Grass Seed Calculator
How much grass seed to buy for a new lawn or for overseeding, from the lawn’s area and the seeding rate printed on the bag, with the bags it takes.
Result
Enter new lawn rate on the label to see the result.
https://calcgallery.com/landscaping/grass-seed-calculator/
Results are estimates for planning only. Actual needs vary with site conditions, products and workmanship. Always confirm quantities with your supplier and follow local building codes and manufacturer instructions. Read the full disclaimer
How to use the Grass Seed Calculator
- Enter the lawn's area. Measure each rectangle of lawn and add them, leaving out beds, paths and the house.
- Choose new lawn or overseeding, and enter the matching rate from the seed bag in the unit the bag uses.
- Enter the bag weight to see how many bags to buy and how much will be left over.
The calculation
seed = lawn area × seeding ratebags = seed ÷ bag weight, rounded upA rate of 4 pounds per 1,000 square feet on a 5,000 square foot lawn is 5 × 4 = 20 pounds. The rate unit is the whole method: the page converts pounds per 1,000 square feet, pounds per acre and grams per square metre through their exact definitions and applies the number from the bag.
What the page leaves to the label
It stores no seeding rate for any grass. Rates depend on the species and the blend, on whether the product is coated, and on the purpose, and they are printed on every bag. Seeding outside the recommended season or on unprepared soil changes how much of the seed establishes, which no quantity can make up for.
With your numbers
- Seed = lawn area × seeding rate; bags = seed ÷ bag weight, rounded up
Quick reference
Bags round up; the seeding rate is the one on your bag.
| Job | Seed to spread |
|---|---|
| 5,000 sq ft at 4 lb, 7 lb bags | 20 lb |
| 5,000 sq ft overseeded at 2 lb | 10 lb |
| 1,000 sq ft at 6 lb | 6 lb |
| 10,000 sq ft at 3 lb, 20 lb bags | 30 lb |
| One acre at 200 lb per acre | 200 lb |
| 500 m² at 25 g/m², 5 kg bags | 12.5 kg |
| 200 m² overseeded at 15 g/m² | 3 kg |
Common questions about the Grass Seed Calculator
- How many bags of grass seed do I need?
- 3 bags of 7 pounds for a new lawn of 5,000 square feet at a label rate of 4 pounds per 1,000 square feet. That is 5,000 ÷ 1,000 × 4 = 20 pounds of seed, and 20 ÷ 7 = 2.9 bags, rounded up to 3 with 1 pound left over.
- How much grass seed do I need per 1,000 square feet?
- Whatever the bag says for that mix. Seeding rates differ several-fold between grasses, because seed size varies, so a pound of one grass holds many more seeds than a pound of another, and blends differ again. That is why this page asks for the rate instead of assuming one. Divide your area by 1,000 and multiply by the label rate: 5,000 square feet at 4 pounds per 1,000 is 20 pounds.
- Why is the overseeding rate lower than the new lawn rate?
- An existing lawn already has plants; the seed only has to fill thin spots between them. Most labels therefore give a second, lower rate for overseeding. Use the one printed for your situation, since the ratio between the two is not the same for every product.
- My bag gives the rate in pounds per acre. Does that change anything?
- Only the arithmetic. An acre is 43,560 square feet, so 200 pounds per acre is about 4.6 pounds per 1,000 square feet. Choose the unit your bag uses and the page converts it.
- Should I buy extra seed?
- The page rounds up to whole bags and shows what is left over. Some people keep the remainder to patch thin spots once the lawn comes up, which uses the same seed and matches the colour.