Rebar Calculator
Calculate how many meters of rebar you need for a reinforcement grid in a slab or foundation.
How to use the calculator
- Enter the length and width of the slab or foundation to be reinforced.
- Enter the desired center-to-center spacing between rebar (20–25 cm is common for lighter slabs, tighter for load-bearing structures — always check building codes or consult a professional for load-bearing structures).
- The calculator shows the number of bars in each direction and the total rebar length.
How is it calculated?
The number of bars in each direction is calculated from the opposite dimension divided by the spacing, plus one extra bar to cover both edges. Total length is the sum of all bars in both directions (a single-layer grid, standard for most slabs).
Frequently asked questions
What spacing should I use?
It depends on what the structure needs to bear. For simple, non-load-bearing slabs (like a patio slab), 20–25 cm is common, while load-bearing structures require calculated sizing from a professional.
Does the calculator account for one or two layers?
The calculation shows a single grid (reinforcement in both directions in one plane). Many structures use two layers of rebar mesh (top and bottom) — in that case, double the total length you need.
Is this enough to plan a construction project?
No, this is only a rough material estimate for private, simple projects. For anything load-bearing or requiring a building permit, use a qualified professional for correct sizing.