Calculate the total weight of steel reinforcement bars for any project. Enter bar diameter and length for multiple entries — get instant weight in kg and tonnes for accurate material ordering.
Multiple Bar EntriesKg & Tonnes
Bar Entries
Results
Dia (mm)
Length (m)
Qty
kg/m
Subtotal (kg)
Total Weight—
Total Weight (Tonnes)—
Estimated Cost—
Total: — kg
Unit weight (kg/m) = D² ÷ 162 where D is diameter in mm (derived from steel density 7850 kg/m³)
Reverse Calculation — Length from Weight
Results
Bar Diameter—
Unit Weight (kg/m)—
Number of Bars—
Length per Bar—
Total Length: — m
Formula: Length per bar = Target weight ÷ (kg/m × quantity)
Steel Rebar Weight Formula
The universally used formula for calculating the weight of a steel reinforcement bar is:
Weight (kg/m) = D² ÷ 162
Where D is the diameter of the bar in millimetres. This formula is derived from first principles using the density of steel (7850 kg/m³) and the cross-sectional area of the bar (π/4 × D²). The constant 162 is an approximation of (4 × 1000²) ÷ (π × 7850) ≈ 162.2, making field calculations fast and accurate to within 0.1%.
To get the total weight for a batch of bars: Total Weight = (D² ÷ 162) × Length (m) × Quantity
Standard Rebar Sizes and Their Uses
Diameter
Unit Weight (kg/m)
Common Use
6 mm
0.222 kg/m
Stirrups, ties, light mesh
8 mm
0.395 kg/m
Stirrups, wall reinforcement, light slabs
10 mm
0.617 kg/m
Residential slabs, footings, ring beams
12 mm
0.888 kg/m
Slabs, beams, columns (general purpose)
16 mm
1.580 kg/m
Beams, columns, retaining walls
20 mm
2.469 kg/m
Heavy columns, bridge structures
25 mm
3.858 kg/m
Structural columns, heavy beams
32 mm
6.313 kg/m
Large columns, heavily loaded structures
40 mm
9.864 kg/m
Piles, large civil engineering works
Frequently Asked Questions
The standard formula is Weight (kg/m) = D² ÷ 162, where D is the bar diameter in millimetres. This is derived from steel's density of 7850 kg/m³ and the circular cross-section area. For total weight: multiply the unit weight by bar length (m) and quantity. Example: 100 bars of 12mm × 6m = (144 ÷ 162) × 6 × 100 = 0.888 × 600 = 532.8 kg.
For residential floor slabs, 10mm or 12mm rebar at 150–200mm centres is most common. Heavily loaded slabs, transfer slabs, or slabs on poor soil may need 16mm or 20mm. Light-duty applications like garden paths often use 8mm or steel mesh. Always check your local building code and consult a structural engineer for load-bearing slabs.
To calculate rebar for a column: (1) Determine the number of vertical main bars (typically 4–8 depending on column size and design — a 300×300mm column often uses 4 × 16mm bars). (2) Calculate bar length = column height + 2 × development/lap length (typically 40× bar diameter above and below). (3) Add lateral ties/stirrups: typically 6mm or 8mm bars at 150–200mm spacing. Use this calculator by adding each bar type as a separate entry to sum the total steel weight.
TMT (Thermo-Mechanically Treated) bars are deformed high-strength steel bars widely used in South Asia. They are produced by quenching hot-rolled bars in water, creating a hard martensitic outer ring and a tough ferrite-pearlite core. Compared to plain mild steel, TMT bars offer higher tensile strength (Fe-415, Fe-500, Fe-550 grades), better ductility, and improved corrosion resistance. The D²/162 weight formula applies to TMT bars of the same diameter since the density of steel remains 7850 kg/m³ regardless of heat treatment.