What Is a Concrete Footing Rebar Quantity Calculator?
Most footings use a two-way mat of reinforcing bar: one set of bars running along the length of the footing, and a perpendicular set running along the width, both spaced on-center. This calculator counts how many bars are needed in each direction based on your spacing, then adds up the total linear footage — including extra length for lap splices where a bar run is longer than your supplier's stock bar length.
Getting the bar count and lap allowance right avoids two common takeoff mistakes: ordering too few bars for the spacing you specified, and forgetting that any run longer than a standard 20 ft or 40 ft stick needs an overlapping splice, not just a butt joint.
How to Read Your Results
Total Linear Feet of Rebar
The full length of bar needed for both directions combined, including lap splice length — the number to use when ordering rebar by the foot or converting to stock lengths.
Bars Running Lengthwise / Widthwise
The bar count in each direction of the mat, based on the on-center spacing you entered. The first bar sits at the edge, with additional bars added every spacing interval.
Lap Splice Allowance
The extra length added because one or more bar runs are longer than your stock bar length and need an overlapping splice rather than a single continuous bar.
Stock Bars Needed
An estimate of how many full-length stock bars to order, based on total linear footage divided by your stock bar length, rounded up.
Real-World Example
A continuous strip footing runs 40 ft long by 2 ft wide, reinforced at 12-inch spacing, using 20 ft stock bars and a 24-inch lap splice.
| Item | Value |
|---|---|
| Bars running lengthwise (across the 2 ft width) | 3 bars |
| Bars running widthwise (across the 40 ft length) | 41 bars |
| Lap splice allowance | 6 ft |
| Total linear feet | ≈202 ft |
Because the 40 ft length exceeds the 20 ft stock bar length, each of the 3 lengthwise bars needs one lap splice, adding 6 ft of extra bar to the total order.
Tips for Footing Rebar Takeoffs
- Confirm spacing and cover requirements with your local building code or engineer's drawings before ordering.
- Always round bar counts up, never down — this calculator already does that automatically.
- Lap splice length varies by bar size, concrete strength and splice class — check your project specification rather than relying on a single default value.
- Add chairs or dobies to the order separately to hold rebar at the correct height and cover during the pour.
Related Calculators
Last updated: August 2026 · Reviewed by: Simple Calculator Tools Editorial Team