How To Calculate Steel Quantity | Steel Quantity Formula | How to Calculate Steel Quantity from Drawing | BBS of Slab | Steel Quantity Calculation

How To Calculate Steel Quantity | Steel Quantity Formula | How to Calculate Steel Quantity from Drawing | BBS of Slab | Steel Quantity Calculation

Data requires for steel quantity calculation:

1) Plan of Section or Element. (Slab, Beam, Column &


2) Section and Elevation Details.

3) All dimensions must be clear and co-related.

Read More: Steel Quantity Calculation Excel Sheet

- The bars are required to be grouped together for each of the structural units, For e.g. beam, etc.

- In a building structure, the Listing of bars should be done floor to floor.

- For cutting and bending operations, schedules should be provided separately in the form of A4 sheets and should not a part of the detailed reinforcement drawings.

- The form of bar, fabric schedule, and the shapes of the bar used should be according to BS 8666.

- It is always preferable that bars should be listed in numerical order in the schedule for better understanding.

- The bar mark reference on the label which is attached to a bundle of bars refers seperately and uniquly to a specific group of defined length, size, shape, and type used on the job.

- This is very crucial as a bar mark reference can then state to a class of bar characteristics. Similarly, it also helpful in the case of steel fixers and laborers can keep track of the type and number of bars needed to complete a specific work.

slab section

Slab Section

How to Calculate Steel Quantity from Drawing

Slab Reinforcement Details

Let, us take one example of a slab for steel quantity calculation.

Following Steel Quantity, we have to calculate from drawing.

- Cement Concrete for Slab.

- Centering and Shuttering for Slab.

- Weight of 12mm dia. Bars.

- Weight of 8mm dia. Bars.

- Prepare Bar Bending Schedule.

(Note: Weight of Steel

bars 12mm — @ 0.9 kg / m

8 mm — @ 0.4 kg/m,

Sr. No.Item DescriptionNo.Length (m)WidthHeightQuantity1Cement Concrete for Slab (1:1.5:3):L = 4 + 0.23 + 0.23 = 4.46 m14.463.460.121.85 cu mB = 3 + 0.23 + 0.23 = 3.46

(See drawing in to in dimension (without the wall) of the slab is given 3 m x 4 m. For calculating Quantity of slab concrete we have to calculate out to out the dimension of the slab.)


Centering & Shuttering for Slab:





— 12.00

cu m







cu m

( Take 30mm Extra Above
Slab Thickness)






cu m



cu m

(Formwork Quantity is calculated in a square meter. There is one bottom portion and 4 side shuttering. For bottom we have in to in dimension of slab 3m x 4m. For Side formwork, there is 2 different dimensions, 2 with 4 m side and 2 with 3 m sides. For the total length we have to add wall width of both sides to get the total length.)

Read More: Estimation of a Building with Plan

Steel Quantity Formula

312 mm dia main Steel bars @ 150 mm c/c Alternate bent up. L = 3 + 0.23 + 0.23 + (2 x 9 x 0.012) — (2 x 0.05) L = 3.58 (Straight Length) (For finding out nos. of the bar we have to calculate the straight length of the main bar without adding extra length due to bent up) Span = 4 + 0.23 + 0.23 — (2 x 0.05)
= 4.36 m No. of Bars = (4.36/0.15) + 1
= 30 nos. Extra Length of Bent up:

How to calculate steel quantity from drawing

X — Value

Extra Length =

0.45 X X

= 0.12(Slab Thickness) — 2 x 0.02 (Top & Bottom Cover) — 0.012/2(Harf dia

top) — 0.012/2( Half dia bottom) X

= 0.12- 2 x 0.02–0.012/2–0.012/2 = 0.068 m L

= 3.58 + 0.45X
L = 3.58 + 0.45 x 0.068
3.6130 3.61 @0.90 97.47 kg

(In case

of bent up bars are provided on both sides, we have to add 0.45 X twice in



8 mm dia. Distribution steel @ 180 mm c/c


at Bottom:


Length = 9d
= 9 x 0.008
= 0.072



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Mike Mahajan

Mike Mahajan


Bhushan Mahajan who himself is a Civil Engineer by profession is also the main author and maintains the website himself.