In this article, we will discuss the **concrete calculation**, and you will learn **how much concrete do you need** and **concrete yard calculation?**

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.

## Concrete slab calculation:

Let suppose a slab of single story house which has **50 fee**t length and **25 feet** width and 6″ thickness.

**Area of slab = L×W**- Area of slab = 50’×25′ =
**1250**sft or**138.9 sqyd** **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 calculation:

#### 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 **0.0222 cubic yards**.

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

### Concrete bag calculation:

#### How many concrete bags do i need?

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.

- For
**40-pound**concrete bag, 962.5/0.30 =**3208****bags**. **60-pound**concrete bag, 962.5/0.45 =**2138 bags**.- 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**.

- For
**40-pound**3208×2.68 =**$8597.44** **60-pound**2138×3.58 =**$7654.04**- For
**80-pound**1604×4.48 =**$7185.92**

### How to calculate crushed concrete:

Now we will use dry volume of **25×50×0.5 =962.5** in crushed concrete calculation to get quantity of cement, sand & aggregate for 1:2:4 concrete mix.

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

**Sum of ratio = 7**

### Cement calculation for Concrete:

**Quantity of****cement for area**Cft**25×50×0.5**(×1.52) = (1÷7)×962.5 = 137.5**Cement = (1÷7)×27.25 = 3.9**Cum

Density of cement = **1440kg/m ^{3}** 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 calculation in Concrete:

**Quantity of****sand**Cft**25×50×0.5 (×1.52)**= (2÷7)×962.5 = 275**Sand = (2÷7)×27.25 = 7.78**Cu.m

**Density of sand is 1600kg/m ^{3} OR 45.30 kg/cft**

Read also Brick calculation.

### Crush calculation in Concrete:

**Quantity of****crush for**Cft**25×50×0.5 (×1.52)**= (4÷7)×962.5 = 550- To convert in cubic yard divide 550 by 27 =
**20.3 cubic yards**. - Convert in kgs multiply 20.3 with 764.5 =
**15562 kgs**. - To convert into tons just divide with 1000=
**15.5 tons**. **crush = (4÷7)×27.25 = 15.57**Cu.m

### Calculation of *Water Cement Ratio* in concrete:

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

50% of water quantity is commonly used in ordinary concrete mix , but it can be b/w 27% to 50% for designed mix concrete.

### Concrete pier size calculator:

The simple rule for concrete pier size calculation is to add **1 inch** in diameter of pier against **1 foot** of span. **6 feet** of span can stand on **6″** diameter of pier, 8′ can stand on 8″, 10″ can stand on 10″. If the span is more than 12 feet just add one more pier in between.