summer to early autumn (August to September in zones 4 to 7) when soil is warm and air is cooling. Spring seeding is second best. Warm-season grasses: late spring to early summer when soil temperatures reach 65 to 70F consistently.

How deep should grass seed be planted?

Grass seed germinates best at 1/8 to 1/4 inch depth. Most seed is simply raked in or covered with a thin layer of topsoil or seed accelerant. Do not plant deeper than 1/4 inch or germination rate drops dramatically.

How much does grass seed cost for a typical yard?

A 5,000 sq ft lawn at perennial ryegrass rates (9 lbs/1,000 = 45 lbs total): at $3 to $5/lb for quality seed = $135 to $225. KBG (2.5 lbs/1,000 = 12.5 lbs): at $5 to $8/lb = $62 to $100. Premium seed costs more but often has higher germination rates and disease resistance.

What is the germination time for common grass seeds?

Perennial ryegrass: 5 to 10 days (fastest). Tall fescue: 7 to 12 days. Kentucky Bluegrass: 14 to 30 days (slowest; be patient). Bermudagrass: 10 to 30 days. Zoysiagrass: 14 to 21 days.

How many pounds of grass seed per acre?

Multiply per-1,000 sq ft rate by 43.56. Tall fescue (7 lbs/1,000): 305 lbs/acre. KBG (2.5 lbs/1,000): 109 lbs/acre. Perennial ryegrass (9 lbs/1,000): 392 lbs/acre.