Steel Weight Calculator

Unit weight, total weight and material cost for rebar (IS 1786 nominal mass, ≈ d²/162, or ASTM #3–#18), flat plate and round pipe.

Bar diameter, d (mm)

Length per piece, L (m)

Number of pieces, n

Price per kg — optional, any currency

Total steel weight

106.5 kg

= 0.107 t · 0.888 kg/m unit weight

Formula & substitution

w = (π /4) \times d^{2} \times 7850/1 0^{6} \approx d^{2} /162 (k g / m)

w = (π/4) × 12² × 7850 / 10⁶: 0.888 kg/m (d²/162 ≈ 0.889)
Total length = 12 × 10: 120.00 m
Total weight = w × length: 106.5 kg

Metric rebar (IS 1786 nominal mass)

Diameter

kg/m

Per 12 m bar

6 mm

0.222

2.66 kg

8 mm

0.395

4.74 kg

10 mm

0.617

7.40 kg

12 mm

0.888

10.65 kg

16 mm

1.578

18.94 kg

20 mm

2.466

29.59 kg

25 mm

3.853

46.24 kg

32 mm

6.313

75.76 kg

40 mm

9.865

118.38 kg

US rebar (ASTM A615)

Size

lb/ft

Per 20 ft bar

0.376

7.5 lb

0.668

13.4 lb

1.043

20.9 lb

1.502

30.0 lb

2.044

40.9 lb

2.670

53.4 lb

3.400

68.0 lb

#10

4.303

86.1 lb

#11

5.313

106.3 lb

#14

7.650

153.0 lb

#18

13.600

272.0 lb

Find bar spacing first? →

Rebar Calculator converts spacing to steel area per metre and back.

Need a full bar bending schedule? →

Section Design generates an itemised BBS with shape codes, laps and cutting lengths.

Estimate the whole job →

Roll steel, concrete and formwork into a rate-based Cost Estimator.

Reference only. Weights are nominal at steel density 7850 kg/m³ (ASTM nominal values for US bars); rolling tolerance, ribs, coatings and pipe schedules shift the actual mass slightly. Order quantities should follow a detailed schedule with wastage and lap allowances.

How the Steel Weight Calculator works

Steel is detailed by length but bought and billed by weight. This calculator gives the unit weight of a rebar, a flat plate or a round pipe, then the total weight for a number of pieces of a given length. Switch between metric (mm, m, kg and tonnes) and US units (in, ft, lb).

The unit weight comes from the d²/162 rule, with d in millimetres. It follows from the steel density of 7850 kg/m³: the mass of one metre of a round bar is π/4 × d²/10⁶ × 7850, which works out to d²/162. The total length is the length per bar multiplied by the number of bars, and the total weight is the unit weight multiplied by that length.

In US units, rebar is picked by bar size (#3 to #18) and uses the ASTM A615 nominal weight in lb/ft. Plate weight is width × thickness × 7850 kg/m³, and pipe weight is the ring area π/4 × (D² − (D − 2t)²) × 7850 kg/m³.

If you enter a price per kg (or per lb in US units), in any currency, the calculator also gives the material cost as total weight × price. Reference tables list metric bars from 6 to 40 mm and US bars from #3 to #18.

Unit weight: w = d² / 162 (kg/m, d in mm)
Origin of the rule: w = π/4 × d²/10⁶ × 7850 ≈ d² / 162
Plate: w = b × t × ρ (ρ = 7850 kg/m³)
Pipe: w = π/4 × (D² - (D - 2t)²) × ρ
Total length: L_total = L × n
Total weight: W = w × L_total (kg); W / 1000 (t)
Material cost: Cost = W × price per kg

Worked example: weight and cost of 25 bars of 16 mm, 12 m long

Given

Bar diameter d = 16 mm
Length per bar L = 12 m
Number of bars n = 25
Price = 65 per kg (any currency)

Steps

Unit weight: w = 16² / 162 = 256 / 162 = 1.580 kg/m.
Total length: 12 × 25 = 300 m.
Total weight: 1.5802 × 300 = 474.1 kg, which is 0.474 t.
Material cost: 474.07 × 65 = 30,815.

Result: 474.1 kg (0.474 t) of 16 mm steel, costing about 30,815 at 65 per kg.

Enter the same values in the calculator above to check each step.

Frequently asked questions

What is the weight of 12 mm steel bar per metre?

Using d²/162, a 12 mm bar weighs 144 / 162 = 0.889 kg per metre. A full 12 m length therefore weighs about 10.67 kg.

Why is steel weight calculated as d²/162?

One metre of a round bar has a volume of π/4 × d² mm² × 1 m, and steel weighs 7850 kg/m³. Multiplying these out with d in millimetres gives d² × 0.00617 kg/m, which is the same as d²/162. It is a direct result of the bar area and density, not an empirical fit.

What is the unit weight of 8, 10, 16, 20 and 25 mm bars?

From d²/162: 8 mm is 0.395 kg/m, 10 mm is 0.617 kg/m, 16 mm is 1.580 kg/m, 20 mm is 2.469 kg/m and 25 mm is 3.858 kg/m. For a 12 m bar these are 4.74, 7.41, 18.96, 29.63 and 46.30 kg.

How much does #4 rebar weigh per foot?

A #4 bar (1/2 inch) weighs 0.668 lb per foot by ASTM A615, so a 20 ft bar weighs about 13.4 lb. #3 is 0.376 lb/ft, #5 is 1.043 lb/ft and #6 is 1.502 lb/ft.

How do you calculate the weight of a steel plate?

Multiply width × thickness × length × 7850 kg/m³. A 10 mm plate weighs 78.5 kg per square metre; a 1/4 inch plate weighs about 10.2 lb per square foot.

How do I convert rebar length into tonnes?

Multiply the total length in metres by the unit weight in kg/m and divide by 1000. For example, 300 m of 16 mm bar is 300 × 1.580 = 474.1 kg, or 0.474 t.

Is the d²/162 weight exact enough for ordering steel?

It gives the nominal weight of a round bar at 7850 kg/m³. Rolling tolerance, ribs and coatings make the actual mass differ slightly, and the calculator adds nothing for laps, wastage or bend allowances. Base orders on a detailed bar bending schedule with those allowances included.