Artificial Grass & Base Build-Up Calculator

Artificial Grass Calculator

Calculate how much artificial grass you need for any lawn shape, plus weed membrane, MOT sub-base build-up and kiln-dried sand infill. Includes wastage allowance and 2026 UK pricing.

Last reviewed 29 July 2026
5 Lawn Shapes
Base Build-Up Included
Sand Infill Calculated
2026 UK Pricing
Rule of thumb: allow 5–15% wastage depending on lawn shape, a 50–100mm MOT Type 1 sub-base if laying on soil, and around 5 kg/m² of kiln-dried sand infill.
Lawn Details
Enter your lawn area and choose your grass grade

Mid-range: ~£14–£27/m². Good all-round density, suitable for family gardens and pets.

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5% is standard for rectangular lawns — auto-adjusts when you change shape.

Base Preparation

Installation Guide

How to Lay Artificial Grass

Artificial grass looks only as good as the base beneath it. Most failures — sinking, rippling, ponding water — trace back to skipped or rushed base preparation, not the grass itself.

Materials by Lawn Size (New Build-Up, 75mm Sub-Base)
Quick reference for common lawn sizes, mid-range grass grade
Lawn size Grass (10% waste) Sub-base (75mm) Sand infill
20 m² 22 m² ~2.7–3.0 t 100 kg
50 m² 55 m² ~6.8–7.5 t 250 kg
100 m² 110 m² ~13.5–15.0 t 500 kg
Sub-base weight assumes compacted MOT Type 1 at 1.8–2.0 t/m³. Infill at 5 kg/m² kiln-dried sand. For 50 m² and over, a loose tipper load is typically more cost-effective than bulk bags.

Base Preparation is Everything

Excavate to a depth of your chosen sub-base thickness plus a 20–25mm sharp sand blinding layer plus the grass and backing thickness (typically 20–35mm total). Lay MOT Type 1 in layers of no more than 50mm and compact each layer with a wacker plate — a single deep, loosely-compacted layer is the most common cause of a lawn that sinks or develops soft spots within its first year. Fall the base slightly away from the house (around 1:80) for drainage.

Weed Membrane and Edging

Lay a weed-suppressant membrane over the compacted, blinded base, overlapping joins by at least 150mm. Secure the perimeter with treated timber or metal edging before fitting the grass — this gives the U-pins something solid to fix into and creates a crisp, defined edge that won't fray or lift over time.

Laying, Jointing and Infill

Roll out the grass and allow it to relax for a few hours before trimming, so it lies flat. Always run the pile direction the same way across the whole lawn — mixing directions creates a visible colour/shade mismatch in different light. Butt roll edges together (never overlap) and bond joins underneath with seaming tape and polyurethane adhesive.

Fix the perimeter and joins with U-pins roughly every 150–200mm. Brush kiln-dried sand infill into the pile with a stiff broom or power brush in two or three light passes rather than one heavy one, working against the grain to help it settle to the base of the fibres.

Common Questions

Artificial Grass FAQs

Measure your lawn area in m² and add a wastage allowance — 5% for a simple rectangular lawn, 10% for curved or L-shaped areas, and 15% for complex shapes with multiple angles. Artificial grass is sold in fixed roll widths (commonly 2m or 4m), so actual order quantities often round up further depending on how the installer orientates the rolls to minimise seams.
Yes, unless you're laying directly onto an existing patio, decking or other hard, free-draining surface. On soil, a compacted MOT Type 1 sub-base (50–100mm depending on use) with a sharp sand blinding layer on top gives a stable, well-drained base that won't settle or pond water. Skipping this step is the most common cause of a lumpy, poorly-draining artificial lawn.
Yes. A weed-suppressant membrane laid over the compacted base (or directly over an existing hard surface) stops weeds growing up through the joints and keeps the sub-base from mixing with the soil beneath. It's a low-cost layer that prevents a significant long-term maintenance headache.
Most artificial grass products need kiln-dried sand infill brushed into the pile, typically at around 4–6 kg per m². Infill weighs the grass down, protects the backing from UV, helps blades stand upright, and improves drainage. Some premium non-infill products are designed without it — check your specific product's installation guide.
Yes, provided the surface is sound, free-draining and reasonably level. You can skip the MOT sub-base build-up entirely — just lay a shock pad or underlay (optional, for a softer feel) followed by the grass, fixed at the edges. Standing water or a badly cracked surface should be addressed first.
Good quality artificial grass typically lasts 15–20 years with normal domestic use, backed by manufacturer warranties of 5–10 years. Lifespan depends on UV exposure, footfall, and pile density — budget products with thinner, less dense pile wear and flatten faster than mid-range or premium products.
Butt the two edges together (never overlap them), and secure the join underneath with seaming tape and a polyurethane jointing adhesive, working the pile fibres across the join by hand once bonded so the seam isn't visible from above. Plan roll layout to run pile direction the same way across every join and to minimise the total number of seams.

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Grass Needed
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Sub-Base
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Infill
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