Grass Seed Calculator: How Much Seed Do I Need?
Find out how many pounds of grass seed you need from your lawn area and the seeding rate on the bag. New lawns seed heavier than overseeding — roughly double the rate.
Calculator
A 5,000 sq ft lawn at 4.0 lb per 1,000 sq ft needs about 20.0 lb of seed. New lawns seed heavier than overseeding (roughly half the rate) — the rate is a labeled typical, so use the number on your seed bag.
Formula
Grass seed is sold and applied by weight per unit area, so the math is a direct proportion:
seed (lb) = area (sq ft) × rate (lb per 1,000 sq ft) ÷ 1,000
The rate depends on the grass type and whether you are seeding bare ground or overseeding an existing lawn. New-lawn rates are roughly double overseeding rates. Both are labeled typicals — always use the number printed on your seed bag, which is calibrated to that specific blend.
Worked example
Say you are seeding a new 5,000 sq ft lawn with a tall-fescue blend at 4 lb per 1,000 sq ft:
- Multiply area by rate: 5,000 × 4 = 20,000.
- Divide by 1,000: 20,000 ÷ 1,000 = 20 lb of seed.
If you were overseeding that same lawn, you would use about half the rate (2 lb per 1,000 sq ft) and need only ~10 lb. Buy a little extra so you can go back over thin or bare patches.
How to get an accurate seed estimate
The single biggest source of error is the area, not the arithmetic. Measure the grass you actually want to seed — subtract the house footprint, driveway, beds and patio. If your yard is irregular, break it into rectangles, measure each, add them up, then feed the total into this tool. The lawn area calculator does exactly that.
New lawn vs. overseeding. Bare soil needs a full rate so seedlings knit into a dense turf; overseeding an existing lawn uses about half, because the established grass already fills most of the space. Dormant seeding and heavy-traffic repairs sit somewhere in between.
Grass type matters. Fine-seeded species like Kentucky bluegrass (~3 lb per 1,000 sq ft) go much further per pound than large-seeded tall fescue (~8 lb) or ryegrass (~7 lb); warm-season Bermuda is seeded very light (~1 lb). Match the rate to the blend and your region — cool-season in the north, warm-season in the south.
Timing and coverage. Early fall is the best window for cool-season seed; late spring for warm-season. Split the seed into two passes at right angles for even coverage, keep the top inch of soil consistently moist until germination, and remember these are planning typicals — the bag rate wins.
Reference table
Typical new-lawn seeding rates (labeled planning bands; overseeding uses about half). Confirm the rate on your bag.
| Grass type | New lawn (lb / 1,000 sq ft) | Overseed (~½) |
|---|---|---|
| Kentucky bluegrass | 3.0 | 1.5 |
| Tall fescue | 8.0 | 4.0 |
| Perennial ryegrass | 7.0 | 3.5 |
| Bermuda | 1.0 | 0.5 |