Grass seed calculator
Work out how much grass seed you need to sow or overseed a lawn, from its area and your chosen seeding rate.
Result
Grass seed required
How to use this tool
- Measure the length and width of the lawn area.
- Enter the rate stated on your seed packet or manufacturer's data. The presets are illustrative examples, not product instructions.
- Read the total seed weight required.
Assumptions
- Area multiplication is exact for the entered rectangular dimensions; seed quantity depends on the entered rate. The 35g/m² default and presets are illustrative only. Follow the selected seed mix's sowing rate and application instructions.
Technical details: what the fields mean
- Length
length - The longest side of the lawn area.
- Width
width - The other side of the lawn area.
- Seeding rate
seedingRate - Seed weight per square metre. This editable rate depends on the seed mix and whether you are sowing or overseeding; use the packet/manufacturer recommendation.
Methodology
Seed required = area × seeding rate. Rates vary by grass seed mix — check the specific product's recommended rate for the most accurate figure.
Worked example
10m × 6m lawn, example packet rate of 35g/m²
Inputs: Length: 10 m, Width: 6 m, Seeding rate: 35 g/m²
Result: 2.10 kg of seed. Use the rate for your seed mix and whether you are sowing a new lawn or overseeding.
Practical guidance
- Follow seed-packet or supplier guidance for timing and preparation; suitable conditions vary by seed mix, climate and local weather.
- Use the product's sowing instructions for preparation, application and watering.
Common mistakes
- Applying a new-lawn rate when overseeding, or the reverse; use the rate specified for the intended task.
- Treating seasonal timing suggestions as universal despite local weather and product instructions.
FAQs
How much grass seed do I need per square metre?
Use the packet or manufacturer's rate for your seed mix and task. For example, 60m² at an entered rate of 35g/m² takes 2.1kg; overseeding and establishing a new lawn may call for different rates.
How is grass seed for overseeding different from seed for a new lawn?
The required rate can differ. Enter the packet or manufacturer's rate for overseeding or new establishment as appropriate; this calculator does not prescribe one.
Last reviewed: 2026-10-11
A simple area × rate estimate — always follow the specific seed product's recommended rate where it differs from the default used here.
This tool provides an indicative estimate, based on the assumptions stated above.
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