Footing Rebar Calculator — Continuous Footing Steel
Estimate longitudinal rebar and stirrups for a continuous strip footing. Returns bar piece count, total lineal feet, and total weight for #3 through #8 bars.
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 continuous strip footing carries the load of a foundation wall down to bearing soil. Longitudinal rebar resists bending across soft spots and distributes wall loads evenly. Stirrups (where required) tie the longitudinal bars into a cage and resist diagonal tension forces.
This calculator estimates longitudinal rebar and optional stirrups for a continuous strip footing. For spread footings, raft slabs, or engineered foundations, use project-specific structural drawings instead.
How to Estimate Footing Rebar
Longitudinal LF = Bar Count × Footing Length × (1 + lap %). Stirrups: Stirrup Perimeter × ⌈Footing Length ÷ Stirrup Spacing⌉.
Residential Footing Rebar Reference
- 12 inch wide footing: 2 longitudinal #4 bars (1 top, 1 bottom). Stirrups usually not required.
- 16-18 inch wide footing: 2 bottom + 2 top #4 or #5 bars. Stirrups optional, per engineered drawings.
- 24+ inch wide footing: 3-4 bottom + 2 top #5 bars with #3 stirrups at 12 inch OC.
- Concrete cover: 3 inches from earth-cast sides and bottom; 2 inches from formed sides; 1.5 inches from top.
Frequently Asked Questions
How many rebar bars in a strip footing?
Typical residential continuous strip footings use 2 longitudinal #4 or #5 bars top and bottom, plus #3 stirrups at 12-16 inch on-center. Wider footings (24 inch+) often run 3-4 longitudinal bars.
What size rebar for a footing?
#4 (1/2 inch) is the residential minimum for continuous strip footings. #5 (5/8 inch) is more common for 24 inch+ wide footings or where the footing supports a load-bearing CMU wall. Verify per engineered drawings.
How deep should rebar sit in a footing?
ACI 318 requires 3 inches of concrete cover when cast against earth. So in a 12 inch deep footing, rebar sits 3 inches up from the bottom on chairs or bricks. Top bars (where required) sit 1.5–2 inches down from the top.
Do residential footings always need rebar?
Not always — IRC R403 allows plain (unreinforced) footings for one- and two-family dwellings with light loads on stable soil. But most jurisdictions and engineers specify reinforced footings for any wall over one story or in expansive soils. Confirm locally.
How long should I lap-splice footing rebar?
ACI 318 specifies 40× bar diameter for typical Class B tension lap splices. For #4 bar: 40 × 0.5 = 20 inches. For #5 bar: 40 × 0.625 = 25 inches. Stagger laps along the run.
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 →