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Concrete Slab Calculator · Free calculator

12x16 Concrete Slab Calculator

A 12' × 16' slab covers 192 sq ft. At 4" thick that's 2.61 cubic yards of concrete with 10% waste — order 2.75 yd³ of ready-mix or 118 × 80 lb bags. Garage and RV pads at 6" need 3.91 yd³. Rebar, forms and base are worked out below.

Quick answer

4" slab (patio / shed)
2.61 yd³
80 lb bags @ 4"
118
6" slab (garage / RV)
3.91 yd³
Rebar #4 @ 18" OC
14 × 20' sticks
2x4 forms
4 × 16' boards
Est. cost @ 4" (ready-mix)
$454

▍Concrete Calculator

ft
in
ft
in
in
Waste Factor
$
L = 16' 0"W = 12' 0"D = 4"
Cubic Yards
2.61yd³
incl. 10% waste · Ready-mix truck: order 2.75 yd³
Cubic Feet
70.40ft³
Area
192.0sq ft
Weight
5.28tons
Weight
10,560lbs
Concrete bags needed
  • 80 lb bag (0.6 ft³ yield)118
  • 60 lb bag (0.45 ft³ yield)157
  • 40 lb bag (0.3 ft³ yield)235

Concrete for a 12x16 slab by thickness

192 sq ft, 10% waste included. Ready-mix ~$165/yd³ ordered in ¼ yd steps; 80 lb bags ~$6.50.

ThicknessTypical useCubic yardsOrder80 lb bags60 lb bagsWeightReady-mix80 lb bags $
4"Patio / Shed / Walkway2.61 yd³2.75 yd³1181575.28 tons$454$767
5"Driveway / Hot tub pad3.26 yd³3.50 yd³1471966.60 tons$578$956
6"Garage / RV Pad3.91 yd³4.00 yd³1762357.92 tons$660$1,144

Rebar grid for a 12x16 slab — 18" on center both ways

3" edge cover, no lap splices needed, 5% cut-off waste.

ItemQuantityNotes
Bars running the 16' way8 bars15' 6" each
Bars running the 12' way11 bars11' 6" each
Total rebar251 LFincl. laps
20 ft sticks to buy14+5% cut-off waste
Weight #3 / #494 / 167 lbs0.376 / 0.668 lb per ft
Wire ties88one per intersection
Rebar chairs (2"–3")24~36" grid
Alt: 6x6 welded wire mesh5 sheets5' × 10' sheets, 6" laps

Forms & site prep for 12x16

ItemQuantityNotes
Form perimeter56 LF2 × (12' + 16')
2x4 form boards (16 ft)4use 2x6 for 5"–6" slabs
Wood stakes (18"–24")24every 3 ft + each corner
Duplex nails482 per stake
Gravel base 4" (compacted)2.73 yd³ / 3.82 tons+15% for compaction
6-mil vapor barrier211 sq ft+10% for laps
Control joints28 LF2 cuts, panels ≤ 10'

How the math works

  1. Area: 16 ft × 12 ft = 192 sq ft
  2. Thickness in feet: 4" ÷ 12 = 0.333 ft
  3. Volume: 192 × 0.333 = 64.00 cu ft
  4. Add 10% waste: 64.00 × 1.10 = 70.40 cu ft
  5. Cubic yards: 70.40 ÷ 27 = 2.61 yd³ → order 2.75 yd³
  6. 80 lb bags: 70.40 ÷ 0.60 = 118 bags (60 lb: ÷ 0.45 = 157)
  7. Rebar: 8 bars × 15' 6" + 11 bars × 11' 6" = 251 LF → 14 sticks

Bag yields: 80 lb ≈ 0.60 cu ft, 60 lb ≈ 0.45 cu ft, 40 lb ≈ 0.30 cu ft (Quikrete / Sakrete). 1 yd³ = 45 × 80 lb bags.

Trade pro tips

  • 2.75 yd³ is under most plants' 4-yard minimum — ask about the short-load fee before ordering ready-mix.
  • Order 5–10% extra. Subgrade is never perfectly flat, and running short mid-pour leaves a cold joint.
  • Compact 4" of gravel base and slope the forms ¼" per foot away from any structure.
  • Chair the rebar so it sits in the middle third of the slab — rebar lying on the dirt does nothing.
  • Cut control joints ¼ of the slab depth, no more than 2–3 × the thickness (in feet) apart, within 6–18 hours.

Frequently asked questions

How many yards of concrete do I need for a 12x16 slab?

With 10% waste: 4" thick = 2.61 yd³ (order 2.75), 5" = 3.26 yd³ (order 3.50), 6" = 3.91 yd³ (order 4.00). A 12x16 slab is 192 sq ft.

How many 80 lb bags of concrete for a 12x16 slab 4 inches thick?

118 bags of 80 lb concrete (0.60 cu ft each) or 157 bags of 60 lb, including 10% waste. That is about 9,440 lbs of bags to haul.

How much rebar do I need for a 12x16 slab?

A grid at 18" on center both ways uses 8 bars running 16 ft and 11 bars running 12 ft — about 251 linear feet, or 14 twenty-foot sticks of #3 or #4 rebar, 88 ties and ~24 chairs.

How much does a 12x16 concrete slab cost?

Material only at 4": about $454 in ready-mix or $767 in 80 lb bags; at 6": about $660 ready-mix. Installed, 12x16 slabs typically run $6–$12 per sq ft ($1,152–$2,304) depending on region, access and finish.