Use our powerful online tools to calculate stairs, concrete, roofing, material costs, and more — all in one place.
Ready to estimate rebar like a pro? Our Rebar Calculator gives you everything you need to size, weigh, and price your steel reinforcement—whether you’re pouring a concrete slab, laying a foundation, or building a wall.
🧮 Combine it with our Concrete Block Calculator for a full building estimate.
Advanced Rebar Calculator
Supporting US, UK, and EU construction standards
Units:
ft
in
Enter spacing to calculate the number of bars needed for a given area
ft²
Enter area to calculate the total bars needed with the specified spacing
Straight Bar
L-Shape
U-Shape
Stirrup
Spiral
ft
Unit Conversion
ft
m
Conversion Formula: 1 ft = 0.3048 m
Rebar Size Equivalents
Equivalent Size: -
Diameter: -
Cross-Section Area: -
US Standard Rebar Reference (#)
| Bar Size | Diameter (in) | Area (in²) | Weight (lb/ft) |
|---|
UK/EU Standard Rebar Reference (mm)
| Bar Size (mm) | Diameter (mm) | Area (mm²) | Weight (kg/m) |
|---|
Important Information
Standard Specifications:
- US: ASTM A615, A706
- UK: BS 4449
- EU: EN 10080
Common Applications:
- Slabs and Pavements: #3, #4, #5 (10mm, 12mm, 16mm)
- Beams and Columns: #5, #6, #7, #8 (16mm, 20mm, 22mm, 25mm)
- Heavy Foundations: #9, #10, #11, #14 (28mm, 32mm, 36mm, 43mm)
Conversion Factors:
- 1 inch = 25.4 mm
- 1 foot = 0.3048 meters
- 1 lb/ft = 1.4882 kg/m
- 1 in² = 645.16 mm²
Rebar Placement Guidelines:
- Minimum concrete cover: 1.5" (38mm) for exterior exposure
- Typical spacing: 6" to 18" (150mm to 450mm) depending on application
- Typical lap splice length: 40 x bar diameter
Disclaimer: This calculator is provided for estimation purposes only. Always consult with a licensed structural engineer for final design decisions and comply with local building codes.
Rebar Calculator – Complete Reinforcement Estimator for Concrete Projects
What Is a Rebar Calculator?
A rebar calculator is a digital tool used to calculate the quantity, length, weight, and spacing of rebars (reinforcement bars) required in concrete structures such as slabs, footings, walls, and columns. Whether you’re a contractor, civil engineer, architect, or DIY builder, using a steel rebar calculator helps you accurately estimate material needs and control construction costs.
With construction standards differing globally, our advanced Rebar Calculator supports:
US Standard (Imperial units and bar sizes like #3, #4, #5)
UK Standard (metric units: Ø8 mm, Ø10 mm, Ø12 mm)
EU/EN Standard (reinforcement bars measured in mm)
Why Accurate Rebar Calculations Matter
Incorrect reinforcement calculations can lead to:
Structural weakness or failure
Cost overruns from excess material
Delays due to shortages on-site
With this tool, you can:
Calculate rebar for slab
Estimate rebar for footings
Plan reinforcement for concrete walls
Convert units (ft to m, lb to kg, etc.)
Calculate rebar weight and tonnage
Key Features of the Advanced Rebar Calculator
Multiple Rebar Shapes
Select from standard and custom bar shapes:
Straight Rebar
L-Shaped
U-Shaped
Stirrups
Spirals
Supports Area-Based Calculations
Enter total area (in ft² or m²) and spacing to determine:
Number of bars
Length per bar
Total reinforcement weight
Real-Time Unit Conversion
Quickly switch between:
Imperial & Metric
Feet to Meters
Inches to Millimeters
Pounds to Kilograms
Regional Bar Standards
Get bar size equivalents across:
US Rebar Sizes (#3, #4, #5…)
UK Standards (Ø8 mm to Ø20 mm)
EU DIN/EN formats
How to Use the Rebar Calculator
Select Region: Choose between US, UK, or EU standards.
Choose Units: Imperial (ft, in, lb) or Metric (m, mm, kg).
Enter Shape and Size: Select rebar type and size (e.g., #4 bar).
Input Dimensions: Add length per bar, number of bars, or area and spacing.
Optional Cost Estimation: Add price per rebar unit to calculate total material costs.
Click Calculate: Instantly view quantity, weight, length, and cost results.
Example: Rebar Slab Calculator in Action
Let’s say you’re reinforcing a 20×20 ft concrete slab using #4 bars spaced every 12 inches.
Slab Area: 400 ft²
Bar Spacing: 12 in
Total Length: ~800 ft
Unit Weight of #4 bar: 0.668 lb/ft
Total Weight: ~534.4 lb (0.2672 tons)
Need to calculate the rebar tonnage? Our built-in rebar ton calculator converts it directly.
Common Use Cases
Slab Rebar Calculator – for floors and flatwork
Footing Rebar Calculator – for perimeter and strip footings
Wall Rebar Calculator – vertical and horizontal reinforcement
Rebar Grid Calculator – for mesh-style layouts
Concrete and Rebar Calculator – combine with concrete volume
Rebar Weight Calculation Formula
Formula to calculate rebar weight:
For example, if you’re using 50 bars of 20 ft each (#4), the total weight would be:
Use our rebar weight calculator to automate this!
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Helpful Rebar Resources
Rebar Size Chart
Rebar Overlap & Development Lengths
Concrete Cover Requirements (US, UK, EU)
Bar Bending Schedule (BBS) Guide
PDF Export Options for On-site Use
Build Stronger with Accurate Reinforcement
Whether you’re working on a driveway, foundation, or structural wall, our Rebar Calculator takes the guesswork out of reinforcement planning. By pairing it with tools like our Concrete Block Calculator, you ensure every component of your construction project is planned with precision and cost-efficiency.