Answer first
What this calculator tells you
Calculate the pounds and bags of grass seed needed for a lawn from its area and a seeding rate. Buy the right amount of seed for a new lawn or an overseeding job. Formula: Seed (lb) = area ÷ 1,000 × seeding rate (lb per 1,000 sq ft); bags = pounds ÷ bag size. At the worked-example inputs, the seed needed (lb) is 30. Holding every other input steady, moving lawn area (sq ft) from 4,000 to 6,000 moves the result from 24 to 36.
Transparent method
The formula
Buy the right amount of seed for a new lawn or an overseeding job.
Worked example
Example inputs
How to interpret the result
Seed is applied by weight over an area, at a rate printed on the bag. A 5,000 square foot lawn at 6 pounds per 1,000 square feet takes 30 pounds, which is six 5 pound bags. Overseeding a healthy lawn uses roughly half that rate.
At the worked-example inputs the seed needed (lb) is 30. It rises with lawn area (sq ft) and falls as seeding rate increases; bag size (lb) does not move it.
These are quantity estimates from the area and depth you enter. Real yards have slopes, curves and settling, and bulk materials vary in weight with moisture, so order a little extra and confirm coverage, bag sizes and rates with the product label or your supplier. Fertilizer and seed rates depend on your grass, soil and region, so follow the label and your local extension office.
Before you rely on it
What to check
Follow the bag for your variety. Tall fescue, bluegrass and ryegrass mixes have different rates, and more seed than the label calls for makes plants crowd and thin out.
The common error
Where people go wrong with grass seed calculator
Seeding at the wrong time. Cool-season grass does best in early fall, and a spring sowing meets summer heat before the roots are deep.
Sensitivity evidence
How lawn area (sq ft) changes the seed needed (lb)
Holding every other input at the worked-example value, moving lawn area (sq ft) from 4,000 to 6,000 moves the seed needed (lb) from 24 to 36: a spread of 12, or 40% of the worked-example result.
| Lawn area (sq ft) | Seed needed (lb) | Bags needed |
|---|---|---|
| 4,000 | 24 | 5 |
| 4,500 | 27 | 6 |
| 5,000worked example | 30 | 6 |
| 5,500 | 33 | 7 |
| 6,000 | 36 | 8 |
Every input, tested
Which input moves the seed needed (lb) most
Of the 3 inputs, seeding rate moves the seed needed (lb) most (5 across the range tested) and lawn area (sq ft) moves it least (6). Bag size (lb) does not change it at all.
| Input | Tested from | To | Seed needed (lb) at each end | Swing |
|---|---|---|---|---|
| Seeding rate | 3 lb: overseeding a lawn | 2 lb: light overseed of a healthy lawn | 15 to 10 | 5 (67%) |
| Lawn area (sq ft) | 4,500 | 5,500 | 27 to 33 | 6 (20%) |
| Bag size (lb) | 4 | 6 | 30 to 30 | none |
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Lawn area (sq ft) | 5,000 | Enter the lawn area (sq ft) used in this calculation. |
| Seeding rate | 6 lb: new tall fescue lawn | The pounds of seed per 1,000 square feet for the job. |
| Bag size (lb) | 5 | Enter the bag size (lb) used in this calculation. |
| Seed needed (lb) | 30 | |
| Bags needed | 6 | |
Inputs, definitions and assumptions
Lawn area (sq ft)
Enter the lawn area (sq ft) used in this calculation. The prefilled worked-example value is 5,000.
Seeding rate
The pounds of seed per 1,000 square feet for the job. The prefilled worked-example value is 6 lb: new tall fescue lawn.
Bag size (lb)
Enter the bag size (lb) used in this calculation. The prefilled worked-example value is 5.
How to use this calculator
- 1Verify the inputs. Gather lawn area (sq ft), seeding rate and bag size (lb) from your own documents; the prefilled values are examples.
- 2Save a baseline. The worked example puts the seed needed (lb) at 30. Store your own version of it as Scenario A.
- 3Test one change. Start with seeding rate, the input with the biggest effect here: switching seeding rate changes the seed needed (lb): 3 lb: overseeding a lawn gives 15; 6 lb: new tall fescue lawn gives 30; 4 lb: new kentucky bluegrass mix gives 20; 2 lb: light overseed of a healthy lawn gives 10.
- 4Check the boundary. Read the interpretation boundary above before acting on the result.
People also ask
Frequently asked questions
How do you calculate grass seed?
Seed (lb) = area ÷ 1,000 × seeding rate (lb per 1,000 sq ft); bags = pounds ÷ bag size. At the worked-example inputs the seed needed (lb) is 30.
What does the grass seed result mean?
Buy the right amount of seed for a new lawn or an overseeding job. At the worked-example inputs the seed needed (lb) is 30. It rises with lawn area (sq ft) and falls as seeding rate increases; bag size (lb) does not move it.
How much does lawn area (sq ft) change the seed needed (lb)?
Holding every other input at the worked-example value, moving lawn area (sq ft) from 4,000 to 6,000 moves the seed needed (lb) from 24 to 36, a spread of 12.
What are the limits of this grass seed calculator?
These are quantity estimates from the area and depth you enter. Real yards have slopes, curves and settling, and bulk materials vary in weight with moisture, so order a little extra and confirm coverage, bag sizes and rates with the product label or your supplier. Fertilizer and seed rates depend on your grass, soil and region, so follow the label and your local extension office. The tables on this page test lawn area (sq ft) only from 4,000 to 6,000; a value outside that range is not tabulated here.
Which input moves the seed needed (lb) most in the grass seed calculator?
Ranked by how far each moves the seed needed (lb) across the range tested: seeding rate (5, 67%) and lawn area (sq ft) (6, 20%). Bag size (lb) does not change it.
How much does seeding rate matter in the grass seed calculator?
The worked example uses 6 lb: new tall fescue lawn. With the other inputs left at the worked example, switching seeding rate changes the seed needed (lb): 3 lb: overseeding a lawn gives 15; 6 lb: new tall fescue lawn gives 30; 4 lb: new kentucky bluegrass mix gives 20; 2 lb: light overseed of a healthy lawn gives 10.
How much does bag size (lb) matter in the grass seed calculator?
The worked example uses 5. The seed needed (lb) does not depend on bag size (lb); it moves the bags needed from 8 to 5 instead when bag size (lb) goes from 4 to 6.
Which inputs change the bags needed in the grass seed calculator?
At the worked-example inputs it is 6. Lawn area (sq ft) takes it from 6 to 7, seeding rate takes it from 3 to 2 and bag size (lb) takes it from 8 to 5.
Do bulk materials settle after delivery?
Yes. Soil and mulch settle by 10 to 20 percent and stone compacts by about 10 to 15 percent, so round the order up rather than down.
Why is the tonnage different from what I expected?
Weight per cubic yard depends on the material and its moisture. Gravel is about 1.3 to 1.6 tons, sand about 1.3 to 1.4 and topsoil about 1.1, and rain adds to all of them.
How much water does a lawn need?
About 1 inch a week, counting rain, is a common target for cool-season grass. Water deeply two or three times a week rather than a little every day, so roots grow down.
Sources and evidence
Free Calculators Online is independent and is not affiliated with or endorsed by the source organizations. Educational estimates only.