The steel weight calculation guide covers an engineering process of critical importance across many fields, from the manufacturing industry to the construction sector. To determine the correct tonnage when placing an order, optimize shipping costs, arrive at accurate results in structural analyses, and efficiently plan your production process, you must accurately calculate the weight of steel materials.
In this guide, we provide a detailed overview of the weight calculation formulas, practical weight tables, and key considerations for calculating the weight of round, square, flat, and hexagonal steel bars included in Uyar Çelik’s product range.
1. The Basic Principle of Steel Weight Calculation
All steel weight calculations are based on a single fundamental physical principle:
Weight (kg) = Volume (cm³) × Density (g/cm³)
The standard density value for steel is accepted as 7.85 g/cm³ (7,850 kg/m³). This value applies to carbon steel and low-alloy steels. The density value may vary for high-alloy or special steels.
Therefore, the calculation of weight is based on three pieces of information:
The material’s geometric shape (round, square, flat bar, hexagonal)
Dimensions (diameter, side length, thickness, length)
Material density (g/cm³ or kg/m³)
Density Values of Different Types of Steel
| Steel Type | Density (g/cm³) | Density (kg/m³) |
|---|---|---|
| Carbon Steel (S235, S355) | 7.85 | 7850 |
| Quenched and Tempered Steel (42CrMo4, C45) | 7.85 | 7850 |
| Free-Cutting Steel (11SMn30) | 7.85 | 7850 |
| Stainless Steel (304) | 7.93 | 7930 |
| Stainless Steel (316) | 7.98 | 7980 |
| Tool Steel (1.2379 / D2) | 7.70 | 7700 |
2. Round Steel Bar Weight Calculation
Round steel bars are the most commonly used profile shape in industry. Hot-drawn round steel (EN 10060) has a wide range of applications, from shaft manufacturing to machine parts. At Uyar Çelik, we produce hot-drawn round steel in compliance with the EN 10060 standard.
Formula
Weight (kg/m) = d² × 0.006165
Here, d represents the diameter (mm).
The formula is derived as follows:
Weight (kg/m) = (π / 4) × d² × ρ / 1,000,000
Here, ρ = 7.85 g/cm³ and d is in mm. The constant factor 0.006165 is derived from (π/4) × 7.85 / 1000.
Example Calculation
The weight of a round steel bar with a diameter of 50 mm and a length of 6 meters:
Weight per meter = 50² × 0.006165 = 2,500 × 0.006165 = 15.41 kg/m
Total weight = 15.41 × 6 = 92.46 kg
Round Steel Bar Weight Chart (Weights per Meter)
| Diameter (mm) | kg/m | Diameter (mm) | kg/m |
|---|---|---|---|
| 10 | 0.617 | 60 | 22.19 |
| 12 | 0.888 | 65 | 26.05 |
| 14 | 1.208 | 70 | 30.21 |
| 16 | 1.578 | 75 | 34.68 |
| 18 | 1.998 | 80 | 39.46 |
| 20 | 2.466 | 85 | 44.55 |
| 22 | 2.984 | 90 | 49.94 |
| 25 | 3.853 | 95 | 55.64 |
| 28 | 4.834 | 100 | 61.65 |
| 30 | 5.549 | 110 | 74.60 |
| 32 | 6.313 | 120 | 88.78 |
| 35 | 7.553 | 130 | 104.18 |
| 38 | 8.903 | 140 | 120.82 |
| 40 | 9.864 | 150 | 138.67 |
| 42 | 10.878 | 160 | 157.76 |
| 45 | 12.484 | 170 | 178.07 |
| 48 | 14.205 | 180 | 199.61 |
| 50 | 15.413 | 200 | 246.30 |
3. Square Steel Bar Weight Calculation
Square steel bars (EN 10059) are commonly used in machine manufacturing, steel construction, and the production of agricultural equipment. Uyar Çelik manufactures hot-drawn square steel bars in accordance with the EN 10059 standard.
Formula
Weight (kg/m) = a² × 0.00785
Here, a represents the side length (mm). The constant factor 0.00785 is equal to 7.85 / 1000.
Sample Calculation
40 × 40 mm square steel, 6 meters in length:
Weight per meter = 40² × 0.00785 = 1,600 × 0.00785 = 12.56 kg/m
Total weight = 12.56 × 6 = 75.36 kg
Square Steel Bar Weight Chart
| Side (mm) | kg/m | Side (mm) | kg/m |
|---|---|---|---|
| 10 | 0.785 | 55 | 23.74 |
| 12 | 1.130 | 60 | 28.26 |
| 14 | 1.539 | 65 | 33.16 |
| 16 | 2.010 | 70 | 38.47 |
| 18 | 2.543 | 75 | 44.16 |
| 20 | 3.140 | 80 | 50.24 |
| 22 | 3.798 | 85 | 56.70 |
| 25 | 4.906 | 90 | 63.59 |
| 28 | 6.154 | 95 | 70.86 |
| 30 | 7.065 | 100 | 78.50 |
| 32 | 8.038 | 110 | 94.94 |
| 35 | 9.616 | 120 | 113.04 |
| 40 | 12.560 | 130 | 132.67 |
| 45 | 15.896 | 140 | 153.86 |
| 50 | 19.625 | 150 | 176.63 |
4. Steel Bar (Flat Bar) Weight Calculation
Steel flat bars are flat steel bars with a rectangular cross-section (EN 10058). They are widely used in mold making, steel construction, machine manufacturing, agricultural tools and equipment, and the general metalworking industry. Uyar Çelik manufactures hot-rolled steel flat bars in accordance with the EN 10058 standard.
Formula
Weight (kg/m) = a × b × 0.00785
Here, a represents the width (mm) and b represents the thickness (mm).
Example Calculation
60 × 10 mm bar, 6 meters in length:
Weight per meter = 60 × 10 × 0.00785 = 4.71 kg/m
Total weight = 4.71 × 6 = 28.26 kg
5. Hexagonal Steel Bar Weight Calculation
Hexagonal steel bars (EN 10061) are particularly preferred for the production of bolts, nuts, hydraulic fittings, and automatic lathe work. Uyar Çelik manufactures hot-drawn hexagonal steel bars in accordance with the EN 10061 standard.
Formula
Weight (kg/m) = s² × 0.006798
Here, s represents the distance between opposing faces / keyway dimension (mm).
Derivation of the constant factor: 0.006798 = (3√3 / 2) × 7.85 / 1,000,000 × 10⁶. The formula for the hexagonal cross-sectional area is derived from (3√3/2) × s².
Sample Calculation
SW 32 mm hexagonal steel, 6 meters in length:
Weight per meter = 32² × 0.006798 = 1,024 × 0.006798 = 6.96 kg/m
Total weight = 6.96 × 6 = 41.76 kg
Hexagonal Steel Bar Weight Chart
| SW (mm) | kg/m | SW (mm) | kg/m |
|---|---|---|---|
| 10 | 0,680 | 41 | 11,43 |
| 12 | 0,979 | 46 | 14,39 |
| 14 | 1,332 | 50 | 16,99 |
| 17 | 1,964 | 55 | 20,56 |
| 19 | 2,453 | 60 | 24,47 |
| 22 | 3,290 | 65 | 28,72 |
| 24 | 3,914 | 70 | 33,30 |
| 27 | 4,955 | 75 | 38,23 |
| 30 | 6,118 | 80 | 43,51 |
| 32 | 6,957 | 85 | 49,11 |
| 34 | 7,857 | 90 | 55,07 |
| 36 | 8,809 | 95 | 61,36 |
| 38 | 9,812 | 100 | 67,98 |
6. Summary Table of All Formulas
| Profile Shape | Formula (kg/m) | Constant Factor | Standard |
|---|---|---|---|
| Round | d² × 0.006165 | 0.006165 | EN 10060 |
| Square | a² × 0.00785 | 0.00785 | EN 10059 |
| Flat | a × b × 0.00785 | 0.00785 | EN 10058 |
| Hexagonal | s² × 0.006798 | 0.006798 | EN 10061 |
7. Key Considerations in Weight Calculation
Differences in Tolerance
The weight values given in the tables and formulas are theoretical (nominal) values. Actual weights may deviate from these values depending on manufacturing tolerances. According to EN standards, dimensional tolerances for steel bars generally range from ±1% to ±5%. These tolerances directly affect the weight.
The Impact of Steel Quality
A density of 7.85 g/cm³ can be used for standard structural steels (S235, S355) and high-strength steels (C45, 42CrMo4). However, since the density differs for high-alloy steels (stainless steel, tool steels), you must recalculate the constant factor in the formula using the material-specific density value.
Unit Conversions
The measurements in our formulas are in millimeters (mm). If you are working with different units, you can use the following conversion factors:
1 inch = 25.4 mm
1 cm = 10 mm
1 kg = 2.2046 lb
1 ton = 1,000 kg
The Difference Between Hot-Rolled and Cold-Drawn
The densities of hot-rolled and cold-drawn steels are practically the same; therefore, the same formulas are used. However, since dimensional tolerances are tighter in cold-drawn products, the difference between the theoretical and actual weights will be smaller.
Applications in Transportation and Logistics Planning
Accurate weight calculations for steel orders directly impact shipping costs. By taking into account the load capacity of trucks (typically 24–27 tons), adjusting the order quantity to align with the optimal shipment tonnage provides a cost advantage. At Uyar Çelik, we offer our customers the most efficient logistics planning from our facilities in Istanbul, Kocaeli, and Karabük.
8. The Importance of Accurate Weight Calculation in Industry
Accurate steel weight calculations directly impact many industrial processes:
Cost Estimation: Steel materials are typically priced per kilogram or ton. Calculating the weight accurately prevents errors in budget planning.
Structural Analysis: In engineering projects, the steel weight must be known to calculate the dead load of structural members.
Transportation Optimization: Without tonnage information, you cannot properly plan vehicle capacity. Incorrect calculations lead to underloading or overloading.
Production Planning: The weight of bars to be processed on CNC machines is necessary for calculating scrap rates and determining raw material requirements.
Crane and Lifting Capacity: Weight information is essential to ensure that the capacity of storage and handling equipment is not exceeded.
Frequently Asked Questions (FAQ)
Where does the number 0.00785 come from in steel weight calculations?
This constant is obtained by dividing the density of steel, 7.85 g/cm³, by 1000 (7.85 / 1000 = 0.00785). This conversion is necessary to convert measurements entered in millimeters to the kg/m unit.
Can I use the same formula for stainless steel?
No. The density of stainless steel varies (7.93 g/cm³ for grade 304 and 7.98 g/cm³ for grade 316). You need to recalculate the constant factor in the formula using the appropriate density value. For example, the square cross-section factor for 304 stainless steel would be 0.00793.
How much of a difference is there between the theoretical weight and the actual weight?
In production compliant with EN standards, the difference between theoretical and actual weight typically ranges from 1% to 5%. While this difference remains around 1–2% for cold-drawn products, the tolerance range is slightly wider for hot-rolled products.
When ordering steel bars, is weight or length more important?
Both are important. Orders are typically placed based on quantity and size, but pricing is calculated per kilogram or ton. Therefore, knowing both the quantity/size and the tonnage of your order is critical for budgeting and logistics.
Result: Steel Weight Calculation Guide: Formulas for Round, Square, Flat, and Hexagonal Shapes
Calculating the weight of steel is an extremely simple process once you know the correct formula. The weight formulas and tables for round, square, flat, and hexagonal steel bars shared in this guide provide values that you can use as a practical reference in your daily work.
As Uyar Çelik, with half a century of experience, we produce hot-rolled and cold-drawn steel in compliance with EN 10058, EN 10059, EN 10060, and EN 10061 standards. You can contact us for detailed information about our products manufactured at our facilities in Istanbul, Kocaeli, and Karabük, as well as for custom size requests.
Do you need steel bars in custom sizes?
Contact Uyar Çelik’s team of experts. You can receive technical support and a price quote for our range of hot-rolled and cold-drawn steel bars.
Phone: +90 (212) 485 9898 | Website: uyarcelik.com
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