Rebar Calculator

Rebar Calculator gives you a fast, clear estimate of the reinforcing-bar quantities for a rectangular concrete slab — how many bars you need each way, the total linear length to order, and the total steel weight. It works completely offline and nothing you enter ever leaves your phone.

HOW IT WORKS
Enter the slab length and width, the bar spacing, the edge cover and the bar size. The app lays out a single orthogonal mat and counts the bars in each direction:

bars across a span = floor((span − 2 × cover) ÷ spacing) + 1

That places a bar at each edge, set in by the cover, with even spacing between. It then multiplies the bar counts by their cut lengths to get the total linear length, and by the bar's mass per metre to get the weight.

Worked example — a 6 m × 4 m slab at 200 mm spacing with 50 mm cover:
• 20 bars run the length (each 5.90 m) and 30 run the width (each 3.90 m)
• 50 bars in total, 235 m of bar
• about 234 kg using #4 (Ø13 mm) bar

WHAT YOU CAN DO
• Enter slab length and width in metres
• Set one bar spacing, or a different spacing each way
• Set the edge cover and pick a bar size from #3 to #8 (Ø10 to Ø25 mm)
• Read the total bar count, linear length and weight instantly
• Open the Details tab for a per-direction breakdown table and a drawn mat preview
• Learn the formula behind the numbers with a plain-language guide

BUILT FOR CLARITY
A clean "Lattice" design in steel blue-grey and safety orange puts the big numbers first, with supporting figures right beside them. Light and dark themes, a tiny download, no clutter and no account required.

AN ESTIMATE, NOT A STRUCTURAL DESIGN
This is a simplified educational tool for a single reinforcing mat. It does not size bars for structural loads and excludes laps, hooks, chairs, bends, wastage and additional layers. Quantities for construction must come from your engineer's drawings and your local building code. This app is for general information and education only and is not engineering advice.

PRIVACY
The app collects no personal data and works fully offline. Ads are served by Google AdMob, which may use an advertising identifier as described in Google's policies.

Download Rebar Calculator and get a quick, sensible take-off of the steel for your next slab.