Concrete calculator: How to calculate concrete?

There’re many types of concrete and grades of concrete (e.g. Ready mix, Precast, Reinforced conc). In Calculation of concrete, first of all Multiply Length and Width & Hight to get Volume. It is same as Plaster/mortar calculation.

Let suppose a slab of single story house which has 50 feet length and 25 feet width.

Concrete slab calculator:

Length= 50 ft

Width= 25 ft

Area of slab = L×W

Area of slab = 50’×25′ = 1250 sft or 138.9 sqyd

Thickness of slab = 6 inch = 0.5 ft (That commonly used)

Wet Volume of Concrete = Area × Thickness of slab

Wet Volume=1250×(6/12) = 625 Cft

  • 6 divided by 12 to convert inch into foot

Dry Volume of concrete = 625×1.54= 962.5 Cft or 27.25 cu.m (35.31cft = 1 cu.m)

“It is compulsory to multiply with 1.54, to convert wet volume of concrete into dry volume (because addition & evaporation of water cause shrinkage in concrete mix, which ultimately decrease in volume).”

Dry volume means you need 962.5 Cft concrete for 25’x50′ slab.

Concrete yard calculator: How to calculate yards of concrete?

There 3 most common types of concrete bags being used. E.g. 40-pound concrete bag has yield of 0.011 cubic yards, 60-pound concrete bag has yield of 0.0167 cubic yards, 80-pound concrete bag has yield of 0.222 cubic yards.

  1. Multiply dimensions in feet (L×B×H). =25×50×0.5 =625 cft
  2. Multiply with 1.54 (to convert into dry volume). =962.5 cft
  3. Divide by 27 to convert into Cubic Yards. =35.64 cubic yards
  4. For 40-pound concrete bag, 35.64/0.011 = 3210 bags.
  5. 60-pound concrete bag, 35.64/0.0167 = 2138 bags.
  6. For 80-pound concrete bag, 35.64/0.0222 = 1610 bags.

Concrete bag calculator: How many bags of concrete do i need calculator?

There are 3 types of commonly used concrete bags. Concrete mix yield increase about 0.15 about every 20 pound increment in concrete bag. E.g. 40-pound concrete bag yield is 0.30 cubic feet, 60-pound concrete bag yield is 0.45 cubic feet, 80-pound concrete bag yield is 0.60 cubic feet.

If you need 962.5 cft concrete. Simply divide total volume of concrete by the yield of concrete bag. e.g.

  1. For 40-pound concrete bag, 962.5/0.30 = 3208 bags.
  2. 60-pound concrete bag, 962.5/0.45 = 2138 bags.
  3. For 80-pound concrete bag, 962.5/0.60 = 1604 bags.

Concrete cost calculator:

As quikrete concrete bags prices for 40-pound concrete bag is $2.68, 60-pound concrete bag is $3.58 and 80-pound concrete bag is $4.48.

  1. For 40-pound 3208×2.68 = $8597.44
  2. 60-pound 2138×3.58 = $7654.04
  3. For 80-pound 1604×4.48 = $7185.92
concrete calculation, Concrete calculator: How to calculate concrete
Concrete calculation

How to calculate concrete:

Now we will use dry volume in concrete calculation to get Quantity of Cement, Sand & Aggregate for 1:2:4 concrete mix calculation.

Ratio of concrete mix (Grade M15) = 1:2:4

Sum of ratio = 7

Cement calculator for Concrete:

  1. Quantity of Cement = (1÷7)×962.5 = 137.5 Cft
  2. Cement = (1÷7)×27.25 = 3.9 Cum

Density of cement = 1440kg/m3 or 40.77kg/cft

  • Multiply cft with 40.77 & cum with 1440 to get quantity of cement in KGs.

Cft>>> 137.5×40.77= 5606 Kg

Cum>>> 3.9×1440= 5606 kg

How to calculate cement bags in concrete? To find cement Bags divide by 50 (50 kg in one bag of cement).

5606/50 = 112 bags of cement

Or directly calculate cement bags from Volume:

Volume of cement bag= 0.034cum or 1.226cft

Cft>>> 137.5÷1.226 = 112 Bags

Read also Plaster/mortar calculation.

Sand calculator in Concrete:

  1. Quantity of Sand = (2÷7)×962.5 = 275 Cft
  2. Sand = (2÷7)×27.25 = 7.78 Cu.m

Density of sand is 1600kg/m3 OR 45.30 kg/cft

Read also Brick calculation.

Aggregate calculator in Concrete:

  1. Quantity of Aggregate = (4÷7)×962.5 = 550Cft
  2. Aggregate = (4÷7)×27.25 = 15.57 Cu.m

Calculation of Water Cement Ratio in concrete:

  1. Water cement ratio means quantity of water against cement (in kgs).
  2. W-C Ratio = 50% × Quantity of cement (kg)
  3. Water= 5606×0.50 = 2803 liters.

50% of water quantity is commonly used in ordinary concrete mix , but it can be b/w 22% to 50%.

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