Concrete Slab Wizard

Draw your slab, answer a few questions, and get a complete materials list, tool list, cost estimate, and step-by-step plan.

1. Draw your slab
Drag on the grid to draw. Snap shapes together, weld them into one slab, and hover a shape to add a connected piece with the +.

Add shape

Layers

0'5'10'15'20'25'0'5'10'15'12' × 12'
2 ft
grid = 1' · shift = square / lock ratio · space-drag to pan control joints

Selected shape

Select a shape to edit its size, snap it to others, or weld it into one slab.

Arrows nudge · ⌫ delete · ⌘C / ⌘V copy & paste

2. Answer a few questions
Tell us what the slab is for and we'll suggest a thickness, base, strength, and reinforcement — override anything.

Furniture and foot traffic. Wire mesh keeps it flat.

Suggested 4"
Sold by the cubic yard; short-load fees apply under ~5 yd.

Vapor barrier

6-mil poly under interior / enclosed slabs

Include tool rental in total

Add advisory rental/buy estimates to the grand total

Extra concrete for spillage and uneven subgrade. 10% is typical.

3. Your plan
Materials, tools, cost, and a step-by-step build plan. Every unit price is editable.

Concrete

1.96 yd³

Footprint

144 ft²

Perimeter

48 ft

Concrete$330

Ready-mix concrete (3000 psi)

2 cu yd · Ordered by the cubic yard, delivered. Short-load fees apply under ~5 yd.

Alt: Bagged: 88 x 80 lb bags

$330

Base & membrane$88

Compactable gravel base (4")

2.5 tons · 1.78 cu yd of crushed stone / road base, compacted in lifts.

Alt: Recycled concrete aggregate (often cheaper by the ton)

$88

Reinforcement$67

Welded wire mesh (6x6 W1.4)

7 sheets · Flat sheets lay flatter than rolled mesh. Overlap one square.

Alt: Rebar #3 grid (see rebar option)

$63

Mesh chairs / raisers

12 each · Keep mesh off the subgrade, in the slab's middle.

$4

Forms$100

Form boards (2x4)

7 8 ft boards · ~48 linear ft of edge form around the slab.

Alt: Reusable metal forms (rent) for large/curved pours

$42

Form stakes

28 each · One every ~2 ft plus corners. Wood or steel.

$49

Form screws

1 box · Screws (not nails) make stripping forms painless.

$9

Finishing$10

Expansion / isolation strip

2 8 ft strips · Where the slab meets a house, footing, or existing slab.

$10

Materials$595
Tool rentalnot in total$185
Estimated total$595

From US average prices — click any price to match a local quote. Excludes delivery, permits, and labor.

Tools you'll need

  • WheelbarrowMove and place the concrete.
  • Screed board (straight 2x4)Longer than the form is wide.
  • Plate compactorrent ~$70/dayCompact the gravel base in 2" lifts.
  • Bull floatrent ~$55/dayFlatten and close the surface after screeding.
  • Magnesium hand floatDetail work and edges.
  • EdgerRounds and strengthens the slab perimeter.
  • GrooverTools control joints into the wet slab.
  • Shovel, steel rake & margin trowelSpread, pull, and detail the pour.
  • Gloves, eye protection & rubber bootsWet concrete is caustic — cover up.
  • Concrete saw + diamond bladerent ~$60/dayOnly if you cut control joints the next day instead of tooling them wet.

Rental prices show only for specialty gear — skip them if you already own it.

Step-by-step plan

Your build, tracked

Save this plan to Blueprint

Turn your slab into a project with the full step-by-step plan, tool list, and shopping list you can check off as you build — about $595 in materials.

About the concrete slab calculator

Overview

Most slab calculators ask for one length and one width. Real slabs are rarely a plain rectangle: patios wrap around corners, garage pads have notches, and driveways flare at the apron. This tool lets you draw the actual footprint — rectangles, L-shapes, curves, and cutouts — then computes the exact concrete volume, gravel base, reinforcement, form lumber, tools, and a step-by-step pour plan.

Pick what the slab is for and it suggests a code-typical thickness, base depth, strength, and rebar grid, all of which you can override. Every material quantity is deterministic (no guessing), and every unit price is editable so the cost estimate matches your local supplier. When you like the plan, save it to a Blueprint project to track the build.

How to use this tool
  1. Drag on the grid to draw your slab, or add rectangle, semicircle, quarter-round, and triangle shapes and butt them together for L, T, or U shapes.
  2. Click any shape to set its exact width, length, and position, or to rotate curved shapes.
  3. Choose the slab's purpose — it sets a suggested thickness, gravel base, strength, and rebar grid you can override.
  4. Add optional structural elements (stairs, columns, footings) if your pour includes them.
  5. Review the materials, tools, and cost, adjusting any unit price to a local quote, then follow the step-by-step plan or save it to Blueprint.
Frequently asked questions