Concrete Patio Calculator: 12x12 = 1.96 yd3, 88 Bags

A 12 ft by 12 ft concrete patio at 4 inches thick needs about 1.96 yd3 with 10% waste, or about 88 80-lb bags. A 20 ft by 20 ft patio at the same thickness needs about 5.43 yd3 with 10% waste, or about 245 80-lb bags, so the 20x20 job should be quoted as ready-mix, buggy, pump, or contractor placement before anyone buys bags.

Estimate your dimensions with the Concrete Patio Calculator, then use the tables below to check quantities and compare the scope of a supplier or contractor quote.

This concrete patio calculator guide estimates cubic yards, 40/60/80 lb bag counts, ready-mix material cost, and installed quote checks for common 12x12, 16x20, and 20x20 patio sizes. Measure length and width, choose a planning thickness, add waste, then compare bags, ready-mix, backyard access, finish scope, and contractor pricing without confusing material-only cost with installed patio cost.

Sources and checks

Manufacturer yields, supplier delivery conditions, and installed-cost benchmarks answer different questions. Use the product label and local written quote for the material you are actually buying.

If the yield printed on your bag is different from the common 0.30, 0.45, or 0.60 ft3 assumptions, use the printed yield and rerun the calculator before buying.

If you already know the cubic yards and only need pricing, use the Concrete Cost Calculator. If you are deciding between bags and delivery, use the Ready-Mix vs Bags Calculator. If a contractor bid is already in hand, run the numbers through the Concrete Quote Reviewer so delivery, pump, buggy, base prep, finish, disposal, and wait-time gaps do not hide inside one lump sum. If a contractor quote is written by square foot, use the Concrete Patio Cost per Square Foot Guide to separate ready-mix material from installed patio scope. For a calculator-first price worksheet, use the Concrete Patio Cost Calculator Guide. If the patio needs a compacted stone layer before the pour, estimate the base material with the Concrete Gravel Base Calculator. For worked base examples, see the Gravel Base Calculator for Concrete guide. If the patio area must be excavated, graded, or hauled off before the base is placed, use the Concrete Excavation Cost Calculator Guide. If water collects near the patio, doors, foundation, or low yard edge, separate the slab estimate from the drainage scope with the Concrete Patio Drainage Cost Guide. For fall-per-foot checks before forms are set, use the Concrete Patio Slope Calculator Guide. For patio delivery access, check whether the ready-mix chute can reach with the Concrete Truck Chute Reach Guide. If the truck must use or avoid a residential driveway, review the Concrete Truck Driveway Access Guide before scheduling delivery. If you plan to move concrete from the driveway by hand, estimate trips and unload time with the Concrete Wheelbarrow Distance Calculator Guide. If the ready-mix truck cannot reach the patio forms, compare buggy access in the Concrete Buggy Rental Cost Guide.

If you are estimating a long narrow walkway instead, see the Concrete Sidewalk Calculator Guide. If you are comparing a patio slab with patio pavers, use the Concrete Paver Calculator Guide to estimate paver count, base, sand, waste, and paver-specific quote lines. For the full pavers vs concrete patio cost decision, use the Pavers vs Concrete Patio Cost Guide. For poolside flatwork, use the Concrete Pool Deck Cost Calculator Guide so the deck area, drains, coping transitions, and backyard access stay separate from a simple patio rectangle.

This guide connects two decisions: how much concrete the patio needs, and how to read a patio quote. The yardage calculation checks the material quantity; the square-foot and finish sections help you understand why installed patio quotes can vary so much.

Patio quantities at a glance

For a rectangular patio, multiply length by width by thickness, divide by 12 and 27, then add waste. A 12 ft by 10 ft patio at 4 in thick needs about 1.48 yd3 before waste, or 1.63 yd3 with a 10% waste factor.

For a more common square patio example, a 12 ft by 12 ft patio at 4 in thick needs about 1.78 yd3 before waste, 1.96 yd3 with 10% waste, or about 88 common 80 lb bags. A 20 ft by 20 ft patio at 4 in thick needs about 5.43 yd3 with 10% waste, which is about 245 common 80 lb bags and is usually a ready-mix project.

The quantity tables use 4 inches of thickness, 10% waste, and common yields of 0.30, 0.45, and 0.60 ft3 for 40, 60, and 80 lb bags. Bag counts use unrounded volume and round up only at the end. For the illustrative ready-mix prices, multiply the displayed two-decimal yardage by $165/yd3 and add a $125 delivery fee. Those prices deliberately use rounded yardage; a supplier may round order quantities differently. These are example prices, not local quotes.

The calculator result is a material planning number. A real patio quote can also include excavation, grading, gravel base, forms, reinforcement, control joints, finishing, curing, sealer, old patio removal, access, and labor. Finish choice matters too: a plain broom-finished slab is a different project from a stamped, stained, or bordered patio.

Common patio size answers

Compare eight rectangular patio sizes using the same assumptions above.

If the answer is under about 50 bags, bagged concrete may still be worth pricing. Once the answer is dozens or hundreds of bags, compare ready-mix, buggy, pump, and contractor placement before choosing the cheapest material line.

For bag coverage by thickness, see the 40, 60, and 80 lb concrete bag coverage chart. For installed cost scope, compare this material table with the Pavers vs Concrete Patio Cost Guide and any contractor quote.

Concrete patio formula

For a rectangular patio:

cubic yards = length ft x width ft x thickness in / 12 / 27

Then add waste:

order quantity = cubic yards x (1 + waste percent / 100)

For 10% waste, enter 10 in the formula, giving a multiplier of 1.10. Keep the full volume until the final display or whole-bag count; 12x12 at 4 inches is 52.8 ft3 after waste, and 52.8 / 0.60 = 88 bags.

For irregular patios, split the layout into rectangles, calculate each section, then add the totals before applying waste. If the patio has a step pad, grill pad, fire pit extension, or separate walkway connection, estimate those sections separately so the quote is easier to check.

For other slab shapes and uses, use the Concrete Slab Calculator. For the broader yardage calculation, see How Many Yards of Concrete Do I Need?.

Best calculator inputs for patio planning

Use inputs that match the actual patio scope, not only the simple rectangle in your first sketch. A patio often grows once you include landings, grill pads, steps, drains, borders, or a widened seating area.

Run one estimate for the plain slab, then run a second version with every extra pad or widened area included. That shows whether the budget changed because of concrete quantity or because of finish, access, demolition, or site-prep scope.

Common patio project scenarios

The same slab formula works for most patios, but the surrounding scope changes the installed quote. Split the concrete quantity from the project decisions before comparing bids.

A plain slab and a decorative outdoor-living patio can use the same volume but require different preparation, finish work, and access arrangements.

2026 patio cost sanity check

Patio cost pages often quote installed cost by square foot. That is useful for checking a bid, but it is not a substitute for the cubic-yard calculation. Square-foot pricing usually includes labor and scope items that are not inside a concrete material estimate.

For external benchmarks, the Homewyse concrete patio cost calculator states a May 2026 national starting estimate of $10.30 to $12.64 per square foot. Its basic labor description excludes excavation, gravel base, compaction, and hardscape demolition. Location, area, and selected options change its customized estimate; the national range is not a quote for your project. For a separate quantity check, Concrete Network's concrete calculator estimates yards and bag counts from slab dimensions. Neither quantity output nor a national cost benchmark replaces a local written scope and price.

Use both checks:

installed quote per sq ft = contractor quote / patio square feet
ready-mix material = cubic yards after waste x price per yard + delivery fees

The installed number can change quickly based on:

If a contractor quote looks high compared with the material estimate, check finish type, base prep, access, demolition, drainage, and warranty before assuming the concrete price is the reason. If the quote is competing against patio pavers, compare the same finished area with the Pavers vs Concrete Patio Cost Guide before choosing by square-foot price alone. For a focused old-slab demolition and haul-off workflow, use the Concrete Slab Removal Cost Guide, then separate disposal with the Concrete Disposal Fee Guide. For backyard patios where the truck cannot reach the forms, use the Concrete Pump Cost Calculator Guide to compare pump, buggy, wheelbarrow, and wait-time costs.

Example: 12 ft by 10 ft patio

Assume:

• Length: 12 ft
• Width: 10 ft
• Thickness: 4 in
• Waste: 10%

Base volume:

12 x 10 x 4 / 12 / 27 = 1.481481... yd3

With waste:

(12 x 10 x 4 / 12 / 27) x 1.10 = 1.629629... yd3

Planning estimate: about 1.63 cubic yards after waste.

At $165 per yd3 and a $125 delivery or short-load fee:

1.63 x $165 = $268.95
$268.95 + $125 = $393.95

This is still a material-only estimate. It does not include base preparation, forms, reinforcement, finishing, control joints, cleanup, taxes, or contractor labor.

If a 120 sq ft patio quote is $1,800:

$1,800 / 120 sq ft = $15.00 per sq ft

That installed cost includes a broader scope than the $393.95 ready-mix example. Ask what is included before comparing it with other bids.

Example: 20 ft by 20 ft patio

A larger 20 ft by 20 ft patio at 4 in thick is:

20 x 20 x 4 / 12 / 27 = 4.938271... yd3
(20 x 20 x 4 / 12 / 27) x 1.10 = 5.432098... yd3

At $165 per yd3 and a $125 delivery fee:

5.43 x $165 = $895.95
$895.95 + $125 = $1,020.95

For a patio this size, ready-mix should usually be part of the quote. Hundreds of bags can create handling, timing, and cold-joint problems.

Bag count for a patio

If you use 80 lb bags with a common 0.60 ft3 yield:

(12 x 10 x 4 / 12) x 1.10 = 44 ft3
44 / 0.60 = 73.333333... bags
round up to 74 bags

That is a lot of mixing for one continuous patio slab. If the estimate is dozens of bags, compare delivery before buying bags.

For bag yield and coverage details, see How Much Is a Bag of Concrete? and Concrete Bags per Yard. For a side-by-side buying comparison, see Ready-Mix vs Bags Cost.

Bag count pressure table

Bagged concrete can work for a small pad or repair, but patio-sized pours can cross into ready-mix territory quickly.

If the result is high, the decision is no longer only material price. You also need a plan for placement speed, finish timing, joints, cleanup, and weather.

DIY, supplier, or patio contractor?

Use the calculator result to choose the next conversation, not just the shopping list.

For a tiny pad, bags may be the practical path. For a patio-sized continuous slab, the more valuable question is who can place, finish, joint, and cure the concrete before timing becomes the problem.

Material cost vs project cost

For ready-mix:

ready-mix total = cubic yards after waste x price per yard + delivery fees

Use this broader planning formula for a patio project:

project total =
  concrete material
  + delivery or short-load fees
  + excavation, grading, base, and forms
  + reinforcement, joints, finishing, curing, and sealer
  + demolition, cleanup, permits, and labor

Patio cost guides often discuss installed pricing by square foot, but a material calculator should stay separate from installed project cost. A stamped or stained patio, an old slab removal, poor access, a hot tub pad, a covered patio, or a drainage correction can change the quote quickly.

For a broader material-only pricing workflow, see Concrete Cost per Yard.

Demolition, access, and drainage scope

Patio quotes can move sharply even when the cubic-yard number is the same. Before accepting a bid, ask whether these items are included:

• Removal and haul-off of old concrete, pavers, deck footings, or soil.
• Regrading and compacted base correction after demolition.
• Truck access, chute reach, pump, buggy, wheelbarrow route, and lawn repair.
• Drainage slope away from the house, doors, window wells, and low spots.
• Isolation joints where the patio meets the house, steps, posts, or an existing slab.
• Sealer timing and whether decorative finishes require maintenance.

Keep demolition and access as separate quote lines. They may not change the new patio volume, but they can change the project price and schedule.

Finish and add-on quote checks

Patios often vary more by finish and site conditions than by concrete volume. Before you compare bids, normalize the finish:

This helps avoid comparing a plain slab bid with a decorative patio bid.

Ready-mix quote checklist

If you order concrete directly, ask the supplier for:

• Cubic yards after waste and how they round the order.
• Price per yd3, delivery, short-load fee, fuel surcharge, tax, and waiting time.
• Mix strength, air entrainment if needed, fiber, additives, and slump target.
• Truck access, chute reach, pump, buggy, or wheelbarrow distance.
• Minimum order, cancellation window, and weather policy.
• Whether the supplier only delivers concrete or provides any placement help.

Then compare that supplier quote with the material line in the patio contractor bid.

Patio thickness planning

Many patio estimates use 4 in as a planning thickness, but the right design depends on load, base preparation, drainage, soil, reinforcement, local code, and whether the patio will carry heavy outdoor kitchens, hot tubs, masonry features, or vehicles.

Use a calculator for material planning only. Do not treat it as structural, drainage, or permit approval. For more thickness context, see the Concrete Slab Thickness Guide.

Slope, joints, and house transitions

Concrete patios near a home need water and movement details, not just volume. Review these items before ordering:

• Slope should move water away from the house and away from door thresholds.
• The slab should not trap water against siding, posts, steps, or window wells.
• Control joints do not usually change concrete quantity, but they should be planned before the pour.
• Isolation joints may be needed where the patio touches the house foundation, stairs, garage slab, posts, or an existing walkway.
• Decorative finishes still need joint planning; pattern work does not remove shrinkage or movement concerns.

If the bid does not describe slope, transitions, or joints, ask for those items in writing before comparing the installed price.

Patio estimating checklist

• Measure the actual formed dimensions before ordering.
• Confirm thickness, base depth, compaction, and drainage slope.
• Add a waste factor, often 5% to 10% for simple flatwork planning.
• Decide whether bags are practical for the bag count.
• Ask ready-mix suppliers about short-load fees, minimum loads, delivery access, waiting time, and tax.
• Confirm finish type, control joints, curing, sealer, and weather timing.
• Include old patio removal, permits, cleanup, and access equipment when relevant.
• Do not use a material calculator as structural approval.

Quote checklist for contractors

Before accepting a patio bid, ask what is included in writing:

• Exact dimensions, total square footage, and thickness.
• Base material, base depth, compaction, and grading.
• Reinforcement type, if any.
• Control joint spacing and whether joints are tooled or saw cut.
• Finish type, color, stamping, borders, or sealer.
• Drainage slope away from the house and transitions to doors or steps.
• Removal and haul-off of old concrete, pavers, or soil.
• Truck access, chute reach, pump, buggy, or wheelbarrow placement.
• Weather delay policy, cleanup, warranty, and payment schedule.

That checklist helps turn a patio calculator result into a cleaner quote conversation.

Bid comparison table

Use a table like this when two patio quotes are hard to compare:

The best quote is the one that is specific enough to compare, not simply the lowest number.

Patio bid red flags

These red flags do not automatically disqualify a bid, but they are reasons to ask for the missing detail before comparing prices.

A strong patio estimate should separate material quantity, site prep, finish, access, and warranty. If those pieces are blurred together, use the calculator result to ask better follow-up questions before choosing the bid.

Patio quote triage by problem

Use the calculator result as the quantity baseline, then route the quote to the problem that will actually change the price.

Check access, drainage, finish, and exclusions alongside the yardage before comparing the final price.

Common estimating mistakes

• Pricing by square feet without checking thickness.
• Forgetting a step pad, grill pad, fire pit area, or walkway connection.
• Treating material-only cost as the installed patio cost.
• Ignoring short-load fees for small ready-mix orders.
• Planning a bagged pour that is too large to place consistently.
• Comparing quotes without matching finish, base prep, removal, and sealer.
• Ignoring slope and drainage near the house.

FAQ

What calculator should I use for a concrete patio?

Use the Concrete Patio Calculator for patio quantities and patio-specific access, slope, and quote checks. The material calculation uses length, width, thickness, and waste factor.

How thick should a concrete patio be?

Four inches is a common planning thickness for many patios, but site conditions, loads, base preparation, reinforcement, drainage, and local requirements can change the correct thickness.

Can I pour a patio with bags?

Small patio sections may be possible with bags. A full patio can require dozens or hundreds of bags, so compare ready-mix delivery and placement logistics before buying.

Does the estimate include labor?

No. These calculations are material-only estimates. Labor, base preparation, forms, reinforcement, finishing, cleanup, and permits are separate.

How many yards for a 12x12 patio?

A 12 ft by 12 ft patio at 4 in thick is about 1.78 yd3 before waste. With 10% waste, plan around 1.96 yd3 before ordering or pricing.

How many bags for a 12x12 concrete patio?

At 4 in thick with 10% waste, a 12 ft by 12 ft patio is about 1.96 yd3. With common yields, that is about 88 80 lb bags, 118 60 lb bags, or 176 40 lb bags.

How many yards for a 16x20 patio?

A 16 ft by 20 ft patio at 4 in thick is about 3.95 yd3 before waste. With 10% waste, plan around 4.35 yd3 before pricing ready-mix or comparing quotes.

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

A 20 ft by 20 ft patio at 4 in thick is about 4.94 yd3 before waste and about 5.43 yd3 with 10% waste. That is about 245 80 lb bags, so most 20x20 patios should be priced as ready-mix or contractor projects before buying bags.

What costs are missing from a material-only patio estimate?

Common missing costs include excavation, grading, gravel base, compaction, forms, reinforcement, control joints, finish upgrades, sealer, old slab removal, cleanup, permits, taxes, and contractor labor.

Does stamped concrete change the estimate?

The concrete volume may be similar, but stamped or stained concrete can change labor, color, release agent, sealer, pattern work, and repair complexity. Keep material volume separate from finish pricing.

Why is a patio contractor quote higher than the concrete material estimate?

The material estimate only covers concrete quantity and sometimes delivery. The installed quote may include excavation, gravel base, compaction, forms, reinforcement, control joints, finishing, sealer, demolition, cleanup, overhead, warranty risk, and local labor.

What should I check before accepting a low patio bid?

Confirm dimensions, thickness, base prep, drainage slope, finish, control joints, old slab removal, sealer, cleanup, warranty, and whether permits or inspection requirements are included.

Should a concrete patio slope away from the house?

Yes, patio drainage should be planned so water does not collect against the house, doors, posts, or low spots. The exact slope and transition details depend on the site and local requirements.

Do control joints change patio yardage?

Usually no. Control joints are part of the cracking and finishing plan, not a major volume change. They still matter because joint layout and timing affect how the finished patio performs.

Should I calculate a grill pad or step pad separately?

Yes. Estimate extra pads, widened corners, step landings, and walkway connections as separate slab sections. This makes the yardage easier to verify and the contractor quote easier to compare.

Does old patio removal affect the concrete estimate?

Old patio removal may not change the new concrete volume, but it can change the project price. Demolition, haul-off, disposal, base repair, and cleanup should be listed separately in the quote.

Next step

Estimate your patio in the Concrete Patio Calculator, then compare material pricing in the Concrete Cost Calculator or Ready-Mix vs Bags Calculator. For written pricing context, read Concrete Cost per Yard and Ready-Mix vs Bags Cost.