Formula used
The calculator converts every measurement into square metres. It then applies the selected seeding rate. Adjustments account for quality, losses, soil, and slope conditions.
How to use the calculator
- Choose measured sections or enter a known area.
- Subtract patios, paths, beds, ponds, and buildings.
- Select the lawn purpose and suitable grass type.
- Confirm the seed label's recommended application rate.
- Enter germination, purity, losses, and site conditions.
- Add package size, pricing, taxes, and delivery costs.
- Calculate, review, copy, print, or export results.
Measure every lawn section using consistent dimension units. Keep exclusions in their selected area units. Verify final quantities against the seed manufacturer's current label.
New seeding versus overseeding
New lawns usually need more seed than established lawns. Overseeding fills thin areas without rebuilding the complete surface. Patch repairs often use concentrated rates for faster coverage.
Dormant seeding places seed before favourable spring conditions. Timing depends strongly on local soil and weather patterns. Regional guidance should determine the final spreading schedule safely.
Grass seed rate guide
| Grass type | New lawn | Overseeding | Patch repair | Dormant seeding |
|---|---|---|---|---|
| Kentucky bluegrass | 2.50 | 1.50 | 3.00 | 2.50 |
| Perennial ryegrass | 7.00 | 4.00 | 8.00 | 6.00 |
| Tall fescue | 8.00 | 5.00 | 10.00 | 8.00 |
| Fine fescue | 5.00 | 3.00 | 6.00 | 5.00 |
| Bermuda grass | 2.00 | 1.00 | 3.00 | 2.00 |
| Zoysia grass | 2.00 | 1.00 | 3.00 | 2.00 |
| Bahia grass | 10.00 | 5.00 | 12.00 | 9.00 |
| Centipede grass | 0.50 | 0.25 | 0.75 | 0.50 |
| Bentgrass | 1.50 | 1.00 | 2.00 | 1.50 |
| Buffalo grass | 3.00 | 2.00 | 4.00 | 3.00 |
Rates use pounds per 1,000 square feet. Confirm every rate using local guidance and the current product label.
Example seed estimates
| Lawn purpose | Area | Seed rate | Waste | Estimated seed |
|---|---|---|---|---|
| New lawn | 5,000 sq ft | 8 lb/1,000 sq ft | 10% | 44 lb |
| Overseeding | 5,000 sq ft | 4 lb/1,000 sq ft | 10% | 22 lb |
| Patch repair | 500 sq ft | 10 lb/1,000 sq ft | 15% | 5.75 lb |
These examples exclude germination, purity, establishment, soil, and slope adjustments.
Common mistakes
Do not measure the entire property as lawn area. Remove every permanent surface before calculating the seed requirement. Avoid combining dimension units inside one measured section.
Never assume one universal rate suits every cultivar. Read the bag label before accepting suggested default values. Recheck germination percentages when using older stored seed stock.
Frequently asked questions
How much grass seed do I need?
Multiply net lawn area by the recommended seed rate. Then adjust for quality, losses, waste, and site conditions. The calculator performs every conversion and package calculation automatically.
Should I use the new-lawn or overseeding rate?
Use new-lawn rates on bare prepared soil. Use overseeding rates where established grass already covers ground. Patch rates suit small, thin, or completely damaged areas.
Why does germination change the required quantity?
Not every seed produces a healthy established plant. Lower germination requires more applied seed for equal establishment. Use the tested percentage printed on the package label.
What does seed purity mean?
Purity measures the proportion containing the stated seed variety. Other material may include inert matter or different seeds. Lower purity increases the gross quantity needed for planting.
How much waste should I add?
Five to fifteen percent suits many routine projects. Complex shapes and steep slopes may justify additional seed. Avoid excessive allowances that create overly dense new growth.
Can I calculate several lawn sections?
Yes, add each section using its correct shape. The calculator combines areas before subtracting excluded surfaces. Mixed feet, yards, and metres are converted automatically.
How are circular lawn areas measured?
Enter the circle's radius rather than its diameter. Measure from the centre to the outside edge. The calculator applies pi times the radius squared.
Can I calculate a custom seed mixture?
Enable mixtures and add each variety's percentage share. Percentages must total exactly one hundred before calculation. Optional component prices create a blended purchase estimate.
Why is my bag count rounded upward?
Retail seed usually comes in complete sealed packages. Partial package purchases may not be available locally. Rounding upward prevents an avoidable shortage during spreading.
What does seed per application mean?
The final quantity divides across the selected spreading passes. Two perpendicular passes often improve distribution across irregular lawns. Each pass should spread only its assigned quantity.
Are the default rates guaranteed?
No, default rates provide general planning estimates only. Cultivars, climates, soils, and suppliers may recommend different rates. Always follow current regional advice and package instructions.
Planning disclaimer
This calculator provides estimates for lawn planning and purchasing. Actual results depend on seed, soil, weather, and technique. Follow local guidance and the product label before seeding.