Landscaping
Grass Seed Calculator
Work out seed for overseeding or renovating an existing lawn.
Result
Overseeding only works where the seed reaches soil. Sown onto thatch or unprepared turf most of it never germinates, which is why aeration or scarifying beforehand matters more than the quantity.
Get a Free Business AuditWhat moves the number
- Overseeding rate, which is lower than for a new lawn.
- Whether the lawn is scarified or aerated first, which decides seed-to-soil contact.
- Existing sward density, since a thin lawn takes more seed than a patchy one.
Where this one goes wrong
Overseeding without creating soil contact. Seed scattered onto an existing sward sits in the thatch and does not germinate, so the scarification or aeration is the job rather than an optional extra.
Questions
About this calculator
Why does overseeding often fail?
Because the seed never reaches soil. Existing thatch and dense grass hold seed above the surface where it cannot germinate, which is why the preparation matters more than the seed rate.
Should the lawn be scarified first?
For most overseeding, yes. Removing thatch and opening the surface is what gives seed somewhere to establish.
How does overseeding rate compare to new sowing?
Lower, because the existing grass is already covering ground. Using a full establishment rate on an existing lawn is expensive and unnecessary.
The formula
pounds = area / coverage per pound
Put this calculator on your site
Free to embed. Paste this where you want it to appear. It stays up to date automatically because it loads from BDEVY.
Please keep the attribution line. It is the only thing we ask in return.
How to use this calculator
- Length (ft) (ft). Enter your own figure; the page starts at 60 ft.
- Width (ft) (ft). Enter your own figure; the page starts at 40 ft.
- Coverage per pound (sq ft) (sq ft). Enter your own figure; the page starts at 350 sq ft.
- Waste allowance (%). Extra for cuts, breakage and offcuts.
- Cost per pound ($). Enter your own figure; the page starts at $6.5.
The result updates as you type, so you can try a figure, see what it does to pounds of seed, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Length (ft) | 60 ft |
| Width (ft) | 40 ft |
| Coverage per pound (sq ft) | 350 sq ft |
| Waste allowance | 5% |
| Cost per pound | $6.5 |
What comes out
| Result | Value |
|---|---|
| Pounds of seed main result | 8 |
| Area | 2,400.0 |
| Area including waste | 2,520.0 |
| Estimated material cost | $52 |
For 2,400.0 sq ft plus 5% waste you need 8 pounds, costing about $52.
How sensitive the answer is
Holding everything else steady and changing only cost per pound, this is what happens to pounds of seed. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Cost per pound ($) | Pounds of seed |
|---|---|
| $3.25 | 8 |
| $4.88 | 8 |
| $6.5 example above | 8 |
| $9.75 | 8 |
| $13 | 8 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Length (ft) (ft)
- Measured in ft, starting at 60 ft.
- Width (ft) (ft)
- Measured in ft, starting at 40 ft.
- Coverage per pound (sq ft) (sq ft)
- Measured in sq ft, starting at 350 sq ft.
- Waste allowance (%)
- Extra for cuts, breakage and offcuts.
- Cost per pound ($)
- A money amount, starting at $6.5.
What the results tell you
| Result | What it is |
|---|---|
| Pounds of seed | The headline result. A number. |
| Area | A decimal figure. |
| Area including waste | A decimal figure. |
| Estimated material cost | A money figure. |
Seasonality is not in this
Coverage and material figures assume the area you enter. Slope, access for machinery, existing growth and the time of year all affect both quantity and labour, and none of them appear in a calculation like this.
Estimating is the easy part
The jobs you never hear about cost more than the ones you mis-measure. BDEVY builds the marketing, systems and automation that bring them in.