Grass seed calculator
Enter the lawn area and the seeding rate printed on the pack to see how much to buy.
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How to use it
- Enter length, width, seeding rate and bag weight.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Seed (kg) = length × width × seeding rate (g/m²) ÷ 1000. Bags = seed ÷ bag weight, rounded up.
Example
Inputs: Length = 20 m, Width = 10 m, Seeding rate = 35 g/m², Bag weight = 5 kg. Result: Seed needed: 7 kg; Bags: 2; Area: 200 m².
Limits and caveats
- Seeding rates vary widely by grass type, so use the rate your supplier recommends.
- Some warm-season grasses are planted from sprigs or turf rather than seed.
Questions about this tool
What seeding rate is typical?
Many cool-season mixes suggest about 25 to 40 g/m² for a new lawn and roughly half that for overseeding.
Should I add extra seed?
Too much seed causes crowding and weak growth; stick to the pack rate and keep a little back for patching.
When should I sow in a hot climate?
Usually in the cooler months, from autumn to early spring, with light regular watering until it germinates.