Slab Rebar and Mesh Calculator

Bars each way, sticks to buy, chairs and tie points for a rebar grid, or wire mesh sheets.

Project Details
Enter your measurements and requirements
Results
Calculated estimates for your project
Bars each way8 long, 14 across
Sticks to buy22
Total length317 ft (212 lb)
Lap at splices20 in
Chairs15
Tie points112
Or: wire mesh, 5 x 10 ft sheets6

Turn these numbers into a build plan.

  • 22 bars
  • 22 sticks
  • $282 est. cost
Materials List
Recommended materials and quantities
#4 rebar, 20 ft22

Show your build

Finished the slab rebar and mesh? Snap a before and after. The photo maker lines them up into one image you can post, and a free Blueprint account keeps the photos with your measurements and materials.

Make a before and after
Project plan · built from your numbers

Rebar grid, 20 x 12 ft slab

#4 rebar at 18 in each way: 22 sticks, 15 chairs and tie wire.

Materials
$282
Time
1 day
Level
Intermediate
5 steps 4 tools 3 materials
  1. 1

    Confirm the design

    Check spacing and permit needs with your building department before ordering.

    • Design confirmed
  2. 2

    Cut the bars

    Cut 8 long bars and 14 cross bars, 3 in short of the forms at each end.

    • Bars cut
  3. 3

    Lay the grid

    Lay out bars at 18 in each way, lapping 20 in at splices.

    • Spacing checked
01 · Your numbers
Bars
22
Sticks
22
Est. cost
$282
02 · The plan

5 steps · 4 tools · 3 materials

2 more steps, the full tool list and a shopping list you can check off as you go.

03 · Finished

Your plan is 60% built. Save it.

3/5

Rebar grid, 20 x 12 ft slab

Finished in 1 day · $282 DIY

Built for your bars of 22. Your first plan saves free. No card needed.

Or save it with just your email

We send a link; open it and this plan is your first project. Your first plan saves free. No card needed.

Borrow these 4 tools from neighbors

How to calculate rebar for a slab

Rebar stops about 3 in short of the edges so concrete covers the steel.

  1. Subtract the cover. Take 6 in off each dimension for 3 in of cover at both edges.
  2. Count bars. Divide the other dimension by the spacing, round down and add one.
  3. Add laps. Splice long runs with a lap of 40 bar diameters.
  4. Convert to sticks. Split bars across 20 ft sticks and reuse cutoffs where you can.
  5. Add chairs and ties. A chair about every 4 ft holds the mat at mid-depth.

Rebar for a 20 x 20 ft slab

SpacingTotal bars20 ft sticksLinear feet
12 in4040780
16 in3030585
18 in2828546
24 in2020390

Pour volume is in the concrete slab calculator; footings are in the footing rebar calculator.

Frequently asked questions

What rebar spacing for a 4 in slab?

#3 or #4 at 18 to 24 in each way is common for patios and sheds. A permit or engineered design takes priority where one applies.

Rebar or wire mesh?

Rebar gives more strength and stays in position better. Mesh is fine for light crack control but must be held up in the slab.

How much should rebar overlap?

A common rule is 40 bar diameters, which is 20 in for #4. Follow your plans if they say otherwise.

How high should rebar sit?

Around the middle of a thin slab, on chairs. Bars on the ground do little.

How many ties do I need?

Most DIY grids tie every other intersection. The calculator shows every intersection as a maximum.

Related calculators

All calculators

Concrete Slab Calculator

Draw any slab shape and get a full materials list, tools, cost, and step-by-step plan

Footing Rebar Calculator

Rebar count, lap splices and weight for continuous footings

Concrete Calculator

Cubic yards, bags and cost for slabs, footings, walls, columns, stairs and curbs

Related cheat sheets

All cheat sheets

Concrete Cheat Sheet

Curing calculator with walk and drive-on dates, strength chart by temperature, mix ratios by PSI, bags per yard, control joints and weather rules

Masonry Joint Type Visual Guide

Visual reference illustrating common mortar joints and weather resistance advice

Retaining Wall Guide

Block selection, base preparation, drainage requirements, and height limitations

Plan the whole project

Turn these numbers into a full project plan

DIYProject.ai turns your measurements into an ordered task list, a complete materials list, and a priced shopping cart, then tracks your spend as you build. The calculators and cheat sheets stay free, no account required.

Get your free planPlan any project with AI