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Rebar Calculator

Rebar pieces needed for a two-way grid.

Introduction

Rebar Calculator — Rebar pieces needed for a two-way grid. Enter Slab length (m), Slab width (m), Bar spacing (m) to get an instant, accurate result.

Formula

For a two-way rebar grid, bars per direction = floor(span ÷ spacing) + 1, calculated separately for length and width, then summed. This is a standard rebar-spacing estimating method for slab-on-grade reinforcement.

Step-by-step

  1. Enter the Slab length (m).
  2. Enter the Slab width (m).
  3. Enter the Bar spacing (m).
  4. Click Calculate to see your result instantly.

Real-world example

Example: With Slab length (m) = 5, Slab width (m) = 4, Bar spacing (m) = 0.2, the Rebar Calculator gives Length Direction Bars: 26, Width Direction Bars: 21, Total Pieces: 47.

Frequently Asked Questions

Why add 1 to the spacing division?
A grid always has one more bar than the number of gaps between bars — e.g., 4 spaces of rebar require 5 bars.
Does this tell me the total length of rebar needed?
No, it gives the piece count per direction; multiply by span length to get total linear footage, and consider using the Rebar Weight calculator for tonnage.
What inputs does the Rebar Calculator need?
You'll need to provide: Slab length (m), Slab width (m), Bar spacing (m). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Rebar Calculator?
The Rebar Calculator applies the formula exactly as calculated — For a two-way rebar grid, bars per direction = floor(span ÷ spacing) + 1, calculated separately for length and width, then summed. This is a standard rebar-spacing estimating method for slab-on-grade reinforcement. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Rebar Calculator free to use?
Yes, the Rebar Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Rebar Calculator

The Rebar Calculator uses a real, verifiable formula — For a two-way rebar grid, bars per direction = floor(span ÷ spacing) + 1, calculated separately for length and width, then summed. This is a standard rebar-spacing estimating method for slab-on-grade reinforcement. — so results are accurate every time, not an approximation.