Concrete Floor Calculator

e.g. 12 identical pier footings, or 1 slab.
Slab/footing/wall/curb length, or column side.
Covers subgrade irregularity, spillage and over-excavation. 5-10% is normal for a formed pour on a prepared base.
Yields are from the QUIKRETE Concrete Mix No. 1101 data sheet (0.0075 cu ft of concrete per pound of dry mix).
Use the yield printed on your own bag if it differs (fast-setting, high-strength and crack-resistant mixes vary).
ASCE/SEI 7 Table C3.1-1a: 150 lb/ft3 reinforced stone concrete, 144 lb/ft3 plain. Lightweight mixes run 90-120. In metric those are 2400 and 2300 kg/m3.
Normalweight concrete is 150 lb/ft3 or, equivalently, about 2400 kg/m3.
Only needed if you are batching from separate cement, sand and stone rather than buying concrete.
Dry loose ingredient volume needed per unit of placed wet concrete. 1.52-1.57 is standard practice.
Mass of mixing water per unit mass of cement. ACI 318-19 Table 19.3.2.1 caps w/cm at 0.50 for concrete exposed to freezing and thawing or to de-icing chemicals. Set 0 to skip the water figure.
Used only to turn the batched sand volume into a weight. 100 lb/ft3 is the US EPA table figure for dry sand; use your supplier ticket when you have one.
US EPA table figure for crushed stone is 100 lb/ft3.
Use this instead of the price per cubic yard where concrete is sold by the cubic metre.
Flat charge the supplier adds per delivery, on top of the concrete itself.
Orders under this size attract the short-load fee below. Leave at 0 if your supplier does not charge one.
Quoted rate for forming, placing and finishing, applied to the finished surface area. Ask your contractor; rates are local.
Volume
4.9383 yd3
Concrete Calculator
Volume
133.333 ft3
Volume
3.7756 m3
Volume including waste allowance
146.667 ft3
Order this much ready-mix
5.4321 yd3
Rounded up to the quarter yard
5.50 yd3
Bags needed
245
Total weight of dry bags
19,600 lb
Weight of the finished concrete
20,000 lb
Weight of the finished concrete
10.000 ton (US short)
Weight of the finished concrete
9,071.8 kg
Weight of the finished concrete
9.072 t (metric)
Ready-mix truck loads
1
Finished surface area
400.00 ft2
Delivery and short-load fees
0.00 USD
Volume per element
133.3333 ft3
Worked out from QUIKRETE Concrete Mix No. 1101 Technical Data Sheet (bag yields, ASTM C138 density) and 6 other sources.
Footing, wall and column dimensions must come from a design by a qualified engineer or from a prescriptive table in the code adopted locally (e.g. IRC Table R403.1). This tool quantifies concrete for dimensions you supply; it does not size structural elements.

How this is worked out

5 steps
  1. slab: 20 ft x 20 ft x 0.3333 ft
  2. Volume = 133.3333 cu ft = 4.9383 cu yd = 3.7756 m3
  3. Adding 10% waste: 146.6667 cu ft = 5.4321 cu yd (order 5.5 cu yd)
  4. Bags: 146.6667 cu ft / 0.6 cu ft per 80 lb bag = 244.44 -> 245 bags
  5. Weight: 133.3333 cu ft x 150 lb/ft3 = 20000 lb

Results are general information, not financial, tax, legal, medical or engineering advice.