Round, Square & Flat Bar Weight and Cost Calculator
Calculate weight per piece and total weight for round, square and flat bar from dimensions, material density and quantity.
How is bar weight calculated? - Calculation Methodology
Our calculator uses precise mathematical and physical formulas to calculate
the weight of bars of different shapes. Depending on the selected bar type,
different formulas are used:
Round Bars
The weight of a round bar is calculated based on the formula:
Weight = π × (Diameter/2)² × Length × Density
where:
π (pi) - mathematical constant approx. 3.14159
Diameter - diameter of the bar [m]
Length - length of the bar [m]
Density - material density [kg/m³]
Dimensions provided in millimeters are automatically converted to meters
during calculations.
Square Bars
The weight of a square bar is calculated based on the formula:
Weight = Side² × Length × Density
where:
Side - side length of the square cross-section [m]
Length - length of the bar [m]
Density - material density [kg/m³]
Flat Bars
The weight of a flat bar is calculated based on the formula:
Weight = Width × Thickness × Length × Density
where:
Width - width of the bar cross-section [m]
Thickness - thickness of the bar cross-section [m]
Length - length of the bar [m]
Density - material density [kg/m³]
Calculation Examples
Example 1: Round Steel Bar
Data:
Diameter: 20 mm (0.02 m)
Length: 1000 mm (1 m)
Material: plain steel (7850 kg/m³)
Calculation:
Weight = π × (0.02/2)² × 1 × 7850
Weight = 3.14159 × 0.0001 × 1 × 7850
Weight = 2.466 kg
Example 2: Square Aluminium Bar
Data:
Side: 15 mm (0.015 m)
Length: 2000 mm (2 m)
Material: aluminium (2700 kg/m³)
Calculation:
Weight = 0.015² × 2 × 2700
Weight = 0.000225 × 2 × 2700
Weight = 1.215 kg
Material Density Table - Reference Data
The table below presents detailed density values for various materials used
for manufacturing rods/bars and utilized in our calculator. Precise density
values are key to obtaining accurate bar weight calculation results:
Material
Density (kg/m³)
Characteristics
Plain Steel (carbon)
7850
Most popular construction material, high strength, good weldability
Stainless Steel
7930
Increased corrosion resistance, used in aggressive environments
Aluminium
2700
Lightweight metal, good corrosion resistance, high
strength-to-weight ratio
Copper
8960
Excellent electrical and thermal conductivity, used in installations
Brass
8500
Copper and zinc alloy, good machinability, corrosion resistance
Lead
11340
Very heavy metal, used as radiation shielding
Titanium
4500
Lightweight, very strong, exceptional resistance to corrosion and
high temperatures
The above density values are standard values for pure materials or typical
alloys used in industry. In practice, depending on the exact alloy
composition, heat treatment, or material quality, the density may vary
slightly (usually by ±1-2%).
Material cost versus fabrication cost
Material cost is total order weight multiplied by your price per kg or per lb. Divide a price per metric tonne by 1000 before using the metric price field. A US short ton is 2000 lb, so check which ton your quotation uses. Divide a quoted sheet price by its weight to compare suppliers on the same basis. This tool does not fetch current steel prices or exchange rates. Cutting, bending, welding, finishing, delivery and tax are separate items. If you must buy whole stock lengths or sheets, include the unused material in the purchasing budget.
Round bar, square bar and flat bar weight per metre
For a solid steel round bar, kg/m = π × d² / 4 × 0.00785 with diameter d in mm. A 10 mm bar weighs about 0.617 kg/m, a 12 mm bar 0.888 kg/m and a 20 mm bar 2.466 kg/m. Multiply by the purchased length and number of bars.
Square bar area is side²; flat bar area is width × thickness. A 40 × 5 mm flat bar weighs approximately 1.57 kg/m. Doubling round-bar diameter quadruples its area and mass. Reinforcing bar uses nominal product dimensions and may have ribbed surfaces: verify its published nominal mass rather than measuring across the ribs.
Theoretical weight reference
Fixed examples for carbon steel at an assumed density of 7850 kg/m³, not every steel grade. The table does not change with the calculator’s material selection. For stainless steel or other metals, use the appropriate density in the calculator. Cross-section dimensions are in mm; coatings, corner radii and tolerances are excluded. These are geometric estimates, not manufacturer catalogue weights.
Carbon steel · ρ = 7850 kg/m³ · d = 20 mm
Length
Weight
1 m
2.466 kg
2 m
4.932 kg
3 m
7.398 kg
6 m
14.797 kg
Check this worked example
A = π × d² / 4
314.159 mm² × 0.00785 = 2.466 kg/m
Practical Application Examples of Bar Weight Calculations
Discover practical examples of using bar weight calculations in various
industrial and construction applications:
Example 1: Reinforcement of a concrete structure
Scenario: A construction company needs to calculate the
weight of reinforcing bars for a foundation slab measuring 12×15 m.
Required data:
Ribbed round bars with a diameter of 12 mm
Bar spacing: 15 cm in both directions
Bar lengths: 12 m and 15 m
Material: reinforcing steel (7850 kg/m³)
Calculations:
Number of 12 m bars: 15 m / 0.15 m = 100 pieces
Number of 15 m bars: 12 m / 0.15 m = 80 pieces
Weight of one 12 m bar: π × (0.012/2)² × 12 × 7850 = 10.62 kg
Weight of one 15 m bar: π × (0.012/2)² × 15 × 7850 = 13.27 kg
Total weight: (100 × 10.62) + (80 × 13.27) = 1062 + 1061.6 = 2123.6 kg
Application: Thanks to these calculations, the company
can accurately plan material purchases, transport reinforcement to the
construction site, and determine the costs for this part of the
investment.
Example 2: Balustrade production
Scenario: A metal workshop received an order for 20
balcony railings, each 3 m long.
Required data:
Frame made of 20×20 mm square bar
Infill with 12 mm diameter round bars (15 pieces per railing)
Railing height: 1.1 m
Material: plain steel (7850 kg/m³)
Calculations:
Length of square bar per railing: 2 × 3 m + 2 × 1.1 m = 8.2 m
Weight of square bar: 0.02² × 8.2 × 7850 = 25.76 kg
Length of round bar per railing: 15 × 1.1 m = 16.5 m
Weight of round bar: π × (0.012/2)² × 16.5 × 7850 = 14.6 kg
Weight of one railing: 25.76 + 14.6 = 40.36 kg
Total weight: 20 × 40.36 = 807.2 kg
Application: Calculations allow determining material
cost, planning the production process, and transporting the finished
railings to the client.
Applications of Bars - Industries and Use Cases
Metal bars are extremely versatile construction materials used in many
industrial and construction sectors. Below are the most important
applications for different types of bars:
Round Bars
Round bars find wide application in the following fields:
Construction - reinforcements, anchors, threaded rods
Mechanical Engineering - shafts, axles, rotating
elements
Metalwork - handrails, railings, decorative elements
Furniture production - frames, structural elements
Automotive industry - elements of power transmission
systems
Square Bars
Square bars are commonly used in:
Steel structures - frames, supports, mountings
Artistic metalwork - decorative elements, grates
Furniture industry - table legs, frames,
reinforcements
Fences and railings - spans, posts
Industrial halls - structural and support elements
Frequently Asked Questions (FAQ) - Comprehensive Information
We have gathered answers to the most frequently asked questions about
calculating bar weight and using our calculator. If you don't find the
answer to your question here, please contact us directly.
The most common standard bar lengths available on the market are:
3000 mm (3 meters)
6000 mm (6 meters)
12000 mm (12 meters)
Shorter lengths are usually available as cut pieces. For large
orders, many warehouses also offer cutting bars to size according to
customer needs, which can help optimize transport costs and reduce
waste.
To convert dimensions from inches to millimeters, multiply the value
in inches by 25.4. For example:
1/4 inch diameter bar = 6.35 mm
1/2 inch diameter bar = 12.7 mm
1 inch diameter bar = 25.4 mm
2 inch diameter bar = 50.8 mm
In industrial practice, especially in an international context, it
is always worth confirming whether dimensions are in the metric or
imperial system to avoid errors in calculations and orders.
The main difference between a bar and a tube lies in their
construction:
Bar - is a solid element, full throughout its
cross-section (e.g., a round bar is simply a cylinder)
Tube - is a hollow element, having a hole along
its entire length
This fundamental difference significantly impacts the properties of
these elements:
Tubes are lighter than bars of the same outer diameter
Tubes have a better stiffness-to-weight ratio for bending loads
Bars have greater strength against torsion and axial compression
Tubes can additionally serve as conduits for transporting media
Note: Round Bars
vs. Tubes
Do not confuse solid round bars with tubes, which are hollow
elements.
To calculate the weight of tubes, use the
pipe and profile calculator, which takes into account both the outer and inner diameter.
To calculate the weight of a bar with a non-standard cross-section,
you need to:
Calculate the cross-sectional area in m²
Multiply the cross-sectional area by the length of the bar in m
Multiply the resulting volume by the material density in kg/m³
For example, for a bar with a trapezoidal cross-section:
Cross-sectional area = ((long base + short base) × height) / 2
Volume = cross-sectional area × length
Weight = volume × material density
For very complex shapes, it may be necessary to use advanced
calculation methods or CAD software to accurately determine the
volume.
Dimensional tolerances for bars depend on their production method,
material, and applicable standards in a given country. Typical
dimensional tolerances are:
Cold-drawn bars: typically ±0.05 mm to ±0.2 mm,
depending on the diameter
Hot-rolled bars: usually ±0.3 mm to ±1.0 mm
Ground bars: tolerances can be much smaller, even
down to ±0.01 mm
Exact tolerance values are specified by technical standards, such
as:
BS EN 10060 - for hot-rolled round bars
BS EN 10059 - for hot-rolled square bars
BS EN 10058 - for hot-rolled flat bars
BS EN 10278 - for drawn or ground steel bars
For precise weight calculations for large quantities of bars, it is
worth considering these tolerances, especially for bars with large
diameters, where even small dimensional deviations can affect the
final weight.
