Construction & Materials
Rebar Calculator
Rebar: rebar Calculator works out bar count and total linear length from the slab dimensions, bar spacing, edge cover and bar length you enter; it excludes lap splices. Worked through below with real figures, and the calculator repeats the working on your own inputs — free, on-device, instant.
Enter your slab length, slab width, bar spacing and edge cover and Rebar Calculator works out the bar count and total linear length with your slab size, bar spacing, edge cover and grid direction — fast, free and private, with no sign-up or uploads.
Estimate only — not a structural design. Bar count and length depend on the slab size, spacing, cover and bar length you enter and exclude lap splices, bends and engineering requirements; confirm with a qualified engineer.
About this calculator
Rebar Calculator works out bar count and total linear length from the slab dimensions, bar spacing, edge cover and bar length you enter; it excludes lap splices. It matters before you buy: a clean volume estimate plus a waste allowance beats a guess every time. Worked below as A slab needing rebar on a 200 mm grid over 3 m × 4 m uses ~16 bars one way and ~21 the other — roughly 127 linear metres plus laps. — and the calculator on this page repeats exactly that working for your inputs, instantly, and offline after load.
How to use
- Enter the reinforced slab length in feet.
- Enter the reinforced slab width in feet.
- Enter the bar spacing, edge cover, and bar length, then pick the grid.
- Tap Calculate to see total linear feet, bars, and piece count.
Why use the Rebar Calculator
Instant
Every quantity is worked out on your device the moment you tap Calculate.
Private
The numbers you enter stay in your browser and are never uploaded or saved.
Free
No signup, no paywall, and no ads placed inside your results.
Works offline
Once the page has loaded it keeps working on a weak or dropped connection.
Mobile-first
Laid out for phones and tablets on site just as much as for desktops.
Planning estimates
Results are simplified planning estimates; real material needs vary by product size, waste, layout, local codes, and site conditions, so confirm before you buy or build.
Common uses
Use it when laying out a reinforcing grid
Use it when reducing offcut waste
Use it when estimating total rebar length
Use it for working out bar spacing and count
Use it when planning slab reinforcement
Use it before a trip to the supply store
Technical notes
Rebar Calculator works out bar count and total linear length from the slab dimensions, bar spacing, edge cover and bar length you enter; it excludes lap splices.
Estimates bar count and total length from the spacing, cover and bar length you enter; it excludes lap splices and is not a structural design.
Nothing you type is uploaded — the calculation happens entirely on your device.
Worked example
A slab needing rebar on a 200 mm grid over 3 m × 4 m uses ~16 bars one way and ~21 the other — roughly 127 linear metres plus laps.
FAQ
Does this replace structural design?
No. It is a quantity estimate for planning; bar size, spacing, and cover must follow an engineer or local code.
Does the Rebar Calculator send my slab size anywhere?
No. The Rebar Calculator runs in your browser and the slab figures are never uploaded.
What is edge cover?
Edge cover is the clear distance from the slab edge to the first bar, kept inside the slab on each side.
What is the difference between one-way and two-way?
One-way places bars in a single direction; two-way adds a second set across it for a grid.