How-much-does-#8-rebar-weight-per-foot

I have been asked by one of our fan a question that how much does #8 rebar weight per foot ? So I thought why not create a comprehensive guide on unit weight of deformed rebars. So if you have any question about:-

  • weight of rebar per foot
  • steel weight calculation formula
  • weight of reinforcing bars
  • unit weight of steel

You are at the right place then because I am going to explain everything related to unit weight.

Reinforcement bars are estimated, procured and paid by unit of weight i.e. in kilograms, pounds, tonnes etc. By unit weight of deformed rebars we mean its weight per unit length. The two common units used for recording unit weight of steel are kilogram per meter (kg/m) and pounds per feet (lb/ft).

Here’s a table showing unit weight of reinforcing steel bars in kg/m;

Bar No. Size (diameter) mm Theoretical weight (kg/m)
#3 9.53 mm 0.56
#4 12.70 mm 1.00
#5 19.05 mm 1.56
#6 25.40 mm 2.24
#7 32.26 mm 3.05
#8 35.81 mm 3.98
#9 28.65 mm 5.07
#10 32.26 mm 6.42
#11 35.81 mm 7.92
#12 38.10 mm 8.93
#14 43.00 mm 11.41
#16 50.80 mm 15.88
#18 57.33 mm 20.28
#20 63.50 mm 24.82

Following table shows unit weight of reinforcing bars in lb/ft:

Bar No. Size (diameter) in Theoretical weight (lb/ft)
#3 0.38 0.38
#4 0.50 0.67
#5 0.63 1.04
#6 0.75 1.50
#7 0.88 2.04
#8 1.00 2.67
#9 1.13 3.40
#10 1.27 4.30
#11 1.41 5.31
#12 1.50 5.99
#14 1.69 7.65
#16 2.00 10.65
#18 2.26 13.60
#20 2.50 16.63

In any construction project involving reinforcing bars, bar bending schedules are submitted by the Contractor as an estimate of the quantity of rebar mentioning the cut length of bar, diameter and weight of the rebar. These bar bending schedules are checked and verified by the Engineer at site for inclusion in IPC of the Contractor which is then paid by the Employer.

 

Steel Weight Calculation Formula

You might have heard or read about the formula as follows:

Unit weight of steel = d*d/162.28 (kg/m)

Although this formula gives you a very close approximation of the unit weight of rebar, but this will never give you the exact value of the steel unit weight.

So what to do?

You have to refer the steel manufacturer’s manual wherein the unit weight of the steel bars is quoted.

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How much does #8 rebar weight per foot

Derivation of Rebar Unit Weight Formula D2/162.28      

Unit weight of steel = D2 / 162.28

Now this formula has been derived from the density of the steel rebar which is 7850 Kg/m3.

D is the diameter of the rebar in mm.

The result of this formula would be weight per length i.e. kg per meter.

If we multiply the density (ρ) with the cross-section area of the rebar we will get the weight per length of rebar.

So;

Ρ x A = (7850 kg/m3 ) x (π x D2)/4

= (7850 kg/m3 ) x (3.14 x D2)/4

=6162.25 x D2 kg/m (where D is in meters)

Well, mostly we have φ diameter of rebar in millimeters.

So let’s say Dm is diameter in mm so in order to convert that into meters we have to divide it by 1000.

Thus;

1 meter = 1000 millimeters

=6162.25 x (Dm/1000)2 kg/m

=6162.25 x (Dm/1000)2 kg/m

=0.00616225 x Dm2

Or

= Dm2/(0.00616225)-1

=Dm2/162.2783 in kg/m

Where Dm is dia of rebar in mm.

So this formula is used for approximate value of unit weight of steel in MKS system.

Coming back to our main asked question.

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How much does #8 rebar weight per foot ?

How much does #8 rebar weight per foot? Now this needs weight per foot.

So we need to derive the formula for FPS system.

We know that

1 meters = 3.28084 feet

So ;

Ρ = 7850 kg/m3

Can be written as

Ρ = 7850 kg/(3.28084)3 feet

Ρ =222.287 kg /ft

Now;

Ρ x A = (222.287 kg/ft3 ) x (π x D2)/4

Ρ x A = (222.287 kg/ft3 ) x (3.14 x D2)/4   kg/feet

=174.495 D2  where D is in feet

As mostly we have dia of rebar in mm so to convert that in feet we need;

1 foot = 304.80 mm

Lets say Dm is dia in mm so

Using Dm/304.80 in above equation

=174.495 (Dm/304.8)2

=0.001878 Dm2

Or

= Dm2  / (0.001878)-1

=Dm2/533

Where  Dm is dia of rebar in mm.

Now we can answer the above question.

Answer [SOLUTION]

Φ = #8

Convert into mm

(now in our local language we call # as ‘sutar’)

So

1 sutar = 1/8 x 25 mm

Φ = #8/8 x 25.4 = 25 mm

So putting in above formula;

Unit weight of #8 rebar per foot =252/533 = 1.1726 kg / feet

So #8 rebar weight per foot comes out to be 1.1726.

Here are the unit weight of some commonly used diameter of rebar

 

# of rebar Nominal Diameter *
(mm)
Unit weight of rebar
Kg/m ** Kg/ft ***
#3 9.5 0.5561 0.1693
#4 12.7 0.9939 0.3026
#6 19 2.2246 0.6773
#8 25 3.8514 1.1726
#10 31.7 6.1923 1.8853
#11 36 7.9862 2.4315

So I have given a comprehensive answer to – How much does #8 rebar weight per foot – the question asked by one of my friend I hope you have liked the way of my explanation. If you have any question or problem please comment it below or contact us.

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Written by Saad Iqbal

He is a professional civil engineer with over 5+ years of work in mega construction projects. He's been on the internet community for quite some time now. He is a passionate blogger and a construction geek. You can get in touch with him via the contact us page.

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