Calculating your total rebar length is straightforward once you know the Rebar formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Rebar Calculator.
What is Rebar?
The Rebar calculation tells you your total rebar length from a few simple inputs. The figure you are solving for here is the total rebar length.
The Rebar formula
This calculation combines several inputs through a multi-step method rather than a single one-line formula. Enter the values below and the calculator resolves each step in order. The inputs it needs are:
- Slab length — a value measured in m. Example: 5 m.
- Slab width — a value measured in m. Example: 4 m.
- Bar spacing — a value measured in m. Example: 0.2 m.
How to calculate it step by step
- Write down the slab length (for example, 5 m).
- Write down the slab width (for example, 4 m).
- Write down the bar spacing (for example, 0.2 m).
- Apply the formula above to get your total rebar length.
- Double-check the result with the Rebar Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Slab length | 5 m |
| Slab width | 4 m |
| Bar spacing | 0.2 m |
| Total rebar length | 209.00 |
| Number of bars | 47 |
With slab length of 5 m, slab width of 4 m and bar spacing of 0.2 m, the total rebar length works out to 209.00.
Example 2
With slab length of 10 m, slab width of 4 m and bar spacing of 0.2 m, the total rebar length works out to 414.00.
| Result | Value |
|---|---|
| Total rebar length | 414.00 |
| Number of bars | 72 |
Example 3
With slab length of 2.5 m, slab width of 4 m and bar spacing of 0.2 m, the total rebar length works out to 104.50.
| Result | Value |
|---|---|
| Total rebar length | 104.50 |
| Number of bars | 34 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Rebar Calculator does it instantly, for free, with the formula and a worked example built in.
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