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Construction Calculators

Rebar Calculator

Verified formula Updated Jun 2026 Private — runs on your device

Enter details
m
m
m
Verified formula Private

Total rebar length

209.00

Number of bars
47

For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.

How to use the Rebar Calculator

The Rebar Calculator works out your total rebar length, along with 1 related figure in an instant. Enter slab length, slab width and bar spacing and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.

  1. Enter the slab length.
  2. Enter the slab width.
  3. Enter the bar spacing.
  4. Read off your total rebar length, together with number of bars — the calculator updates automatically, with no button to press.

Worked example

For example, with slab length of 5 m, slab width of 4 m and bar spacing of 0.2 m, the total rebar length is 209.00.

Inputs used
Slab length 5 m
Slab width 4 m
Bar spacing 0.2 m
Results
Total rebar length 209.00
Number of bars 47

Results are estimates for educational use, not professional advice.

Frequently asked questions

Count bars in each direction as slab dimension divided by spacing, plus one, then multiply by the bar run length and add both directions.

Common spacing is 150–300 mm (0.15–0.3 m), set by the structural design and load.

No. Add extra for overlaps at bar joins, cutting and bends, often around 10–15%.

A grid needs a bar at both edges, so the number of bars is the number of gaps plus one.

Enter the slab length. Enter the slab width. Enter the bar spacing. Read off your total rebar length, together with number of bars — the calculator updates automatically, with no button to press.

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