How to use it
- Enter bar diameter in inches.
- Enter spacing between bars in inches.
- Click Calculate to see weight per square foot.
- Copy the result for your material list.
What it does – The calculator converts the diameter of a steel rebar and its on‑site spacing into the weight that will sit on each square foot of slab or wall. Knowing pounds per square foot lets engineers size concrete mixes, estimate labor, and stay within code‑mandated load limits. The tool uses the industry‑standard weight‑per‑foot formula (0.668 × d²) and divides by the spacing you provide, so the output is ready to plug into structural calculations or bid sheets. No extra steps, just input and read the number. The result is expressed in lb/ft², the unit most specifications request. Because the calculation is done instantly, you can compare multiple bar sizes or spacing plans without leaving the page. It’s especially handy during preliminary design when you’re balancing strength, cost, and material availability. The calculator also shows the raw weight per foot, so you can verify the intermediate step if you wish.
Pro tips
- Add 10% waste when ordering rebar to cover cuts and overlaps.
- Round the result to two decimal places for bids; most specs accept ±0.05 lb/ft².
- Use the raw weight‑per‑foot value to check supplier tables for consistency.
- Double‑check spacing units; entering centimeters will give incorrect pounds per square foot.
Real-life examples
- A residential contractor estimating rebar for a 2,000 ft² slab.
- A structural engineer sizing reinforcement for a commercial parking garage.
- A DIY homeowner planning a concrete patio and needing accurate material weight.
Case study
John, a small‑business contractor, entered a 0.75 in bar at 16 in spacing and saw the weight drop from 0.38 lb/ft² to 0.19 lb/ft² after switching to 12 in spacing, letting him cut material costs by 12%.