20×20 Concrete Patio Cost: Quantities and Budget

A twenty-by-twenty-foot concrete patio has a four-hundred-square-foot footprint. Its cost depends on the specified slab assembly and the work required to make that footprint usable on the property. Calculate the actual quantities, then obtain current local proposals for preparation, concrete, placement, finishing, and related work.

Area is a starting input, not a complete price. A prepared open site and a replacement patio behind a restricted gate can require very different work. Use the same measured plan and construction assumptions when comparing quotations.

Confirm the footprint before calculating cost

Measure the intended outside dimensions and show the patio on a plan. A nominal twenty-by-twenty layout may change around the house, planting, or existing construction. Price the accepted footprint rather than a rounded description.

Check furniture and normal movement in that area. The four-hundred-square-foot patio design guide addresses usable arrangements. A cost calculation should follow a workable layout, not justify an area that fails to fit the intended activities.

Mark entrances, routes, edges, and any additional features. A roof support, step, raised element, or utility installation may need separate design and quantities beyond the basic slab.

Calculate concrete volume using design thickness

Multiply area in square feet by thickness in feet to obtain cubic feet. Divide cubic feet by twenty-seven to obtain cubic yards. Use the actual design thickness and include separately designed portions where relevant.

For an arithmetic comparison only, four hundred square feet at an assumed four-inch thickness equals about 133.33 cubic feet, or 4.94 cubic yards. At an assumed six inches, it equals two hundred cubic feet, or about 7.41 cubic yards.

Those thicknesses are calculation examples, not specifications for your patio. Loads, exposure, support, and project requirements determine the appropriate design. Have that decision resolved before ordering concrete or comparing supply allowances.

Keep measured quantities and ordering allowances separate

The eighty-foot perimeter applies only to an uninterrupted square. Connections, shaped edges, steps, and other details can change the forming scope.

Investigate excavation and support independently

The concrete volume is not the excavation quantity. Excavation depends on existing ground, finished levels, support layers, removal, and site conditions. The plan needs those dimensions separately.

For a quantity illustration, a four-hundred-square-foot footprint with a uniformly assumed eight-inch excavation would produce about 266.67 cubic feet before considering soil handling characteristics or other work. Eight inches is a fictional arithmetic input here, not a required excavation depth.

Ask the contractor how excavated material will be handled and measured. Disposal, unsuitable material, access, and restoration can affect the preparation price. Do not apply the concrete ordering quantity to an earthwork invoice.

Specify removal and disposal clearly

If an old patio occupies the area, identify its material, extent, and known construction. Determine what must be removed and which nearby features remain. Existing thickness or buried conditions may need investigation.

The patio replacement budget guide explains the broader removal relationship. A quotation for a new slab on prepared ground may omit demolition and disposal entirely.

Record who protects the house, routes, utilities, and retained planting during removal. Include restoration of affected access areas so the owner’s full project budget does not end at the new concrete edge.

Price the concrete specification and delivery

Provide the agreed concrete requirements to the supplier or contractor. Mixture and supply choices should follow the actual project and placement method. Do not select concrete solely by the lowest advertised price per yard.

Discuss delivery access, ordering allowance, and any equipment needed to convey material to the backyard. Supplier charges and delivery arrangements vary. Obtain the current terms rather than assuming every order includes the same services.

Keep the measured design volume identifiable beside the ordered quantity. That makes any allowance understandable and helps compare proposals without confusing material inside the slab with additional supply planning.

Include placement, finishing, joints, and care

The installation price should describe the crew and work that turn supplied concrete into a usable patio. Placement, finishing, joints, curing, protection, and cleanup should be allocated in the scope.

Choose the finish before requesting equivalent prices. Plain texture, exposed aggregate, color, or stamping can introduce different products and operations. A decorative allowance should not conceal missing underlying construction.

Confirm the actual protection and normal-use instructions at handover. Finishing the visible surface does not end the concrete process, and a generic waiting period may not suit the selected assembly or conditions.

Read a fictional budget for the full footprint

The following amounts are invented solely to demonstrate budget organization. They are not a current price range, contractor quotation, or U.S. average.

Dividing the illustrative $6,500 total by four hundred square feet gives $16.25 per square foot. That number describes this fictional scope only. Replace every line with actual local proposals and include any required work not represented here.

Identify items outside the basic example

Approvals, professional design, demolition, drainage changes, unsuitable ground, steps, walls, roof supports, electrical work, or other features may need additional scope. The fictional total does not establish that these items are unnecessary.

Separate owner purchases such as furniture from contractor construction. Confirm whether applicable taxes or fees are included. Avoid double-counting a charge already present in a quoted package.

Keep options separate from uncertainty. An optional decorative border is a choice, while a concealed site condition is an unresolved quantity or design question. They should not share an unexplained lump-sum line.

Compare complete prices on the same basis

Give bidders the same footprint, material requirements, finish, access information, and preparation assumptions. Ask them to identify differences instead of presenting a total without explanation.

The concrete patio quotation review guide helps check completeness. Compare included work and exclusions before calculating a unit price from each total.

If one proposal assumes prepared ground while another includes complete removal and restoration, reconcile those scopes first. A lower square-foot result may simply represent less work.

Use quantities to assess changes

An added section changes area and concrete volume, but it can also change perimeter, access, joints, and drainage. Ask for a revised plan and complete price effect rather than multiplying every change by the original rate.

As a simple area example, adding a four-by-twenty-foot strip adds eighty square feet. Whether that arrangement works depends on the connection and intended use. Resolve those details before treating the extra area as a purchase.

Keep authorized changes tied to measurable work and a stated reason. Updated quantities help explain the decision but do not replace the contractor’s revised scope.

Plan an allowance for genuine uncertainty

Reserve an appropriate owner allowance for unresolved work based on the investigation and proposals. Do not label a universal percentage as correct for every property. The amount should reflect the actual uncertainties.

Agree on how changed conditions are documented and approved. A contractor should explain additional work before the allowance is spent. Retain measurements and photographs where useful.

Once the design and site information improve, revise the preliminary budget. A measured plan with resolved preparation can reduce uncertainty, while a rounded area and generic national rate cannot.

Check sensitivity to a changed design input

Across four hundred square feet, one additional inch of uniform thickness represents about 33.33 cubic feet, or 1.23 cubic yards. That arithmetic shows why a quotation using an uncertain thickness can have a significant quantity difference. It does not authorize changing the design to achieve a cheaper order.

Likewise, shaped openings or excluded areas change the actual footprint. Mark them on the plan and use the accepted geometry. Review uncertain dimensions before fixing the concrete quantity, then ask the contractor to explain any corresponding change in preparation, joints, or labor. The material volume is one consequence of a design decision, while the complete project scope may change in several ways.

Retain the completed quantity and cost records

Keep the final drawing, specified assembly, measured quantities, ordered material information, authorized changes, invoices, and care instructions together. These records support later repair or extension planning.

The actual final cost is evidence for this project. It is not automatically the price of another four-hundred-square-foot patio with different access, conditions, or construction requirements.

How many square feet is a 20×20 patio?

It is four hundred square feet when the dimensions describe the complete rectangular footprint.

Is four inches the required thickness?

This guide uses it only as an arithmetic example. The appropriate thickness must follow the actual design and project conditions.

Can I budget using concrete volume alone?

No. Include preparation, delivery, placement, finish, joints, care, related work, and applicable exclusions to understand the total.