Column Rebar Calculator — Vertical Bars & Ties
Estimate vertical rebar and ties for a reinforced concrete column. Returns bar piece count and total linear feet for any column height per ACI 318.
Enter Dimensions
Add 10% for standard cuts and overlaps
Results
Bars Needed
38bars
Total Lineal Feet
608lin ft
Total rebar length including waste
Total Weight
406lb
#4 rebar weight per CRSI
Slab Area
240sq ft
Editorial Standards
Each calculator is reviewed for formula accuracy, unit consistency, and alignment with current U.S. building practices before publication. We verify outputs against published engineering references and real-world project data. Learn more about our methodology.
A reinforced concrete column transfers vertical load from a beam, slab, or roof down to a footing. The vertical bars carry compression and bending; ties prevent the verticals from buckling outward. Both must be sized and spaced per ACI 318 for the column to perform as designed.
This calculator counts vertical bars and ties for a tied rectangular column. For spiral columns or engineered designs, use the project structural drawings as the authoritative source.
How to Estimate Column Rebar
Vertical LF = bars × (column height + lap + dowel). Tie LF = tie perimeter × ⌈column height ÷ tie spacing⌉.
ACI 318 Column Reference
- Minimum vertical bars: 4 in rectangular tied columns; 6 in spiral columns.
- Minimum vertical steel ratio: 1% of gross section area (also a 8% maximum).
- Maximum tie spacing: least of 16 × vert bar dia, 48 × tie bar dia, or smallest column dimension.
- Concrete cover: 1.5 in interior, 2 in earth-formed, 3 in cast against earth.
Frequently Asked Questions
How many vertical bars in a concrete column?
ACI 318 requires a minimum of 4 vertical bars in a rectangular tied column. Residential columns typically use 4 to 8 bars depending on column size and load. Round columns use a minimum of 6 bars in a spiral configuration.
What size rebar for a residential porch column?
#4 or #5 vertical bars with #3 ties for typical 8-12 inch residential columns. Heavier loads, larger columns, or seismic conditions warrant #5 to #8 verticals with engineering review.
How are column ties spaced?
ACI 318 sets maximum tie spacing as the smaller of: 16 × vertical bar diameter, 48 × tie bar diameter, or the least column dimension. Typical practice: 12 inches OC for #3 ties on residential columns.
Do I need a tied cage or a spiral cage?
Tied cages (rectangular ties at intervals) are standard for rectangular and square columns. Spiral cages (continuous helical tie) are used for round columns and provide better confinement in seismic conditions.
How much rebar in an 8 inch × 8 inch × 10 ft column?
4 vertical #4 bars × 10 ft = 40 ft. Plus 10 ties at 12 inch OC, each ~2.5 ft long = 25 ft of #3. Total ≈ 26.7 lb of #4 + 9.4 lb of #3 = 36 lb of rebar for the column.
Looking for the general calculator?
Calculate rebar quantity, spacing, and total weight for concrete slabs, footings, and walls. Covers #3 through #8 bar sizes using CRSI published weight tables.
Open the Rebar Calculator: Bar Count & Weight →