Calculate rebar quantity, total length, steel weight, bar count and estimated cost for concrete slabs, beams, foundations and other reinforced concrete projects.
Project Details
Enter the reinforcement area and bar spacing.
How the Rebar Calculator Works
This calculator estimates the amount of reinforcing steel needed for a rectangular concrete area. It uses the area dimensions, bar spacing, bar diameter, standard stock length and an allowance for laps or cutting waste.
For a slab or similar rectangular reinforcement grid, the number of bars is based on the width divided by the selected spacing. The calculator adds one bar so the reinforcement covers the full width.
The same method works as a planning estimate for slabs, walls, footings and other rectangular reinforced concrete sections. Structural reinforcement requirements should always follow the project drawings and specifications prepared by a qualified structural professional.
Rebar Weight Formula
A common formula for the approximate weight of steel reinforcement is:
For example, a 12 mm rebar weighs approximately 0.89 kg per meter. The calculator multiplies the weight per meter by the estimated total bar length to determine the total steel weight.
Common Rebar Weights
| Bar Diameter | Approx. Weight per Meter | Approx. Weight per 12 m Bar |
|---|---|---|
| 6 mm | 0.22 kg/m | 2.67 kg |
| 8 mm | 0.40 kg/m | 4.74 kg |
| 10 mm | 0.62 kg/m | 7.41 kg |
| 12 mm | 0.89 kg/m | 10.67 kg |
| 16 mm | 1.58 kg/m | 18.96 kg |
| 20 mm | 2.47 kg/m | 29.63 kg |
| 25 mm | 3.86 kg/m | 46.30 kg |
| 32 mm | 6.32 kg/m | 75.85 kg |
Rebar Calculator Note
The results are material estimates, not structural design calculations. Bar diameter, spacing, lap length, concrete cover, number of reinforcement layers, bends and anchorage requirements depend on the structural design.
Rebar Calculator FAQs
Enter the reinforcement area dimensions, bar spacing and bar diameter. The calculator estimates the number of bars, total length and total steel weight. A lap and waste allowance can also be added.
12 mm rebar weighs approximately 0.89 kg per meter. A 12 meter bar weighs about 10.67 kg using the standard diameter-based steel weight formula.
The number depends on the reinforcement layout. Enter the area length, width and spacing in the calculator. It estimates the total reinforcement length and divides it by the selected stock bar length.
A commonly used metric formula is diameter squared divided by 162. The diameter is entered in millimeters, and the result gives the approximate steel weight in kilograms per meter.
The allowance adds extra material for cutting, joining bars and normal installation waste. It does not replace the lap lengths specified by structural drawings.
No. It provides a quantity and weight estimate. Structural reinforcement needs depend on loads, spans, concrete strength, steel grade, cover, detailing rules and the structural design.