How much artificial grass do I need?

Measure your area in metres (length x width), then add 10% for wastage and trimming. Artificial grass comes in 2m or 4m wide rolls, so you may need multiple strips joined together. Always lay rolls in the same direction so the pile faces the same way.

What sub-base do I need for artificial grass?

You need a 50mm layer of Type 1 MOT sub-base (crushed limestone/granite), compacted down, followed by a 10-15mm layer of sharp sand or granite dust as a levelling layer. This ensures proper drainage and a flat surface. For every 10 m² at 50mm depth, you need approximately 900kg (0.9 tonnes) of Type 1.

Do I need weed membrane under artificial grass?

Yes, always install a heavy-duty weed membrane between the sub-base and the grass. Standard landscaping fabric (100g/m² minimum) prevents weed growth through the drainage holes. Overlap joins by at least 150mm.

How long does artificial grass last?

Quality artificial grass typically lasts 15-20 years with proper installation and minimal maintenance. Premium products with UV stabilisation will retain colour better. Budget options may fade or flatten after 8-10 years. Brushing the pile occasionally helps maintain appearance.

How do I join artificial grass strips?

Use specialist artificial grass joining tape and adhesive. Lay the tape adhesive-side up along the join line, fold back both edges of grass, apply adhesive to the tape, then press both edges down onto the tape. Ensure the pile direction matches on both strips. Allow 24 hours for adhesive to cure.

Artificial Grass Calculator — How Much Fake Grass Do I Need?

Calculate artificial grass, sub-base, sand, membrane and fixings for your garden. UK roll sizes and materials.

Area Length

Longest dimension of your area

Area Width

Shortest dimension

Grass Quality

Select the grass quality for your calculation

Roll Width

4m rolls have fewer joins

Include wastage allowance

Adds 10% for trimming and fitting

Wastage Percentage

10% is standard for rectangular areas

Include weed membrane

Heavy-duty landscape membrane

Include Type 1 sub-base

50mm compacted MOT sub-base

Include sharp sand

15mm levelling layer

Grass Price per m² (optional)

Price of artificial grass per m²

How We Calculate This

Our artificial grass calculator works out all the materials you need for a complete installation, including the grass itself, sub-base preparation, weed membrane, and fixings.

The formula

Grass area = Length × Width × Wastage factor
Sub-base (kg) = Area × 0.05m depth × 1,800 kg/m³
Sharp sand (kg) = Area × 0.015m depth × 1,600 kg/m³
Edging pins = Perimeter ÷ 0.2m spacing

Installation layers

Sub-base: 50mm compacted Type 1 MOT (1.8 tonnes per m³)
Levelling layer: 15mm sharp sand or granite dust (1.6 tonnes per m³)
Weed membrane: 100g/m² minimum, 150mm overlaps
Artificial grass: Available in 2m and 4m wide rolls
Edging pins: Galvanised U-pins every 200mm around perimeter

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Verify with your supplier.