20x20 Patio Calculator

20 × 20 = 400 square feet (about 37.2 m²). Building a patio this size? Plan on roughly 4-5 tons flagstone and ~6.4 cubic yards (4" base, incl. compaction). The calculator below refines it for your stone.

A 20x20 patio provides 400 square feet - a substantial outdoor living space for serious entertainers.

Dimensions

20' x 20'

Area

400 sq ft

Size Category

Large

Materials Flagstone Cost Estimate

Calculate Materials for Your 20x20 Patio

Patio Area (square feet)

Pre-filled for 20x20 (20' x 20'). Adjust if needed.

Stone Type

Material Requirements

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Still shopping Compare local material or install options Carry your area and stone choice into the cost and local-match form. Stones are ready Plan it yourself — $29 Use one non-renewing Project Pass for this DIY job, or begin in the no-card planner. Want an expert plan Have James design it — $149 Have an experienced stonemason design the layout for your actual stones, or use the field guide with an installer you choose.

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About 20x20 Patio Patios

A 20x20 patio provides 400 square feet - a substantial outdoor living space for serious entertainers.

What a 20x20 Patio is Great For

Complete outdoor living space
Outdoor kitchen with dining and lounge
Fire pit area plus dining
Large pool deck

Design Tips for 20x20 Patios

Consider breaking the space into defined zones
A larger patio benefits from visual anchors like a fire pit or water feature
Plan pathways through the space for traffic flow

Quick Material Estimates

Stone (Flagstone)

4-5 tons flagstone

Base Gravel

~6.4 cubic yards (4" base, incl. compaction)

* Estimates vary by stone type. Use the calculator above for precise quantities.

Design First, Order Less

People typically over-order stones for a 20x20 patio. Design your layout digitally to know exactly what you need.

Upload photos of your actual stones
Arrange them to fit perfectly
Order only what you need

Plan My Delivered Stones

Other Patio Sizes

Small

Medium

Large

Extra Large

Material Tips

Base: Provides drainage and stability

Sand: Creates level surface for stones

Waste: 10% extra included for cuts and breakage

Related Resources

Your project, routed by what happens next

Where are you in the patio project?

Choose the closest stage. The article and calculators stay completely free and available.

01 I’m choosing a material

Compare cost, upkeep, climate fit, and appearance before you commit.

Compare flagstone, bluestone, and pavers Email me the free decision report

02 I need to know how much to order

Calculate stone, base gravel, and bedding sand without giving up your contact details.

Calculate my material order Check a stone waste allowance

03 My stones are delivered

Use one non-renewing Project Pass for this DIY job, or begin in the no-card planner.

Choose the DIY Project Pass Use the no-card planner instead

04 I want someone to plan or install it

Have an experienced stonemason design the layout for your actual stones, or use the field guide with an installer you choose.

See the Patio Design Service Use the DIY layout guide

20x20 Patio Patio FAQ

How many square feet is a 20x20?

A 20 by 20 foot area is 400 square feet (20 × 20 = 400), or about 37.2 square meters.

How much stone do I need for a 20x20 patio?

A 20x20 patio covers 400 square feet. For flagstone, you'll need approximately 4-5 tons flagstone. For standard pavers, calculate based on paver size. Always order 10-15% extra to account for cuts and breakage.

How much gravel do I need for a 20x20 patio base?

For a 20x20 patio (400 sq ft) with a standard 4-inch base, you'll need ~6.4 cubic yards (4" base, incl. compaction), already including the 30% compaction allowance. Use 6 inches of base for heavy-use areas or clay soil.

What furniture fits on a 20x20 patio?

A 20x20 patio (400 sq ft) is ideal for: Complete outdoor living space, Outdoor kitchen with dining and lounge, Fire pit area plus dining, Large pool deck. Consider your primary use when planning furniture placement.

Is a 20x20 patio big enough?

A 20x20 patio provides 400 square feet of outdoor living space. This is considered a large patio. A 20x20 patio provides 400 square feet - a substantial outdoor living space for serious entertainers. The right size depends on your intended use and available space.