How much artificial grass do I need?

Measure your area (length x width) and add 10% for cutting waste and trimming. Artificial grass rolls are typically 2m or 4m wide, so plan your layout to minimise joins and waste. Always lay the grass in the same direction for a consistent look.

What sub-base do I need for artificial grass?

On soil, you need to remove the top 50-75mm and replace with compacted Type 1 aggregate (MOT). On concrete or paving, you can lay directly with a shock pad for comfort. The sub-base should be level and well-compacted with a slight drainage fall.

Do I need infill sand for artificial grass?

Kiln-dried sand infill (2-5kg per m²) helps weigh down the grass, keeps blades upright, and improves drainage. Not all grasses require it, but it generally improves performance and longevity. Brush it into the pile after laying.

How much does artificial grass cost per m²?

Budget grass costs £6-£10/m², mid-range £12-£20/m², and premium £22-£35/m². Installation typically adds £15-£30/m² including sub-base preparation. Higher quality grass looks more natural, feels softer, and lasts longer (15-20 years vs 8-10 for budget).

Do I need weed membrane under artificial grass?

Yes, always lay weed membrane on top of the sub-base before the grass. This prevents weeds growing through. Use a heavy-duty geotextile membrane, not basic landscape fabric. On concrete, membrane is not needed.

GardenCalcs

Artificial Grass Calculator — Materials & Cost Estimate

Calculate how much artificial grass, sub-base, weed membrane, and infill sand you need.

Area Length

Area length in m

Area Width

Area width in m

Grass QualityGrass quality

Existing SurfaceExisting surface

How We Calculate This

How The Calculations Work

Grass area: Length x Width + wastage allowance (default 10%)
Sub-base: Area x depth (mm) / 1000 x 1.7 (density factor for Type 1)
Weed membrane: Same area as grass (with wastage)
Joining tape: Length of joins needed (when width exceeds 4m roll width)
Infill sand: Area x kg per m² (typically 4 kg/m²)

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.