Use this lawn seed calculator to estimate how much grass seed to buy from your lawn area, grass type, project type, and a realistic 10% to 15% extra for overlap and touch-ups.
How to Use the Lawn Seed Calculator
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Enter your lawn area directly, or switch to length × width if that is easier for your yard.
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Choose the project type so the calculator can use a sensible default rate.
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Select the grass type, then edit the seed rate only if your bag label gives a different number.
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Add extra seed for overlap, patching, and normal spreading loss.
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Enter a bag size if you want a bag count, then round up.
Lawn Seed Formula
The core formula is simple:
Seed needed = Lawn area × Seed rate
Final seed amount = Seed needed × (1 + Overage percentage / 100)
Example: 120 m² × 35 g/m² = 4,200 g; then 4,200 g × 1.10 = 4,620 g (about 4.6 kg)
Why Grass Type Changes the Seed Rate
Different grasses use different seeding rates because seed size and growth habit are not the same. Kentucky bluegrass is usually seeded lighter, perennial ryegrass sits in the middle, and tall fescue is usually seeded heavier.
That is why a grass seed calculator needs more than square footage alone. The same 1,000 sq ft lawn can need very different amounts of seed depending on the species.
Rough Lawn Seeding Rate Chart
These are practical default rates for the calculator. Use the seed bag label or local extension advice if your product gives a more specific rate.
| Grass type | New lawn | Overseeding | Patch repair | Sports / high-traffic |
|---|---|---|---|---|
| Kentucky bluegrass | 12.2 g/m² (2.5 lb/1,000 sq ft) | 7.3 g/m² (1.5 lb/1,000 sq ft) | 9.8 g/m² | 14.6 g/m² (3.0 lb/1,000 sq ft) |
| Fine fescue | 22.0 g/m² (4.5 lb/1,000 sq ft) | 12.2 g/m² (2.5 lb/1,000 sq ft) | 17.1 g/m² | 24.4 g/m² (5.0 lb/1,000 sq ft) |
| Perennial ryegrass | 24.4 g/m² (5.0 lb/1,000 sq ft) | 14.6 g/m² (3.0 lb/1,000 sq ft) | 19.5 g/m² | 29.3 g/m² (6.0 lb/1,000 sq ft) |
| Tall fescue | 34.2 g/m² (7.0 lb/1,000 sq ft) | 19.5 g/m² (4.0 lb/1,000 sq ft) | 24.4 g/m² | 39.1 g/m² (8.0 lb/1,000 sq ft) |
| Bermuda grass | 3.7 g/m² (0.75 lb/1,000 sq ft) | 2.4 g/m² (0.5 lb/1,000 sq ft) | 3.0 g/m² | 9.8 g/m² (2.0 lb/1,000 sq ft) |
| Mixed lawn seed | 19.5 g/m² (4.0 lb/1,000 sq ft) | 9.8 g/m² (2.0 lb/1,000 sq ft) | 14.6 g/m² | 24.4 g/m² (5.0 lb/1,000 sq ft) |
New Lawn vs Overseeding
A new lawn needs more seed because you are covering bare soil. Overseeding uses less because existing turf already fills part of the area.
Patch repair usually falls between those two. Large bare spots act more like a new lawn than a light overseeding job.
Why Add 10% to 15% Extra Seed?
Extra seed covers overlap, edges, thin strips, and touch-ups after the first pass.
For a simple flat lawn, 10% extra is usually enough. For rough ground, slopes, patch repair, or lots of obstacles, 15% is safer.