Calculate concrete needed for a patio slab. Enter length, width, thickness, and waste factor to get cubic yards and bags.
Building a concrete patio is one of the most popular backyard improvement projects. A well-constructed patio provides a level, durable surface for outdoor furniture, grilling, entertaining, and relaxation. The key to success is accurately estimating the concrete needed and planning for a proper pour.
This calculator helps you determine the volume of concrete required for your patio project. Enter the length, width, and thickness of the slab, and the calculator accounts for a waste factor to ensure you order enough material. Results are shown in cubic yards (for ready-mix ordering) and bag counts.
Most patios use 4-inch thick concrete, which provides adequate strength for foot traffic and patio furniture. If you plan to park heavy equipment or place a hot tub on the patio, consider increasing to 5 or 6 inches.
This data-driven approach helps contractors minimize rework, avoid delays caused by material shortages, and deliver projects on time and within the agreed budget.
Ordering the right amount of concrete for a patio prevents costly short-pours and wasted material. This calculator includes a waste factor for subgrade variations, edge overpours, and spillage so you order with confidence. It also helps compare the cost of bags vs. ready-mix delivery. Accurate figures enable contractors to prepare competitive bids with confidence, reducing the risk of underestimating costs or overcommitting on project timelines and deliverables.
Volume = Length (ft) × Width (ft) × Thickness (in) ÷ 12 With waste: Volume × (1 + waste %) Convert to yd³: ÷ 27
Result: 2.37 yd³
Patio: 16 ft × 12 ft × 4 in = 192 ft × 0.333 ft = 64 ft³ = 2.37 yd³ (with 5% waste: 2.49 yd³). At ~$160/yd for delivered concrete, that's approximately $398 for the material.
Minimum recommended size is 10×10 feet for a small seating area. 12×16 feet comfortably fits a table and four chairs. 16×20 feet accommodates a full outdoor dining set plus seating area. Consider shape: rectangles are easiest, but curved edges create visual interest.
Remove all topsoil and organic material down to undisturbed native soil. Add compacted gravel base (Class 5 or ¾" minus). Use a plate compactor for the gravel. The top of gravel should be uniform so concrete thickness is consistent.
Welded wire mesh (6×6 W1.4/W1.4) is standard for patios. Place on chairs at mid-depth of the slab. Fiber reinforcement (synthetic or steel fibers in the mix) is an alternative that eliminates the need to set mesh. Rebar (#3 at 18" on center both ways) is overkill for most patios but provides the best crack control.
A 4-inch slab is standard for patio use with foot traffic and furniture. If you're placing heavy items like a hot tub (2,000–5,000 lbs when full), increase to 6 inches and add reinforcement. Always use a compacted gravel base.
A basic broom-finish patio costs $6–$12 per square foot installed. Stamped or decorative concrete runs $12–$25 per square foot. A 200 sq ft patio typically costs $1,200–$2,400 for basic or $2,400–$5,000 for decorative.
Most jurisdictions require a permit if the patio is attached to the house, exceeds a certain size (often 200+ sq ft), or involves electrical or plumbing for outdoor kitchens. Check your local building department.
Yes, 2–4 inches of compacted gravel provides drainage and prevents the slab from settling unevenly. In expansive clay soils, 4–6 inches of gravel is recommended. Compact each lift thoroughly.
Light foot traffic is safe after 24–48 hours. Wait 3–7 days for furniture placement. For heavy items like hot tubs or fire pits, wait the full 28-day cure period for maximum strength.
Yes, you can pour in sections using construction joints (a form board between sections). Each section should ideally be poured to completion in one session. Sections should be planned at natural break points and control joint locations.