Before going to build any RCC structure we need to calculate steel quantity for purchasing.

We only have drawings. So, we need to calculate steel quantity from drawings.

There is no easy formula for calculating steel quantity.

But the basic thing is simple.

## The Basic Formula For Calculating Steel Quantity

No matter what type of structure you are going to calculate steel quantity for, the basic thing is the same.

You need to go through these three steps.

### 1.Getting The Number Of Steel Bars:

You first need to count the total number steel bars from the drawing.

While counting, get the number of same size bars.

Suppose, the drawing of a structure has both **10mm **and **12mm **diameter bar, you need to count both sizes of bars separately.

Another thing you need to keep in mind is that you’ll have different length of bars in your drawing. So count the same length bars together.

For example, you have both **10 **feet and **12 **feet long bars in your drawing. So count the **10 **feet long bars and **12 **feet long bars separately.

### 2. Get The Length Of Bars

Get the length of a bar from the drawing and multiply the length with the number of bars you counted in step #1.

Once you multiply, you’ll get the total length of same size bars.

### 3. Get The Weight Of Bars

Steel bars are available in the market as weight like **kilogram **or **Ton**.

So you need to convert the length of the bars into the weight.

For calculating the weight of bars, you need to know the unit weight of different size of bars. I’ve talked about how to calculate the unit weight of steel bars before.

Simple!

Isn’t it?

## How To Calculate The Steel Quantity From Drawings?

As I shared most of the things related to buildings, I’ll discuss calculating steel quantity for different parts of a building.

But, you can calculate steel quantity for any type of structure applying this technique.

A building has different structural parts. Such as footing, column, beam, slab, and lintel-sunshade, etc.

So, I’ll discuss how to calculate steel quantity for these structural parts of a building from drawing.

### How To Calculate Steel Quantity For Footing From Drawings?

You’ll have a structural drawings for footing which will be as image below.

#### 1. Get The Number Of Steel Bars:

- 16 mmØ bar

**Number of bars** = {(width of footing – 2 × clear cover) ÷ Spacing of bars} + 1

= {(4′ – 2 × 3″) ÷ 4″} + 1

= {3½’ ÷ 4″} + 1

= 11.60 nos

Say, **12 nos**.

- 20 mmØ bar

**Number of bars** = {(length of footing – 2 × clear cover) ÷ Spacing of bars} + 1

= {(6′ – 2 × 3″) ÷ 4″} + 1

= {5½’ ÷ 4″} + 1

= 17.66 nos

Say, **18 nos**.

#### 2. Get The Length Of Bars

- 16mmØ bar

**Length of a bar** = Length of footing – 2 × clear cover + 2 × end hook

= 6′ – 2 × 3″ + 2 × 6″

= 6½’.

**Total length of 16mmØ bar** = number of bars × length of a bar

= 12 x 6½’

= **78 feet**

- 20mmØ bar

**Length of a bar** = width of footing – 2 × clear cover + 2 × end hook

= 4′ – 2 × 3″ + 2 × 6″

= 4½’.

**Total length of 20mmØ bar** = number of bars × length of a bar

= 18 x 4½’

= **81 feet**

#### 3. Calculating The Weight Of Steel Bars

**Weight of steel bars** = Length of bars × unit weight

- Weight of 16mmØ bar

= 78′ × 0.48

= 37.44 kilogram

Say, **38 kilogram**.

- Weight of 20mmØ bar

= 81′ × 0.75

= 60.75 kilogram

Say, **61 kilogram**.

You may need **10mmØ **bars to bind the footing net all around. Calculate these as you require.

### How To Calculate The Steel Quantity From Drawing For Neck Column

In the above drawing, the column has **three **sizes of bars.**20mmØ **and **25mmØ **bar as main reinforcement and **10mmØ **bar as stirrups.

#### 1.Getting Number Of Bars

- 20mmØ

**Number of bars** = 6 (specified in drawing).

- 25mmØ

**Number of bars** = 4 (specified in drawing).

- 10mmØ

**Number of stirrups** = (Clean height of column ÷ spacing of stirrups) + 1

Getting the clear height of columns is a little bit tricky.

You need to study the footing drawing carefully.

Sometimes there is a note in the footing drawing that how depth the footing should be placed below the ground.

From there, you’ll get the clear height of neck columns.

For the clear height of floor columns, you need to depend on the architectural drawing.

There should be a cross sectional plan in architectural drawing book.

From there you’ll get the clear height of floor columns.

Let’s assume, the clear height of the column we are calculating steel for is **8 **feet.

But, when you calculate steel quantity for neck/short column you need to add the **thickness of footing** with the clear height.

In that case the height of the column will be,

= Clear height of column + thickness of footing.

So, **number of stirrups for neck column** is,

= (Clear height of column + thickness of footing) ÷ spacing of stirrups

= {(8′ + 1′) ÷ 4″} + 1

= 28.27

Say, 29 nos.

We also need to use at least **two numbers** of stirrups in the **beam-column joint**. It’s sometimes recommended in the general notes of structural drawing.

So, total required number of stirrups are,

=29 + 2

= **32 nos**.

#### 2. Get The Length Of Bars

**Length of a bar** ( for neck column)= clear height of column + thickness of 1st-floor beam + lapping for future column + thickness of grade beam + depth of footing + thickness of footing + end hook.

- 20mmØ

length of a 20mmØ bar,

= 8′ + 1′ + 60D + 1′ + 3′ + 1′ + 1½’

[*Lap length of columns is normally calculated as 60D. However, you’ll get notes about this in structural drawings. You should follow that*.]

= 15½’ +60D

= 15½’ +60 × ¾” (20mm = ¾”)

=15½’ + 45”

= 19.25 feet.

As we have 6 numbers of bars, so the total length of 20mmØ bars is,

=6 × 19.25

= **115.5 feet**

- 25 mmØ

Length of a 25mmØ bar is,

= 15½’ +60D (see how we calculated the length of a 20mmØ bar)

= 15½’ +60 × 1” (25mm=1”)

= 15½’ +60”

= 20½ feet.

Total length of 25 mmØ bars

= 4 × 20½ (We have 4 numbers of 25mmØ bar in our drawing).

= **82 feet**.

- 10mmØ bar as strirrups

**Length of a bar of a stirrup** = 2 × (Legnth of column + width of column) – 4 × clear cover + 2 × hook

= 2 × (43” + 23”) – 4 × 3” + 2 × 3”

= 2 × 66” – 12” + 6”

= 132” – 12” + 6”

=126”

=10½’

The total length of bars for stirrups,

= 32 × 10½’ (Numbers of stirrups, we calculated above, are 32 nos)

= **336**‘

#### 3. Calculating The Weight Of Steel Bars

**Weight of steel bars** = Length of bars × unit weight

- 20 mmØ bar

= 115.5× 0.75

=**73.12 **kilogram.

- 25 mmØ bar

= 70 × 1.17

=**81.90 **kilogram.

- 10 mm bar

= 336‘ × 0.19

=**63.84 **kilogram.

### How To Calculate The Steel Quantity For Beam From Drawing

#### 1.Getting Number Of Bars

- 20 mmØ dia bar

Number of **20mmØ **longitudinal bars in top and bottom,

=3 + 3

=**6 nos**.

Number of 20 mmØ extra top bar on support1 =** 2 nos**.

Number of 20 mmØ extra top bar on support2 =** 2 nos**.

Number of 20 mmØ extra bottom bars = **2 nos**

- 10 mmØ bar

Number of stirrups for 1st span,

= (22′-8″)/4″ +1 = 69 + 1 = 70 nos.

Number of stirrups for 2nd span,

= (8′-4″)/4″ + 1 = 25 + 1 = 26 nos.

Total number of stirrups = 70 + 26

= **96 nos**.

#### 2. Get The Length Of Bars

- 20mmØ bar

**Length of a longitudinal bar** = Beam length – 2 × clear cover + 2 × end hook + lap length (if required)

= 36’ – 2 × 1½” + 2 × 12D (Lap length isn’t required here as we don’t need more than a full-length bar. D=20mm=¾”)

= 36’ – 3” + 18”

=37.25 feet

Total length of 20mmØ longitidinal bars,

= 6 × 37.25

=**223.50 feet**.

**Length of a 20 mmØ extra top bar on support1**,

= Extended length from support + width of support – clear cover + end hook (if the bar on end support)

= (7′-5″) + 20″ – 1½” + 9½”

= 9.75 feet

Total length of extra top bars on support1,

= 2 × 9.75

= **19.5 feet**

**Length of a 20 mmØ extra top bar on support2**,

=(7′-5″) + (11′-8″) – 1½” + 9½”

=19.75 feet

Total length of extra top bars on support2,

= 2 × 19.75

= **39.5 feet**

**Length of a 20 mmØ extra bottom bar**

=Distance between supports – 2 × distance between extra bottom bar and nearest support

=(22′-8″) – 2 × (2′-10″)

= 17 feet

The total length of the extra bottom bar,

= 2 × 17′ (there are 2 bars for Eb shown in the image above)

= **34 feet**.

So, The total length of 20mm bars in the beam is,

=223.5 + 19.5 + 39.5 + 34

= **316.50 feet**.

- 10mmØ bar as strirrups

**Length of a bar of stirrup**,

= 2 × (height of beam + width of beam) – 4 × clear cover + 2 × hook

= 2 × (24” + 12”) – 4 × 1½” + 2 × 3”

= 2 × 36” – 6” + 6”

= 72”

=6 feet.

**The total length of bars for stirrups,** = 96 × 6’ (Numbers of stirrups, we calculated above, are 96 nos)

=

**576 feet**.

#### 3. Calculating The Weight Of Bars

**Weight of steel bars** = Length of bars × unit weight

- 20 mmØ bar

= 316.50 × 0.75

=**237.37 kilogram**.

- 10 mmØ bar

= 576 × 0.19

=**109.44 kilogram**.

### How To Calculate The Steel Quantity Of Slab From Drawing

Different types of reinforcement are designed for different types of slab.

So calculating steel quantity of slab varies depending on the reinforcement design.

I’ll show you the process of calculating steel for a double reinforced slab.

#### 1.Getting Number Of Bars

**Numbers of bars** =( length/width of slab ÷ spacing of reinforcement)+1

- 10mmØ bar

**1- 10mmØ 5″ c/c bottom and top**

Number of bars ={ (9′-9″) ÷ 5″}+1

= 24.21 nos.

Say, 25 nos.

As this reinforcement will be used in both the top and bottom, so the number of bars,

= 25 × 2

= **50 Nos**.

**2- 10mmØ 6″ c/c bottom and top**

Number of bars ={ (15′-4″) ÷ 6″}+1

= 31.66 nos.

Say, 32 nos.

As this reinforcement will be used in both top and bottom, so the number of bars,

= 32 × 2

= **64 Nos**.

#### 2. Get The Length Of Bars

You can take the length or width of slab as a length of a bar.

- 10mmØ bar

**1- 10mmØ bar 5″ c/c bottom and top**

Length of a bar is,

= 9′-9″

=9.75 feet.

The total length of bars = number of bars × length of a bar

= 50 × 9.75

= **487.50 feet**

**2- 10mmØ bar 6″ c/c bottom and top**

length of a bar is,

= 15′-4″

=15.33 feet.

The total length of bars = number of bars × length of a bar

= 64 × 15.33

= **981.12 feet**

**Total length of 10 mmØ bars is**,

= 487.50+981.12

=**1468.62 feet**.

#### 3. Calculating The Weight Of Bars

**Weight of steel bars **= Length of bars × unit weight

- 10 mmØ bar

= 1468.62 × 0.19

=**279.04 kilogram**.

**Conclusion**

You may have noticed that I sometimes didn’t consider the clear cover, bend deduction length, etc. in the above steel calculation.

That’s because we calculate steel quantity mainly for purchasing the steel. So, that minor length due to clear cover, etc. don’t have a big impact. So can ignore this.

But before purchasing steel bars, don’t forget to add **10% extra** quantity for wastage.

Calculating steel quantity from drawing isn’t that hard task if you understand structural drawings.

The thing is simple.

You just need to get the total length of same size bars. Then convert that length into the weight.

*Your Opinion**Is there any easiest way to calculate steel quantity from drawings? Please share in the comments below…*

mrhotmaster says

Thank You For This Article!

It is very enjoyable & Useful

Liton Biswas says

You’re welcome.