How to calculate how much grass seed you need
Grass seed is applied at a set weight per 1,000 square feet, and the rate depends on the type of grass and whether you are starting from bare soil or thickening an existing lawn. Measure your lawn area, divide by 1,000 and multiply by the seeding rate.
Pounds of seed = lawn area (sq ft) ÷ 1,000 × seeding rate (lb per 1,000 sq ft)
For a rectangle multiply length by width; for a circle use π × radius²; for a triangle use base × height ÷ 2. Subtract anything that will not be seeded, such as paths and beds. Choose a seed type and the calculator fills in a typical rate, which you can edit to match your seed bag.
Example: a 100 ft × 50 ft lawn
- Area: 100 × 50 = 5,000 sq ft, which is 5 units of 1,000 sq ft
- New tall fescue lawn at 8 lb per 1,000 sq ft: 5 × 8 = 40 lb, or four 10 lb bags
- Overseeding the same lawn at 4 lb per 1,000 sq ft: 5 × 4 = 20 lb
- New Kentucky bluegrass at 2 lb per 1,000 sq ft: 5 × 2 = 10 lb
Seeding rates by grass type
The table lists the working rates used by the calculator, with the commonly quoted range in brackets. Rates differ between sources, varieties and blends, and coated seed weighs more per seed, so these are planning figures rather than rules. Always follow the rate printed on your seed bag if it differs. The germination times are approximate and depend on soil temperature and moisture.
| Grass type | New lawn | Overseeding | Typical germination |
|---|---|---|---|
| Kentucky bluegrass | 2 (1.5–3) | 1 (0.5–1.5) | 14–30 days |
| Perennial ryegrass | 7 (5–10) | 4 (3–6) | 5–10 days |
| Tall fescue | 8 (6–10) | 4 (3–6) | 7–14 days |
| Fine fescue | 4 (3–5) | 2 (1.5–3) | 7–14 days |
| Bermudagrass (hulled) | 1.5 (1–2) | 1 (0.5–1.5) | 7–21 days |
New lawn versus overseeding
A new lawn needs a high rate because you are relying on the seed to fill all of the bare soil. Overseeding adds seed to an existing lawn that has thinned out, so you need roughly half as much. For the best results, mow low, rake out dead material and loosen the surface first so the seed reaches the soil. Keep the top layer moist until the seedlings are established; watering lightly once or twice a day for the first few weeks is common advice.
If your soil is poor or uneven, a layer of quality soil first can help; work out the amount with the topsoil calculator. If you want an instant lawn instead, compare with the sod calculator. For any other volume, use the cubic yard calculator.
Frequently asked questions
How much grass seed do I need for 1,000 square feet?
It depends on the grass type: about 2 lb of Kentucky bluegrass, 4 lb of fine fescue, 7 lb of perennial ryegrass or 8 lb of tall fescue for a new lawn. Overseeding takes roughly half as much.
How much grass seed do I need for overseeding?
Use about half the new-lawn rate. For tall fescue that is around 4 lb per 1,000 sq ft, so a 5,000 sq ft lawn needs about 20 lb.
How many bags of grass seed do I need?
Divide the pounds of seed by the bag size and round up. For example, 40 lb of seed is four 10 lb bags, two 20 lb bags or one 50 lb bag. The calculator shows counts for several bag sizes.
Can I put down more seed than the recommended rate?
Using much more seed than the label recommends does not give a better lawn. Seedlings crowd one another, compete for water and become more prone to disease, so stay close to the recommended rate.
How long does grass seed take to germinate?
Perennial ryegrass can sprout in 5 to 10 days, tall and fine fescue in about 7 to 14 days, and Kentucky bluegrass can take 14 to 30 days. Warm soil and steady moisture speed things up.
More free calculators
These calculators give estimates for planning only. Densities, bag sizes and coverage vary by supplier, so confirm quantities before you order.