Calculators · Grass Seed Calculator

Landscaping

Grass Seed Calculator

Enter your lawn area and pick a grass to get the pounds of seed and bags to buy, for a new lawn or overseeding.

Area 1

Shape

Length

Width

Counts as

Grass type and job

New lawn or overseeding. Choose “Custom rate” to use your own.

Seeding rate (lb per 1,000 sq ft)

Type the rate from your seed bag.

Pure seed on the tag (%)

Optional. Type it with the germination to adjust for pure live seed.

Germination on the tag (%)

Optional. Leave both empty to skip the adjustment.

Bag size (lb)

Optional. Gives the number of bags and what one bag covers.

How to calculate how much grass seed you need

Seeding rates are written per 1,000 square feet, so the job is to find the lawn area, divide it by 1,000 and multiply by the rate. Measure each part of the lawn and subtract what you will not seed. The calculator also adds up rectangles, circles and triangles for you, or takes an area you already know.

Step	Formula
1. Lawn area	area to seed (sq ft) = lawn areas − patios, beds and buildings
2. Seed at the rate	pounds = area ÷ 1,000 × rate in lb per 1,000 sq ft
3. Adjust for the tag	only if the tag is below the minimum the rate assumes (see below)
4. Bags	bags = pounds to buy ÷ bag weight, rounded up

Grass seed rates by type

These are the rates the calculator uses. They come from university extension services and were checked in October 2026. The new lawn rates for cool-season grasses are from Penn State Extension. Bermudagrass is from the NC State Extension Gardener Handbook. The overseeding rates are from University of Nebraska-Lincoln. The last column shows what other extension services give, because they do not all agree.

Grass and job	lb per 1,000 sq ft	Other extension figures
Kentucky bluegrass, new lawn	2 to 3	Ohio State 2 to 3, Kentucky 2 (pure live seed), NC State 1 to 2
Turf-type tall fescue, new lawn	6 to 8	Ohio State 8 to 10, Kentucky 6, NC State 6
Turf-type perennial ryegrass, new lawn	4 to 5	Ohio State 7 to 8, Kentucky 4 to 6 (pure live seed, broadcast)
Fine fescues, new lawn	4 to 5	Ohio State 3 to 6
Bermudagrass (seeded), new lawn	1 to 2	Kentucky 1 to 2 (pure live seed). NC State says coated seed may need double
Kentucky bluegrass, overseeding	about 2	Nebraska only
Tall fescue, overseeding	3 to 4	Nebraska only

The dropdown fills the box with the midpoint of the range. The midpoint is our own arithmetic, not a figure from the source. The result also shows the pounds across the whole range so you can see the spread. Other sources are Ohio State and University of Kentucky publication AGR-52 (checked October 2026).

Example: a lawn with a patio

A lawn measures 100 ft by 60 ft and has a 20 ft by 15 ft patio in it. You are seeding a new turf-type tall fescue lawn at 7 pounds per 1,000 square feet, the midpoint of 6 to 8. The tag says 98% pure seed and 85% germination, and the bag is 50 pounds.

Step	Operation	Result
Lawn area	100 × 60 − 20 × 15	5,700 sq ft
Seed at the rate	5,700 ÷ 1,000 × 7	39.9 lb
Pure live seed on the tag	98 × 85 ÷ 100	83.3%
Penn State minimum for tall fescue	95 × 80 ÷ 100	76%
Pounds to buy	83.3% is above 76%, so no adjustment	39.9 lb
Bags of 50 lb	39.9 ÷ 50 = 0.80, rounded up	1 bag

Across the whole 6 to 8 pound range the same lawn needs between 34.2 and 45.6 pounds of seed, which is why the result shows the range next to the single figure. If the tag showed 80% pure seed and 85% germination instead, the PLS would be 68%, below the 76% the rate assumes. Then 39.9 × 76 ÷ 68 = 44.59 pounds, still one 50 pound bag.

Pure live seed explained

Penn State Extension explains that some seed is sold with low purity or low germination, and that the rate should be raised to make up for it. To find the percent pure live seed, multiply the percent pure seed by the percent germination and divide by 100. Its own example is 85% pure seed and 72% germination, which is about 61% PLS. Dividing 100 by that gives 1.6, so you need about 1.6 pounds of that seed for every pound specified. Penn State also says its rates are based on the minimum purity and germination in its Table 1: Kentucky bluegrass 90% and 80%, perennial ryegrass 95% and 85%, tall fescue 95% and 80%, fine fescues 95% and 80%. That is 72%, 80.75%, 76% and 76% PLS. So for the Penn State grasses the calculator only adds seed when your tag falls below that minimum, because the rate already counts it. For the other rates, which do not state a purity or germination, and for a rate you type yourself, it divides by the full PLS. If your own rate already counts the tag, leave the two boxes empty. With both boxes empty, the calculator does not adjust anything.

How much will a bag cover?

The area one bag covers is the bag weight divided by the rate, times 1,000. Add the PLS adjustment first if your tag shows low purity or germination.

Rate (lb per 1,000 sq ft)	One 20 lb bag covers	One 50 lb bag covers
2	10,000 sq ft	25,000 sq ft
2.5	8,000 sq ft	20,000 sq ft
3.5	5,714 sq ft	14,286 sq ft
4.5	4,444 sq ft	11,111 sq ft
7	2,857 sq ft	7,143 sq ft

Pounds of seed for common lawn sizes

Lawn size	Kentucky bluegrass, new (2.5)	Perennial ryegrass, new (4.5)	Tall fescue, new (7)	Tall fescue, overseeding (3.5)
1,000 sq ft	2.5 lb	4.5 lb	7 lb	3.5 lb
2,500 sq ft	6.25 lb	11.25 lb	17.5 lb	8.75 lb
5,000 sq ft	12.5 lb	22.5 lb	35 lb	17.5 lb
10,000 sq ft	25 lb	45 lb	70 lb	35 lb

New lawn or overseeding?

Overseeding thickens a lawn that is already growing, so the rate is lower than for bare soil. Nebraska Extension gives around 2 pounds of Kentucky bluegrass per 1,000 square feet for overseeding, against 1 to 3 for a new lawn, and 3 to 4 pounds of tall fescue, against 5 to 8 for a new lawn. If you would rather lay turf, the sod calculator counts rolls and pallets. To work out how much fertilizer your lawn needs, use the lawn fertilizer calculator.

Tips for ordering

Read the seed tag. The pure seed and germination percentages decide how much you really need.
Use the rate printed on the bag when it differs from the table. The bag knows its own cultivar and coating.
Subtract areas you will not seed with “Not lawn (subtract)”, such as the house footprint, a patio or a bed.
Spread the seed in more than one direction, as Nebraska Extension suggests, so the coverage is even.
Prices change by seed, region and supplier, so this calculator shows none. Ask for the price per pound or per bag.

Frequently asked questions

How do you calculate how much grass seed you need?

Find the lawn area in square feet, divide it by 1,000, and multiply by the seeding rate in pounds per 1,000 square feet. A 5,000 square foot lawn at 7 pounds per 1,000 needs 5 × 7 = 35 pounds. Subtract patios, beds and the house footprint first, since you do not seed them.

How much will a 50 lb bag of grass seed cover?

Divide 50 by the seeding rate and multiply by 1,000. At 2 pounds per 1,000 square feet a 50 pound bag covers 25,000 square feet, at 4.5 it covers 11,111 and at 7 it covers 7,143. The calculator does this when you type the bag weight, even if you leave the lawn size empty.

Can you just throw grass seed and it will grow?

Seed needs the right conditions to establish. For overseeding, University of Nebraska-Lincoln Extension says air temperatures should be around 60 to 75°F for cool-season grasses, that aerifying first can help seed establishment, that you should spread the seed in different directions, and that you should water right after seeding. It says to water sparingly up to three times a day in the first week. Too much water can lead to disease or loss of seed.

How many pounds of grass seed per 1,000 square feet for overseeding?

University of Nebraska-Lincoln Extension gives around 2 pounds of Kentucky bluegrass and 3 to 4 pounds of tall fescue per 1,000 square feet, which is less than for a new lawn. We found no overseeding figure from a university for the other grasses, so the calculator asks you to type the rate from your seed bag for those.

How many pounds of grass seed per acre?

An acre is 43,560 square feet, so multiply the rate per 1,000 square feet by 43.56. Two pounds per 1,000 square feet is 87.12 pounds per acre and 7 pounds per 1,000 is 304.92 pounds per acre.

Why do extension services give different seeding rates?

Rates depend on the species, the cultivar, whether the seed is coated and the region. For tall fescue we found 6 pounds per 1,000 square feet in University of Kentucky publication AGR-52 and at NC State, 6 to 8 at Penn State and 8 to 10 at Ohio State. Use the figure from your own state or the seed bag, and type it in the rate box.

What is pure live seed and why does it matter?

Pure live seed (PLS) is the share of the bag that is real seed that can germinate. Penn State Extension multiplies the purity percentage by the germination percentage and divides by 100. Purity 98% and germination 85% give 83.3% PLS. Penn State says its rates already assume minimum purity and germination, which is 95% and 80% for tall fescue, or 76% PLS. A tag of 83.3% meets that, so nothing is added. A tag of 80% purity and 85% germination gives 68% PLS, and 76 ÷ 68 = 1.12 pounds of seed per pound the rate calls for. Type both numbers from the seed tag and the calculator does it for you.