Rebar Calculator
Rebar length and tie count for a slab.
Enter your values
Enter the slab length in ft.
Enter the slab width in ft.
Enter the grid spacing in inches.
Enter the price per foot in $.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Total rebar length
- 431.2 ft
- Bars lengthwise
- 10
- Bars widthwise
- 16
- Tie wire intersections
- 160
- Estimated cost
- $366.52
Quick answer
Rebar count comes from slab dimensions divided by grid spacing in each direction, plus overlap allowance.
At a glance
| What it does | Rebar length and tie count for a slab. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Slab length, Slab width, Grid spacing, Price per foot |
| Main output | Total rebar length |
| Cost | Free — no sign-up, no download |
How to use the Rebar Calculator
- 1Enter slab length and width.
- 2Choose grid spacing (12, 16 or 18 inches).
- 3Order 10% extra for laps.
Inputs explained
- Slab length(ft)
- Enter the slab length in ft.
- Slab width(ft)
- Enter the slab width in ft.
- Grid spacing(inches)
- Enter the grid spacing in inches.
- Price per foot($)
- Enter the price per foot in $.
Worked example
Using the values the calculator loads with:
Inputs
- Slab length20 ft
- Slab width12 ft
- Grid spacing16 inches
- Price per foot0.85 $
Results
- Total rebar length431.2 ft
- Bars lengthwise10
- Bars widthwise16
- Tie wire intersections160
- Estimated cost$366.52
Frequently asked questions
How much overlap at splices?
At least 40 bar diameters — about 20 inches for #4 rebar.
Where should rebar sit?
In the middle third of the slab, on chairs, not on the ground.
What do I need to enter into the Rebar Calculator?
Just 4 values: slab length, slab width, grid spacing, price per foot. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Rebar Calculator work out the answer?
Rebar count comes from slab dimensions divided by grid spacing in each direction, plus overlap allowance. The working is shown step by step so you can verify the result by hand.
Is the Rebar Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.